Hypomyelination with brainstem and spinal cord involvement and leg spasticity

An autosomal recessive leukoencephalopathy characterized by onset in the first year of life of severe spasticity, mainly affecting the lower limbs and resulting in an inability to achieve independent ambulation. Affected individuals show delayed motor development and nystagmus; some may have mild intellectual disability. Brain MRI shows hypomyelination and white matter lesions in the cerebrum, brainstem, cerebellum, and spinal cord.

Spinocerebellar ataxia 21

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA21 is characterized by onset in the first decades of life of slowly progressive relatively mild cerebellar ataxia associated with slight extrapyramidal features predominant in older patients and cognitive impairment predominant in younger patients.

Dystonia, childhood-onset, with optic atrophy and basal ganglia abnormalities

An autosomal recessive neurologic disorder characterized by childhood-onset dystonia, basal ganglia degeneration and optic atrophy with decreased visual acuity. Dystonia is defined by the presence of sustained involuntary muscle contraction, often leading to abnormal postures. DYTOABG severity is variable, and some patients lose independent ambulation.

Frontotemporal dementia 2

A form of dementia characterized by pathologic finding of frontotemporal lobar degeneration, presenile dementia with behavioral changes, deterioration of cognitive capacities and loss of memory. Gestural apraxia, parkinsonism, visual loss, and visual hallucinations are present in 25 to 40% of patients.

Dentatorubral-pallidoluysian atrophy

Autosomal dominant neurodegenerative disorder characterized by a loss of neurons in the dentate nucleus, rubrum, glogus pallidus and Luys'body. Clinical features are myoclonus epilepsy, dementia, and cerebellar ataxia. Onset of the disease occurs usually in the second decade of life and death in the fourth.

Leber hereditary optic neuropathy

A maternally inherited form of Leber hereditary optic neuropathy, a mitochondrial disease resulting in bilateral painless loss of central vision due to selective degeneration of the retinal ganglion cells and their axons. The disorder shows incomplete penetrance and male predominance. Cardiac conduction defects and neurological defects have also been described in some LHON patients. LHON results from primary mitochondrial DNA mutations affecting the respiratory chain complexes.

Spinocerebellar ataxia 3

Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to cerebellum degeneration with variable involvement of the brainstem and spinal cord. SCA3 belongs to the autosomal dominant cerebellar ataxias type I (ADCA I) which are characterized by cerebellar ataxia in combination with additional clinical features like optic atrophy, ophthalmoplegia, bulbar and extrapyramidal signs, peripheral neuropathy and dementia. The molecular defect in SCA3 is the a CAG repeat expansion in ATX3 coding region. Longer expansions result in earlier onset and more severe clinical manifestations of the disease.

Ataxia-pancytopenia syndrome

An autosomal dominant disorder characterized by cerebellar ataxia, variable hematologic cytopenias, and predisposition to bone marrow failure and myeloid leukemia.

Barrett esophagus

A condition characterized by a metaplastic change in which normal esophageal squamous epithelium is replaced by a columnar and intestinal-type epithelium. Patients with Barrett esophagus have an increased risk of esophageal adenocarcinoma. The main cause of Barrett esophagus is gastroesophageal reflux. The retrograde movement of acid and bile salts from the stomach into the esophagus causes prolonged injury to the esophageal epithelium and induces chronic esophagitis, which in turn is believed to trigger the pathologic changes.

Neuropathy, ataxia, and retinitis pigmentosa

A syndrome characterized by variable combination of developmental delay, psychomotor retardation, hearing loss, optic atrophy and retinitis pigmentosa, dementia, seizures, ataxia, proximal neurogenic muscle weakness, and sensory neuropathy.

Hydrocephalus, congenital, 1

A form of congenital hydrocephalus, a disease characterized by onset in utero of enlarged ventricles due to accumulation of ventricular cerebrospinal fluid. Affected individuals may have neurologic impairment. HYC1 inheritance is autosomal recessive.

Canavan disease

A rare neurodegenerative condition of infancy or childhood characterized by white matter vacuolization and demyelination that gives rise to a spongy appearance. The clinical features are onset in early infancy, atonia of neck muscles, hypotonia, hyperextension of legs and flexion of arms, blindness, severe mental defect, megalocephaly, and death by 18 months on the average.

