Fumarase deficiency

A severe autosomal recessive metabolic disorder characterized by early-onset hypotonia, profound psychomotor retardation, and brain abnormalities, such as agenesis of the corpus callosum, gyral defects, and ventriculomegaly. Many patients show neonatal distress, metabolic acidosis, and/or encephalopathy.

Leigh syndrome

An early-onset progressive neurodegenerative disorder characterized by the presence of focal, bilateral lesions in one or more areas of the central nervous system including the brainstem, thalamus, basal ganglia, cerebellum and spinal cord. Clinical features depend on which areas of the central nervous system are involved and include subacute onset of psychomotor retardation, hypotonia, ataxia, weakness, vision loss, eye movement abnormalities, seizures, and dysphagia.

Cardiomyopathy, dilated, 2H

A form of dilated cardiomyopathy, a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death. CMD2H is an autosomal recessive form characterized by rapid progression and death in early infancy.

Giant axonal neuropathy 1, autosomal recessive

A severe autosomal recessive sensorimotor neuropathy affecting both the peripheral nerves and the central nervous system. Axonal loss and the presence of giant axonal swellings filled with neurofilaments on nerve biopsies are the hallmarks of this neurodegenerative disorder.

Charcot-Marie-Tooth disease, dominant intermediate C

A 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. The dominant intermediate type C is characterized by clinical and pathologic features intermediate between demyelinating and axonal peripheral neuropathies, and motor median nerve conduction velocities ranging from 25 to 45 m/sec.

Cataracts, growth hormone deficiency, sensory neuropathy, sensorineural hearing loss, and skeletal dysplasia

An autosomal recessive disorder characterized by cataracts, short-stature secondary to growth hormone deficiency, sensorineural hearing deficit, peripheral sensory neuropathy, skeletal dysplasia, scoliosis, and facial dysmorphism.

Usher syndrome 3B

A syndrome characterized by progressive vision and hearing loss during early childhood. Some patients have the so-called 'Charles Bonnet syndrome,' involving decreased visual acuity and vivid visual hallucinations. USH is a genetically heterogeneous condition characterized by the association of retinitis pigmentosa with sensorineural deafness. Age at onset and differences in auditory and vestibular function distinguish Usher syndrome type 1 (USH1), Usher syndrome type 2 (USH2) and Usher syndrome type 3 (USH3). USH3 is characterized by postlingual, progressive hearing loss, variable vestibular dysfunction, and onset of retinitis pigmentosa symptoms, including nyctalopia, constriction of the visual fields, and loss of central visual acuity, usually by the second decade of life.

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

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.

Mitochondrial DNA depletion syndrome 8A

A disorder due to mitochondrial dysfunction characterized by various combinations of neonatal hypotonia, neurological deterioration, respiratory distress, lactic acidosis, and renal tubulopathy.

Coenzyme Q10 deficiency, primary, 7

An autosomal recessive disorder resulting from mitochondrial dysfunction and characterized by decreased levels of coenzyme Q10, and severe cardiac or neurologic symptoms soon after birth, usually resulting in death. Rarely, symptoms may have later onset.

Charcot-Marie-Tooth disease, demyelinating, type 4A

A recessive demyelinating 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). Demyelinating neuropathies are characterized by severely reduced nerve conduction velocities (less than 38 m/sec), segmental demyelination and remyelination with onion bulb formations on nerve biopsy, slowly progressive distal muscle atrophy and weakness, absent deep tendon reflexes, and hollow feet. By convention autosomal recessive forms of demyelinating Charcot-Marie-Tooth disease are designated CMT4. CMT4A is a severe form characterized by early age of onset and rapid progression leading to inability to walk in late childhood or adolescence.

Interstitial lung and liver disease

An autosomal recessive, life-threatening disorder characterized by respiratory insufficiency and progressive liver disease with onset in infancy or early childhood. Clinical features include failure to thrive, hypotonia, intermittent lactic acidosis, aminoaciduria, hypothyroidism, interstitial lung disease, pulmonary alveolar proteinosis, anemia, and liver canalicular cholestasis, steatosis, and iron deposition.

Auditory neuropathy and optic atrophy

An autosomal recessive disease characterized by hearing loss, visual impairment and optic atrophy, with onset in the first or second decades of life. Optic atrophy is caused by degeneration of nerve fibers which arise in the retina and converge to form the optic disk, optic nerve, optic chiasm and optic tracts.

Peroxisome biogenesis disorder 14B

An autosomal recessive peroxisome biogenesis disorder characterized clinically by mild intellectual disability, congenital cataracts, progressive hearing loss, and polyneuropathy. Additionally, recurrent migraine-like episodes following mental stress or physical exertion, not a common feature in peroxisome disorders, are observed.