Cerebral amyloid angiopathy, ITM2B-related 1

A disorder characterized by amyloid deposition in the walls of cerebral blood vessels and neurodegeneration in the central nervous system. Cerebral amyloid angiopathy, non-neuritic and perivascular plaques and neurofibrillary tangles are the predominant pathological lesions. Clinical features include progressive mental deterioration, spasticity and muscular rigidity.

Leukodystrophy, hypomyelinating, 28

A form of hypomyelinating leukodystrophy, a group of heterogeneous disorders characterized by persistent deficit of myelin observed on brain imaging. HLD28 is an autosomal recessive form characterized by developmental delay and nystagmus in infancy, followed by significant learning disabilities and progressive motor deterioration within the first decade.

Leukodystrophy, hypomyelinating, 1

An X-linked recessive disorder of the central nervous system in which myelin is not formed properly. Clinically characterized by nystagmus, spastic quadriplegia, ataxia, and developmental delay.

Spinal muscular atrophy 1

A form of spinal muscular atrophy, a group of neuromuscular disorder characterized by degeneration of the anterior horn cells of the spinal cord, leading to symmetrical muscle weakness and atrophy. Autosomal recessive forms are classified according to the age of onset, the maximum muscular activity achieved, and survivorship. The severity of the disease is mainly determined by the copy number of SMN2, a copy gene which predominantly produces exon 7-skipped transcripts and only low amount of full-length transcripts that encode for a protein identical to SMN1. Only about 4% of SMA patients bear one SMN1 copy with an intragenic mutation. SMA1 is a severe form, with onset before 6 months of age. SMA1 patients never achieve the ability to sit.

Spinocerebellar ataxia, autosomal recessive, 13

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCAR13 is characterized by delayed psychomotor development beginning in infancy. Affected individuals show mild to profound intellectual disability with poor or absent speech as well as gait and stance ataxia and hyperreflexia.

Aicardi-Goutieres syndrome 8

A form of Aicardi-Goutieres syndrome, a genetically heterogeneous disease characterized by cerebral atrophy, leukoencephalopathy, intracranial calcifications, chronic cerebrospinal fluid (CSF) lymphocytosis, increased CSF alpha-interferon, and negative serologic investigations for common prenatal infection. Clinical features as thrombocytopenia, hepatosplenomegaly and elevated hepatic transaminases along with intermittent fever may erroneously suggest an infective process. Severe neurological dysfunctions manifest in infancy as progressive microcephaly, spasticity, dystonic posturing and profound psychomotor retardation. Death often occurs in early childhood. AGS8 inheritance is autosomal recessive.

Aicardi-Goutieres syndrome 1

A form of Aicardi-Goutieres syndrome, a genetically heterogeneous disease characterized by cerebral atrophy, leukoencephalopathy, intracranial calcifications, chronic cerebrospinal fluid (CSF) lymphocytosis, increased CSF alpha-interferon, and negative serologic investigations for common prenatal infection. Clinical features as thrombocytopenia, hepatosplenomegaly and elevated hepatic transaminases along with intermittent fever may erroneously suggest an infective process. Severe neurological dysfunctions manifest in infancy as progressive microcephaly, spasticity, dystonic posturing and profound psychomotor retardation. Death often occurs in early childhood.

Aicardi-Goutieres syndrome 3

A form of Aicardi-Goutieres syndrome, a genetically heterogeneous disease characterized by cerebral atrophy, leukoencephalopathy, intracranial calcifications, chronic cerebrospinal fluid (CSF) lymphocytosis, increased CSF alpha-interferon, and negative serologic investigations for common prenatal infection. Clinical features as thrombocytopenia, hepatosplenomegaly and elevated hepatic transaminases along with intermittent fever may erroneously suggest an infective process. Severe neurological dysfunctions manifest in infancy as progressive microcephaly, spasticity, dystonic posturing and profound psychomotor retardation. Death often occurs in early childhood.

Spastic paraplegia 61, autosomal recessive

A complicated form of spastic paraplegia with polysensory and motor neuropathy. Spastic paraplegia is a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Spastic paraplegia 62, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Friedreich ataxia

Autosomal recessive, progressive degenerative disease characterized by neurodegeneration and cardiomyopathy it is the most common inherited ataxia. The disorder is usually manifest before adolescence and is generally characterized by incoordination of limb movements, dysarthria, nystagmus, diminished or absent tendon reflexes, Babinski sign, impairment of position and vibratory senses, scoliosis, pes cavus, and hammer toe. In most patients, FRDA is due to GAA triplet repeat expansions in the first intron of the frataxin gene. But in some cases the disease is due to mutations in the coding region.

Spastic paraplegia 73, autosomal dominant

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Spastic paraplegia 20, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. SPG20 is characterized by dysarthria, distal amyotrophy, mild developmental delay and short stature.

Abetalipoproteinemia

An autosomal recessive disorder of lipoprotein metabolism. Affected individuals produce virtually no circulating apolipoprotein B-containing lipoproteins (chylomicrons, VLDL, LDL, lipoprotein(A)). Malabsorption of the antioxidant vitamin E occurs, leading to spinocerebellar and retinal degeneration.

Congenital anomalies of the kidney and urinary tract 1

A disorder encompassing a broad spectrum of renal and urinary tract malformations that include renal agenesis, kidney hypodysplasia, multicystic kidney dysplasia, duplex collecting system, posterior urethral valves and ureter abnormalities. Congenital anomalies of kidney and urinary tract are the commonest cause of chronic kidney disease in children.

Leukodystrophy, hypomyelinating, 7, with or without oligodontia and/or hypogonadotropic hypogonadism

An autosomal recessive neurodegenerative disorder characterized by childhood onset of progressive motor decline manifest as spasticity, ataxia, tremor, and cerebellar signs, as well as mild cognitive regression. Other features may include hypodontia or oligodontia and hypogonadotropic hypogonadism. There is considerable inter- and intrafamilial variability.

Pontocerebellar hypoplasia 1D

An autosomal recessive neurologic disorder with onset at birth or in infancy, and characterized by progressive axonal motor neuronopathy, severe generalized hypotonia, respiratory insufficiency, and cerebellar atrophy. Death in childhood may occur.

Spinocerebellar ataxia 26

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord.

Leukoencephalopathy, cystic, without megalencephaly

An infantile-onset syndrome of cerebral leukoencephalopathy. Affected newborns develop microcephaly and neurologic abnormalities including psychomotor impairment, seizures and sensorineural hearing impairment. The brain shows multifocal white matter lesions, anterior temporal lobe subcortical cysts, pericystic abnormal myelination, ventriculomegaly and intracranial calcifications.

Neurodevelopmental disorder with spastic paraplegia and microcephaly

An autosomal recessive syndrome characterized by severe psychomotor developmental delay, dysarthria, walking difficulties, moderately to severely impaired intellectual development, poor or absent speech, and progressive microcephaly.

Alexander disease

A rare disorder of the central nervous system. The most common form affects infants and young children, and is characterized by progressive failure of central myelination, usually leading to death within the first decade. Infants with Alexander disease develop a leukodystrophy with macrocephaly, seizures, and psychomotor retardation. Patients with juvenile or adult forms typically experience ataxia, bulbar signs and spasticity, and a more slowly progressive course. Histologically, Alexander disease is characterized by Rosenthal fibers, homogeneous eosinophilic inclusions in astrocytes.

Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 2

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCAN2 is an autosomal recessive form associated with peripheral neuropathy and elevated serum alpha-fetoprotein, immunoglobulins and, less commonly, creatine kinase levels. Some SCAN2 patients manifest oculomotor apraxia.

Pontocerebellar hypoplasia 1A

A form of pontocerebellar hypoplasia, a disorder characterized by structural defects of the pons and cerebellum, evident upon brain imaging. PCH1A is an autosomal recessive form characterized by an abnormally small cerebellum and brainstem, central and peripheral motor dysfunction from birth, gliosis and spinal cord anterior horn cells degeneration resembling infantile spinal muscular atrophy. Additional features include muscle hypotonia, congenital contractures and respiratory insufficiency that is evident at birth.