Peroxisome biogenesis disorder complementation group 14

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).

Charcot-Marie-Tooth disease, demyelinating, type 1B

A dominant demyelinating 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). Demyelinating neuropathies are characterized by severely reduced nerve conduction velocities (less than 38 m/sec), segmental demyelination and remyelination with onion bulb formations on nerve biopsy, slowly progressive distal muscle atrophy and weakness, absent deep tendon reflexes, and hollow feet.

Charcot-Marie-Tooth disease, axonal, type 2A2B

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. CMT2A2B is a severe form with autosomal recessive inheritance.

Amyloidosis, hereditary systemic 4, Finnish type

A form of hereditary systemic amyloidosis, a disorder characterized by amyloid deposition in multiple tissues resulting in a wide clinical spectrum. AMYLD4 is due to gelsolin amyloid deposition and is typically characterized by cranial neuropathy and lattice corneal dystrophy. Most patients have modest involvement of internal organs, but severe systemic disease can develop in some individuals causing peripheral polyneuropathy, amyloid cardiomyopathy, and nephrotic syndrome leading to renal failure. AMYLD4 is usually inherited in an autosomal dominant pattern. However, homozygotes with a more severe phenotype have also been reported.

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.

Neuropathy, hereditary sensory and autonomic, 1C

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 prominent sensory abnormalities with a variable degree of motor and autonomic dysfunction. The neurological phenotype is often complicated by severe infections, osteomyelitis, and amputations. HSAN1C symptoms include loss of touch and vibration in the feet, dysesthesia and severe panmodal sensory loss in the upper and lower limbs, distal lower limb sensory loss with ulceration and osteomyelitis, and distal muscle weakness.

Charcot-Marie-Tooth disease, demyelinating, type 1F

A dominant demyelinating 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). Demyelinating neuropathies are characterized by severely reduced nerve conduction velocities (less than 38 m/sec), segmental demyelination and remyelination with onion bulb formations on nerve biopsy, slowly progressive distal muscle atrophy and weakness, absent deep tendon reflexes, and hollow feet. CMT1F is characterized by onset in infancy or childhood (range 1 to 13 years).

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.

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.

Pyruvate dehydrogenase E1-beta deficiency

An enzymatic defect causing primary lactic acidosis in children. It is associated with a broad clinical spectrum ranging from fatal lactic acidosis in the newborn to chronic neurologic dysfunction with structural abnormalities in the central nervous system without systemic acidosis.

Microcephaly, seizures, and developmental delay

An autosomal recessive neurodevelopmental disorder characterized by infantile-onset seizures, microcephaly, severe intellectual disability and delayed motor milestones with absent speech or only achieving a few words. Most patients also have behavioral problems with hyperactivity. Microcephaly is progressive and without neuronal migration or structural abnormalities, consistent with primary microcephaly.

Hyperornithinemia with gyrate atrophy of choroid and retina

A disorder clinically characterized by a triad of progressive chorioretinal degeneration, early cataract formation, and type II muscle fiber atrophy. Characteristic chorioretinal atrophy with progressive constriction of the visual fields leads to blindness at the latest during the sixth decade of life. Patients generally have normal intelligence.

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.

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.

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

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.

Neuropathy, congenital hypomyelinating, 1, autosomal recessive

A severe degenerating neuropathy that results from a congenital impairment in myelin formation. It is clinically characterized by early onset of hypotonia, areflexia, distal muscle weakness, and very slow nerve conduction velocities (as low as 3m/s). Some patients manifest nearly complete absence of spontaneous limb movements, respiratory distress at birth, and complete absence of myelin shown by electron microscopy of peripheral nerves.

Mitochondrial trifunctional protein deficiency 1

An autosomal recessive metabolic disorder of long-chain fatty acid oxidation, biochemically characterized by loss of all enzyme activities of the mitochondrial trifunctional protein complex. The disease phenotype ranges from a fatal form characterized by early-onset cardiomyopathy, cardiac failure and early death to less severe, late-onset forms with myopathy, recurrent rhabdomyolysis, and sensorimotor axonal neuropathy as key features.

Combined oxidative phosphorylation deficiency 6

A mitochondrial disease resulting in a neurodegenerative disorder characterized by psychomotor delay, hypotonia, areflexia, muscle weakness and wasting. Some patients manifest prenatal ventriculomegaly and severe postnatal encephalomyopathy.

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.

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.