Pontocerebellar hypoplasia 1B

A severe autosomal recessive neurologic disorder characterized by a combination of cerebellar and spinal motor neuron degeneration beginning at birth. There is diffuse muscle weakness, progressive microcephaly, global developmental delay, and brainstem involvement.

Pontocerebellar hypoplasia 1C

A severe autosomal recessive neurodegenerative disease characterized by cerebellar and corpus callosum hypoplasia, abnormal myelination of the central nervous system, and spinal motor neuron disease. Affected individuals manifest failure to thrive, severe muscle weakness, spasticity and psychomotor retardation. Vision and hearing are impaired.

Spinocerebellar ataxia 37

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA37 is an autosomal dominant form characterized by adult-onset of slowly progressive gait instability, frequent falls, and dysarthria associated with cerebellar atrophy on brain imaging.

Cerebellar ataxia, impaired intellectual development, and dysequilibrium syndrome 1

An autosomal recessive, congenital, non-progressive cerebellar ataxia associated with disturbed equilibrium, delayed ambulation, intellectual disability, cerebellar hypoplasia and mild cerebral gyral simplification. Additional features include short stature, strabismus, pes planus and, rarely, seizures.

Amyotrophic lateral sclerosis 2

A neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. Sensory abnormalities are absent. The pathologic hallmarks of the disease include pallor of the corticospinal tract due to loss of motor neurons, presence of ubiquitin-positive inclusions within surviving motor neurons, and deposition of pathologic aggregates. The etiology of amyotrophic lateral sclerosis is likely to be multifactorial, involving both genetic and environmental factors. The disease is inherited in 5-10% of the cases.

Cutis laxa, autosomal recessive, 3A

A syndrome characterized by facial dysmorphism with a progeroid appearance, large and late-closing fontanel, cutis laxa, joint hyperlaxity, athetoid movements and hyperreflexia, pre- and postnatal growth retardation, intellectual deficit, developmental delay, and ophthalmologic abnormalities.

GM2-gangliosidosis AB

An autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. It is characterized by GM2 gangliosides accumulation in the presence of both normal hexosaminidase A and B.

Lichtenstein-Knorr syndrome

An autosomal recessive neurologic disorder characterized by progressive cerebellar ataxia and severe progressive sensorineural hearing loss.

Spastic paraplegia 80, autosomal dominant

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Neuropathy, hereditary sensory and autonomic, 9, with developmental delay

A form of hereditary sensory and autonomic neuropathy, a genetically and clinically heterogeneous group of disorders characterized by degeneration of dorsal root and autonomic ganglion cells, and by sensory and/or autonomic abnormalities. HSAN9 is characterized by global developmental delay and intellectual disability, axial and appendicular hypotonia, dysarthria, and an abnormal gait that is often described as ataxic. Other features may include peripheral neuropathy, hyporeflexia, and autonomic dysfunction. Affected individuals also have dysmorphic features, thin corpus callosum on brain imaging, and episodes of central apnea, which may be fatal.

Neuronopathy, distal hereditary motor, autosomal recessive 1

A form of distal hereditary motor neuronopathy, a heterogeneous group of neuromuscular disorders caused by selective degeneration of motor neurons in the anterior horn of the spinal cord, without sensory deficit in the posterior horn. The overall clinical picture consists of a classical distal muscular atrophy syndrome in the legs without clinical sensory loss. The disease starts with weakness and wasting of distal muscles of the anterior tibial and peroneal compartments of the legs. Later on, weakness and atrophy may expand to the proximal muscles of the lower limbs and/or to the distal upper limbs.

Neuronopathy, distal hereditary motor, autosomal dominant 9

A form of distal hereditary motor neuronopathy, a heterogeneous group of neuromuscular disorders caused by selective degeneration of motor neurons in the anterior horn of the spinal cord, without sensory deficit in the posterior horn. The overall clinical picture consists of a classical distal muscular atrophy syndrome in the legs without clinical sensory loss. The disease starts with weakness and wasting of distal muscles of the anterior tibial and peroneal compartments of the legs. Later on, weakness and atrophy may expand to the proximal muscles of the lower limbs and/or to the distal upper limbs. HMND9 is characterized by juvenile onset of slowly progressive distal muscle weakness and atrophy affecting both the lower and upper limbs.

Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination

An autosomal recessive neurodevelopmental disorder with onset at birth or in early infancy, and characterized by microcephaly, short stature, severe global developmental delay, progressive spasticity, and epilepsy. Brain imaging shows delayed myelination, hypomyelination, enlarged ventricles, and cerebellar atrophy.

Neurodegeneration, childhood-onset, with multisystem involvement due to mitochondrial dysfunction

An autosomal recessive disorder characterized primarily by global developmental delay and variably impaired intellectual development with speech delay apparent from infancy. Affected individuals have hypotonia, poor feeding, poor overall growth, and respiratory distress early in life. Other features include visual impairment due to optic atrophy, sensorineural hearing loss, and neuromuscular abnormalities. Features suggestive of a mitochondrial disorder include cataracts, cardiomyopathy, diabetes mellitus, combined oxidative phosphorylation deficiency, and increased lactate. Some patients develop seizures, some have dysmorphic facial features, and some have non-specific abnormalities on brain imaging. Death in childhood may occur.

Neurodegeneration, childhood-onset, with ataxia, tremor, optic atrophy, and cognitive decline

An autosomal recessive neurodegenerative disease characterized by progressive ataxia, tremor, cognitive decline, dysphagia, optic atrophy, dysarthria, as well as urinary and bowel incontinence. Brain MRI demonstrates cerebellar atrophy and leukoencephalopathy.

Hemochromatosis 5

A disorder of iron metabolism characterized by iron overload. Excess iron is deposited in a variety of organs leading to their failure, and resulting in serious illnesses including cirrhosis, hepatomas, diabetes, cardiomyopathy, arthritis, and hypogonadotropic hypogonadism. Severe effects of the disease usually do not appear until after decades of progressive iron loading.

Neurodegeneration with brain iron accumulation 1

Autosomal recessive neurodegenerative disorder associated with iron accumulation in the brain, primarily in the basal ganglia. Clinical manifestations include progressive muscle spasticity, hyperreflexia, muscle rigidity, dystonia, dysarthria, and intellectual deterioration which progresses to severe dementia over several years. It is clinically classified into classic, atypical, and intermediate phenotypes. Classic forms present with onset in first decade, rapid progression, loss of independent ambulation within 15 years. Atypical forms have onset in second decade, slow progression, maintenance of independent ambulation up to 40 years later. Intermediate forms manifest onset in first decade with slow progression or onset in second decade with rapid progression. Patients with early onset tend to also develop pigmentary retinopathy, whereas those with later onset tend to also have speech disorders and psychiatric features. All patients have the 'eye of the tiger' sign on brain MRI.

Neurodegeneration and seizures due to copper transport defect

An autosomal recessive disorder of copper metabolism characterized by global developmental delay, seizures, cortical and cerebellar atrophy, and axial hypotonia. Death in infancy may occur.

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 3

A disorder characterized by progressive weakness of ocular muscles and levator muscle of the upper eyelid. In a minority of cases, it is associated with skeletal myopathy, which predominantly involves axial or proximal muscles and which causes abnormal fatigability and even permanent muscle weakness. Ragged-red fibers and atrophy are found on muscle biopsy. A large proportion of chronic ophthalmoplegias are associated with other symptoms, leading to a multisystemic pattern of this disease. Additional symptoms are variable, and may include cataracts, hearing loss, sensory axonal neuropathy, ataxia, depression, hypogonadism, and parkinsonism.

Combined oxidative phosphorylation deficiency 8

A mitochondrial disease characterized by a lethal infantile hypertrophic cardiomyopathy, generalized muscle dysfunction and some neurologic involvement. The liver is not affected.

Leukodystrophy, hypomyelinating, 8, with or without oligodontia and/or hypogonadotropic hypogonadism

An autosomal recessive neurodegenerative disorder characterized by early childhood onset of cerebellar ataxia and mild intellectual disabilities associated with diffuse hypomyelination apparent on brain MRI. Variable features include oligodontia and/or hypogonadotropic hypogonadism.

Leukodystrophy, hypomyelinating, 2

An autosomal recessive hypomyelinating leukodystrophy with symptoms of Pelizaeus-Merzbacher disease. Clinically characterized by nystagmus, impaired motor development, ataxia, choreoathetotic movements, dysarthria, and progressive spasticity.