Lipodystrophy, congenital generalized, 2

A form of congenital generalized lipodystrophy, a metabolic disorder characterized by a near complete absence of adipose tissue, extreme insulin resistance, hypertriglyceridemia, hepatic steatosis and early onset of diabetes. Inheritance is autosomal recessive.

Perching syndrome

An autosomal recessive multisystem disorder characterized by global developmental delay, dysmorphic facial features, feeding and respiratory difficulties with poor overall growth, axial hypotonia, and joint contractures. The features are variable, even within families, and may also include retinitis pigmentosa, cardiac or genitourinary anomalies, and abnormal sweating.

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.

Brachyolmia 3

A form of brachyolmia, a clinically and genetically heterogeneous skeletal dysplasia primarily affecting the spine and characterized by a short trunk, short stature, and platyspondyly. BCYM3 is an autosomal dominant form with severe scoliosis with or without kyphosis, and flattened irregular cervical vertebrae.

Neuronopathy, distal hereditary motor, autosomal dominant 14

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 10

A form of distal hereditary motor neuronopathy, a heterogeneous group of neuromuscular diseases caused by selective degeneration of motor neurons in the anterior horn of the spinal cord, without sensory deficit in the posterior horn. HMND10 is characterized by length-dependent motor neuropathy primarily affecting the lower limbs, and onset of distal muscle weakness and atrophy in early childhood resulting in walking difficulties and gait abnormalities. Some affected individuals have pyramidal signs, including hyperreflexia. More variable features may include mild intellectual disability, minor gyration defects on brain imaging, foot deformities, and connective tissue defects.

Mitochondrial DNA depletion syndrome 1, MNGIE type

A multisystem disease associated with mitochondrial dysfunction. It is clinically characterized by onset between the second and fifth decades of life, ptosis, progressive external ophthalmoplegia, gastrointestinal dysmotility (often pseudoobstruction), diffuse leukoencephalopathy, cachexia, peripheral neuropathy, and myopathy.

Methylmalonic aciduria and homocystinuria, cblC type

An autosomal recessive disorder of cobalamin metabolism characterized by decreased levels of the coenzymes adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl). Affected individuals may have developmental, hematologic, neurologic, metabolic, ophthalmologic, and dermatologic clinical findings. Although considered a disease of infancy or childhood, some individuals develop symptoms in adulthood.

Pyruvate dehydrogenase E3-binding protein deficiency

A metabolic disorder characterized by decreased activity of the pyruvate dehydrogenase complex without observable reduction in the activities of enzymes E1, E2, or E3. Clinical features include hypotonia and psychomotor retardation.

Krabbe disease

An autosomal recessive disorder characterized by insufficient catabolism of several galactolipids that are important for normal myelin production. Four clinical forms are recognized. The infantile form accounts for 90% of cases. It manifests before six months of age with irritability, spasticity, arrest of motor and mental development, and bouts of temperature elevation without infection. This is followed by myoclonic jerks of arms and legs, oposthotonus, hypertonic fits, and mental regression, which progresses to a severe decerebrate condition with no voluntary movements and death from respiratory infections or cerebral hyperpyrexia before 2 years of age. Cases with later onset present with unexplained blindness, weakness and sensorimotor peripheral neuropathy, mental deterioration and death.

Congenital insensitivity to pain with anhidrosis

Characterized by a congenital insensitivity to pain, anhidrosis (absence of sweating), absence of reaction to noxious stimuli, self-mutilating behavior, and intellectual disability. This rare autosomal recessive disorder is also known as congenital sensory neuropathy with anhidrosis or hereditary sensory and autonomic neuropathy type IV or familial dysautonomia type II.

Hemolytic anemia, CD59-mediated, with or without polyneuropathy

An autosomal recessive disorder characterized by infantile onset of chronic hemolysis and a relapsing-remitting polyneuropathy, often exacerbated by infection, and manifested as hypotonia, limb muscle weakness, and hyporeflexia.

Dihydrolipoamide dehydrogenase deficiency

An autosomal recessive metabolic disorder characterized biochemically by a combined deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), pyruvate dehydrogenase complex (PDC), and alpha-ketoglutarate dehydrogenase complex (KGDC). Clinically, affected individuals have lactic acidosis and neurologic deterioration due to sensitivity of the central nervous system to defects in oxidative metabolism.

Pyruvate dehydrogenase E1-alpha deficiency

An enzymatic defect causing primary lactic acidosis in children. It is associated with a broad clinical spectrum ranging from fatal lactic acidosis in the newborn to chronic neurologic dysfunction with structural abnormalities in the central nervous system without systemic acidosis.

Peroxisome biogenesis disorder complementation group 7

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 K

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).