Leukodystrophy, hypomyelinating, 12

An autosomal recessive neurologic disorder characterized by developmental delay, spasticity, truncal hypotonia, acquired microcephaly, intellectual disability with variable seizure disorder, accompanied by thin corpus callosum, paucity of white matter and delayed myelination.

Joubert syndrome 14

An autosomal recessive disorder characterized by severe intellectual disability, hypotonia, breathing abnormalities in infancy, and dysmorphic facial features. Neuroradiologically, it is characterized by cerebellar vermian hypoplasia/aplasia, thickened and reoriented superior cerebellar peduncles, and an abnormally large interpeduncular fossa, giving the appearance of a molar tooth on transaxial slices (molar tooth sign). Additional variable features include renal disease, abnormal eye movements, and postaxial polydactyly.

GM2-gangliosidosis 1

An autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. It is characterized by GM2 gangliosides accumulation in the absence of HEXA activity, leading to neurodegeneration and, in the infantile form, death in early childhood. It exists in several forms: infantile (most common and most severe), juvenile and adult (late-onset).

Charcot-Marie-Tooth disease, axonal, type 2N

An axonal form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies (designated CMT1 when they are dominantly inherited) and primary peripheral axonal neuropathies (CMT2). Neuropathies of the CMT2 group are characterized by signs of axonal degeneration in the absence of obvious myelin alterations, normal or slightly reduced nerve conduction velocities, and progressive distal muscle weakness and atrophy.

Spinocerebellar ataxia, autosomal recessive, 31

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCAR30 is characterized by global developmental delay, hypotonia, variably impaired intellectual and language development, ataxic gait, tremor, and dysarthria. Most affected individuals have optic atrophy. Additional features may include retinitis pigmentosa, sensorineural deafness, dysmorphic facial features, and possibly endocrine dysfunction.

Spinocerebellar ataxia, autosomal recessive, 27

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCAR27 is a progressive disease characterized by gait difficulties, eye movement abnormalities, dysarthria, and difficulty writing. Some patients may lose independent ambulation. Additional features include spasticity of the lower limbs and cognitive impairment.

Spinocerebellar ataxia, autosomal recessive, 23

A form of spinocerebellar ataxia, a clinically and genetically heterogeneous group of cerebellar disorders due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCAR23 patients manifest epilepsy, intellectual disability, and gait ataxia.

Spinocerebellar ataxia 15

Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA15 is an autosomal dominant cerebellar ataxia (ADCA). It is very slow progressing form with a wide range of onset, ranging from childhood to adult. Most patients remain ambulatory.

Frontotemporal dementia and/or amyotrophic lateral sclerosis 2

A neurodegenerative disorder characterized by frontotemporal dementia and/or amyotrophic lateral sclerosis in affected individuals. There is high intrafamilial variation. Frontotemporal dementia is characterized by frontal and temporal lobe atrophy associated with neuronal loss, gliosis, and dementia. Patients exhibit progressive changes in social, behavioral, and/or language function. Amyotrophic lateral sclerosis is characterized by the death of motor neurons in the brain, brainstem, and spinal cord, resulting in fatal paralysis.

Androgen insensitivity syndrome

An X-linked recessive form of pseudohermaphroditism due end-organ resistance to androgen. Affected males have female external genitalia, female breast development, blind vagina, absent uterus and female adnexa, and abdominal or inguinal testes, despite a normal 46,XY karyotype.

Spastic paraplegia 81, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. SPG81 is a complicated form characterized by white matter abnormalities, hypomyelination with progressive white matter loss, delayed motor development, progressive spasticity, and impaired intellectual development and speech delay. Additional features may include bifid uvula, microcephaly, seizures, and variable ocular anomalies.

Spastic paraplegia 6, autosomal dominant

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body.

Spastic paraplegia 30A, autosomal dominant

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. Some SPG30A patients have a pure form of the disorder, limited to spastic paraplegia, whereas others may have a complicated form that includes additional features such as cognitive dysfunction, learning disabilities, peripheral sensorimotor neuropathy, urinary sphincter problems, and/or cerebellar atrophy. SPG30A is characterized by onset in the first or second decades of unsteady spastic gait and hyperreflexia of the lower limbs. Inheritance is autosomal dominant.