Neuropathy, hereditary sensory and autonomic, 7

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. HSAN7 is characterized by congenital inability to experience pain resulting in self-mutilations, slow-healing wounds, and multiple painless fractures. mild muscle weakness, delayed motor development, slightly reduced motor and sensory nerve conduction velocities, hyperhidrosis and gastrointestinal dysfunction.

Spastic paraplegia 31, 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 12, 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.

Mitochondrial complex IV deficiency, nuclear type 5

An autosomal recessive, severe mitochondrial disease with multisystemic manifestations and early onset. Clinical features include delayed psychomotor development, impaired intellectual development with speech delay, mild dysmorphic facial features, hypotonia, ataxia, and seizures. Brain imaging shows bilaterally symmetrical necrotic lesions in subcortical brain regions. Mortality is high, due to episodes of severe metabolic acidosis and coma.

Lethal congenital contracture syndrome 7

A form of lethal congenital contracture syndrome, an autosomal recessive disorder characterized by degeneration of anterior horn neurons, extreme skeletal muscle atrophy and congenital non-progressive joint contractures. The contractures can involve the upper or lower limbs and/or the vertebral column, leading to various degrees of flexion or extension limitations evident at birth. LCCS7 is a severe axoglial disease characterized by congenital distal joint contractures, polyhydramnios, reduced fetal movements, and motor paralysis leading to death early in the neonatal period.

Spinal muscular atrophy, lower extremity-predominant 2A, childhood onset, autosomal dominant

An autosomal dominant form of spinal muscular atrophy characterized by early-childhood onset of muscle weakness and atrophy predominantly affecting the proximal and distal muscles of the lower extremity, although some patients may show upper extremity involvement. The disorder results in delayed walking, waddling gait, difficulty walking, and loss of distal reflexes. Some patients may have foot deformities or hyperlordosis, and some show mild upper motor signs, such as spasticity. Sensation, bulbar function, and cognitive function are preserved. The disorder shows very slow progression throughout life.

Peroxisome biogenesis disorder 2A

A fatal peroxisome biogenesis disorder belonging to the Zellweger disease spectrum and characterized clinically by severe neurologic dysfunction with profound psychomotor retardation, severe hypotonia and neonatal seizures, craniofacial abnormalities, liver dysfunction, and biochemically by the absence of peroxisomes. Additional features include cardiovascular and skeletal defects, renal cysts, ocular abnormalities, and hearing impairment. Most severely affected individuals with the classic form of the disease (classic Zellweger syndrome) die within the first year of life.

Neuropathy, hereditary motor and sensory, 6B, with optic atrophy

An autosomal recessive neurologic disorder characterized by early-onset optic atrophy, progressive visual loss, and peripheral sensorimotor neuropathy manifesting as axonal Charcot-Marie-Tooth disease, with variable age at onset and severity. Charcot-Marie-Tooth disease is 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. It is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies and primary peripheral axonal neuropathies. Peripheral axonal neuropathies are characterized by signs of axonal regeneration in the absence of obvious myelin alterations, and normal or slightly reduced nerve conduction velocities.

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.

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 1

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.

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).

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.

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).

Sodium-dependent multivitamin transporter deficiency

An autosomal recessive multisystemic metabolic disorder characterized by early infantile onset, progressive neurodegeneration, global developmental delay, and developmental regression with loss of early motor and cognitive milestones. Additional variable features include seizures, ataxia, spasticity, peripheral neuropathy, immune defects, and osteopenia. Treatment with biotin, pantothenic acid, and lipoate may result in clinical improvement.

Niemann-Pick disease A

An early-onset lysosomal storage disorder caused by failure to hydrolyze sphingomyelin to ceramide. It results in the accumulation of sphingomyelin and other metabolically related lipids in reticuloendothelial and other cell types throughout the body, leading to cell death. Niemann-Pick disease type A is a primarily neurodegenerative disorder characterized by onset within the first year of life, intellectual disability, digestive disorders, failure to thrive, major hepatosplenomegaly, and severe neurologic symptoms. The severe neurological disorders and pulmonary infections lead to an early death, often around the age of four. Clinical features are variable. A phenotypic continuum exists between type A (basic neurovisceral) and type B (purely visceral) forms of Niemann-Pick disease, and the intermediate types encompass a cluster of variants combining clinical features of both types A and B.

Neuropathy, hereditary motor and sensory, 6C, with optic atrophy

An autosomal recessive neurologic disorder characterized by childhood onset of axonal, sensorimotor polyneuropathy affecting mainly the lower limbs, and adult-onset optic atrophy. Clinical features include progressive distal muscle weakness and atrophy, significant standing and walking difficulties, areflexia, neurogenic pain and progressive visual 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.