Spastic ataxia 2, autosomal recessive

A neurologic disorder characterized by cerebellar ataxia, dysarthria, and variable spasticity of the lower limbs. Cognition is not affected.

Ribose 5-phosphate isomerase deficiency

An autosomal recessive inborn error of polyols metabolism characterized by highly elevated level of ribitol and arabitol in brain and body fluids. Clinical features include leukoencephalopathy, psychomotor retardation from early life, neurologic regression, and a mild sensorimotor neuropathy.

Peroxisome biogenesis disorder complementation group 9

A peroxisomal disorder arising from a failure of protein import into the peroxisomal membrane or matrix. The peroxisome biogenesis disorders (PBD group) are genetically heterogeneous with at least 14 distinct genetic groups as concluded from complementation studies. Include disorders are: Zellweger syndrome (ZWS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and classical rhizomelic chondrodysplasia punctata (RCDP). ZWS, NALD and IRD are distinct from RCDP and constitute a clinical continuum of overlapping phenotypes known as the Zellweger spectrum (PBD-ZSS).

Peroxisome biogenesis disorder complementation group 4

A peroxisomal disorder arising from a failure of protein import into the peroxisomal membrane or matrix. The peroxisome biogenesis disorders (PBD group) are genetically heterogeneous with at least 14 distinct genetic groups as concluded from complementation studies. Include disorders are: Zellweger syndrome (ZWS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and classical rhizomelic chondrodysplasia punctata (RCDP). ZWS, NALD and IRD are distinct from RCDP and constitute a clinical continuum of overlapping phenotypes known as the Zellweger spectrum (PBD-ZSS).

Peroxisome biogenesis disorder complementation group 3

A peroxisomal disorder arising from a failure of protein import into the peroxisomal membrane or matrix. The peroxisome biogenesis disorders (PBD group) are genetically heterogeneous with at least 14 distinct genetic groups as concluded from complementation studies. Include disorders are: Zellweger syndrome (ZWS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and classical rhizomelic chondrodysplasia punctata (RCDP). ZWS, NALD and IRD are distinct from RCDP and constitute a clinical continuum of overlapping phenotypes known as the Zellweger spectrum (PBD-ZSS).

Peroxisome biogenesis disorder complementation group 1

A peroxisomal disorder arising from a failure of protein import into the peroxisomal membrane or matrix. The peroxisome biogenesis disorders (PBD group) are genetically heterogeneous with at least 14 distinct genetic groups as concluded from complementation studies. Include disorders are: Zellweger syndrome (ZWS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and classical rhizomelic chondrodysplasia punctata (RCDP). ZWS, NALD and IRD are distinct from RCDP and constitute a clinical continuum of overlapping phenotypes known as the Zellweger spectrum (PBD-ZSS).

PEHO syndrome

An autosomal recessive syndrome characterized by progressive encephalopathy, lack of psychomotor development, severe intellectual disability, early onset epileptic seizures, optic nerve/cerebellar atrophy, pedal edema, and early death.

Spinocerebellar ataxia 28

Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA28 is an autosomal dominant cerebellar ataxia (ADCA) with a slow progressive course and no evidence of sensory involvement or cognitive impairment.

Neuronopathy, hereditary motor, autosomal recessive 7

An autosomal recessive, neuromyopathic disorder that manifests in childhood or adulthood with proximal and distal muscle weakness predominantly of the lower limbs. Affected individuals have difficulty climbing stairs and problems standing on the heels. Most patients have foot deformities, and some may have leg muscle atrophy. Muscle biopsy and electrophysiologic studies are consistent with both a myopathic process and an axonal motor neuropathy.

Neuronopathy, distal hereditary motor, autosomal dominant 7

A form of distal hereditary motor neuronopathy, a heterogeneous group of neuromuscular disorders caused by selective degeneration of motor neurons in the anterior horn of the spinal cord, without sensory deficit in the posterior horn. The overall clinical picture consists of a classical distal muscular atrophy syndrome in the legs without clinical sensory loss. The disease starts with weakness and wasting of distal muscles of the anterior tibial and peroneal compartments of the legs. Later on, weakness and atrophy may expand to the proximal muscles of the lower limbs and/or to the distal upper limbs. HMND7 is characterized by onset in the second decade of progressive distal muscle wasting and weakness affecting the upper and lower limbs and resulting in walking difficulties and hand grip. There is significant muscle atrophy of the hands and lower limbs. The disorder is associated with vocal cord paresis due to involvement of the tenth cranial nerve.

Charcot-Marie-Tooth disease, axonal, type 2D

A dominant axonal form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies (designated CMT1 when they are dominantly inherited) and primary peripheral axonal neuropathies (CMT2). Neuropathies of the CMT2 group are characterized by signs of axonal degeneration in the absence of obvious myelin alterations, normal or slightly reduced nerve conduction velocities, and progressive distal muscle weakness and atrophy.

Neurodegeneration with brain iron accumulation 6

A neurodegenerative disorder associated with iron accumulation in the brain, primarily in the basal ganglia. It is characterized by progressive motor and cognitive dysfunction beginning in childhood or young adulthood. Patients show extrapyramidal motor signs, such as spasticity, dystonia, and parkinsonism.

Hyperferritinemia with or without cataract

An autosomal dominant disease characterized by elevated level of ferritin in serum and tissues, and early-onset bilateral cataract. Cataracts may be subclinical in some patients.

Megalencephalic leukoencephalopathy with subcortical cysts 2A

A neurodegenerative disorder characterized by infantile-onset macrocephaly and later onset of motor deterioration, with ataxia and spasticity, seizures, and cognitive decline of variable severity. The brain appears swollen on magnetic resonance imaging with white-matter abnormalities and subcortical cysts, in all stages of the disease.

Spastic paraplegia 21, autosomal recessive

A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. SPG21 is associated with dementia and other central nervous system abnormalities. Subtle childhood abnormalities may be present, but the main features develop in early adulthood. The disease is slowly progressive, and cerebellar and extrapyramidal signs are also found in patients with advanced disease. Patients have a thin corpus callosum and white-matter abnormalities.

Leukoencephalopathy with vanishing white matter 3

An autosomal recessive brain disease characterized by neurological features including progressive cerebellar ataxia, spasticity, and cognitive deficits. Brain imaging shows abnormal white matter that vanishes over time and is replaced by cerebrospinal fluid. Disease severity ranges from fatal infantile forms to adult forms without neurological deterioration. The disease is progressive with, in most individuals, additional episodes of rapid deterioration following febrile infections or minor head trauma. Death may occurs after a variable period after disease onset, usually following an episode of fever and coma. A subset of affected females with milder forms of the disease who survive to adolescence exhibit ovarian dysfunction. This variant of the disorder is called ovarioleukodystrophy.

Leukoencephalopathy with vanishing white matter 2

An autosomal recessive brain disease characterized by neurological features including progressive cerebellar ataxia, spasticity, and cognitive deficits. Brain imaging shows abnormal white matter that vanishes over time and is replaced by cerebrospinal fluid. Disease severity ranges from fatal infantile forms to adult forms without neurological deterioration. The disease is progressive with, in most individuals, additional episodes of rapid deterioration following febrile infections or minor head trauma. Death may occurs after a variable period after disease onset, usually following an episode of fever and coma. A subset of affected females with milder forms of the disease who survive to adolescence exhibit ovarian dysfunction. This variant of the disorder is called ovarioleukodystrophy.

Leukoencephalopathy with vanishing white matter 1

An autosomal recessive brain disease characterized by neurological features including progressive cerebellar ataxia, spasticity, and cognitive deficits. Brain imaging shows abnormal white matter that vanishes over time and is replaced by cerebrospinal fluid. Disease severity ranges from fatal infantile forms to adult forms without neurological deterioration. The disease is progressive with, in most individuals, additional episodes of rapid deterioration following febrile infections or minor head trauma. Death may occurs after a variable period after disease onset, usually following an episode of fever and coma. A subset of affected females with milder forms of the disease who survive to adolescence exhibit ovarian dysfunction. This variant of the disorder is called ovarioleukodystrophy.