Spinocerebellar ataxia, autosomal recessive, 21

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. SCAR21 is characterized by cerebellar atrophy and ataxia with onset in early childhood. Patients also manifest recurrent episodes of liver failure, hepatic fibrosis and a peripheral neuropathy.

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.

Spinocerebellar ataxia 23

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. SCA23 is an adult-onset autosomal dominant form characterized by slowly progressive gait and limb ataxia, with variable additional features, including peripheral neuropathy and dysarthria.

Spinocerebellar ataxia 2

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. SCA2 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. SCA2 is characterized by hyporeflexia, myoclonus and action tremor and dopamine-responsive parkinsonism. In some patients, SCA2 presents as pure familial parkinsonism without cerebellar signs.

Spastic paraplegia 39, 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. SPG39 is associated with a motor axonopathy affecting upper and lower limbs and resulting in progressive wasting of distal upper and lower extremity muscles.

Cortical dysplasia, complex, with other brain malformations 7

A malformation of the cortex in which the brain surface is irregular and characterized by an excessive number of small gyri with abnormal lamination. Polymicrogyria is a heterogeneous disorder, considered to be the result of postmigratory abnormal cortical organization.

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).

Joubert syndrome 20

A disorder presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay. 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 retinal dystrophy and renal disease.

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.

Spinocerebellar ataxia, autosomal recessive, 28

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. SCAR28 patients manifest mild motor developmental delay, gait ataxia, and dysarthria. Some patients show mildly impaired intellectual development. Disease onset is in early childhood.

Spinocerebellar ataxia 27A

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. SCA27A is an autosomal dominant, slowly progressive form characterized by gait disturbances, ataxia with tremor, dysarthria, orofacial dyskinesia, gaze-evoked nystagmus, and learning disabilities. There is significant variability, and patients show various combinations of neurologic features.

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.

Spinocerebellar ataxia 19

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. SCA19 is a relatively mild, cerebellar ataxic syndrome with cognitive impairment, pyramidal tract involvement, tremor and peripheral neuropathy, and mild atrophy of the cerebellar hemispheres and vermis.

Spinocerebellar ataxia, autosomal recessive, 10

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. SCAR10 is characterized by onset in the teenage or young adult years of gait and limb ataxia, dysarthria, and nystagmus associated with marked cerebellar atrophy on brain imaging.

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.

Fragile X syndrome

An X-linked dominant disease characterized by moderate to severe intellectual disability, macroorchidism (enlargement of the testicles), large ears, prominent jaw, and high-pitched, jocular speech. The defect in most patients results from an amplification of a CGG repeat region in the FMR1 gene and abnormal methylation.

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.

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.

Meckel syndrome 6

A disorder characterized by a combination of renal cysts and variably associated features including developmental anomalies of the central nervous system (typically encephalocele), hepatic ductal dysplasia and cysts, and polydactyly.

Spinocerebellar ataxia 13

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. SCA13 is an autosomal dominant cerebellar ataxia (ADCA) characterized by slow progression and variable age at onset, ranging from childhood to late adulthood. Intellectual disability can be present in some patients.

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.

Spinocerebellar ataxia, autosomal recessive, 30

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 a progressive disease characterized by childhood-onset global developmental delay with variably impaired intellectual development, motor dysfunction, and cerebellar ataxia. Affected individuals may also have psychiatric abnormalities.

Spinocerebellar ataxia 42

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. SCA42 is a slowly progressive, autosomal dominant form with variable severity.

Ataxia, intention tremor, and hypotonia syndrome, childhood-onset

An autosomal dominant neurodevelopmental disorder characterized by global developmental delay, mildly impaired intellectual development with speech delay or learning disabilities, delayed walking due to ataxia, intention tremor, and hypotonia apparent from early childhood. Brain imaging shows cerebellar atrophy in some patients.

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.

Spastic ataxia 3, autosomal recessive

A neurologic disorder characterized by cerebellar ataxia, ataxic gait, spasticity, and hyperreflexia. Other variable features include dysarthria, dysmetria, mild cognitive impairment, urinary urgency and dystonic positioning.

Spastic ataxia 8, autosomal recessive, with hypomyelinating leukodystrophy

An autosomal recessive neurodegenerative disorder characterized by early-onset hypotonia which progresses to a pyramidal syndrome with ataxia, spasticity, hyperreflexia, weakness and loss of ambulation. Brain imaging shows cerebellar atrophy and hypomyelinating leukodystrophy.

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.

Spinocerebellar ataxia, autosomal recessive, 18

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. SCAR18 features include progressive cerebellar atrophy, delayed psychomotor development, severely impaired gait, ocular movement abnormalities, and intellectual disability.

Spinocerebellar ataxia 12

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. SCA12 is an autosomal dominant cerebellar ataxia (ADCA).

Ataxia-pancytopenia syndrome

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

Joubert syndrome 2

A disorder presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay. 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 retinal dystrophy and renal disease.

Lichtenstein-Knorr syndrome

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

Spinocerebellar ataxia, autosomal recessive, 2

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. SCAR2 is characterized by onset of impaired motor development and ataxic gait in early childhood. Additional features often include loss of fine motor skills, dysarthria, nystagmus, cerebellar signs, and delayed cognitive development with intellectual disability.

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.

Joubert syndrome 5

A disorder presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay. 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 retinal dystrophy and renal disease. Joubert syndrome type 5 shares the neurologic and neuroradiologic features of Joubert syndrome together with severe retinal dystrophy and/or progressive renal failure characterized by nephronophthisis.

Stargardt disease 3

A form of Stargardt disease, a common hereditary macular degeneration characterized by decreased central vision, atrophy of the macula and underlying retinal pigment epithelium, and frequent presence of prominent flecks in the posterior pole of the retina. STGD3 is an autosomal dominant form with onset most commonly in the second decade of life.

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.

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).

Charcot-Marie-Tooth disease, X-linked dominant, 1

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. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies characterized by severely reduced motor nerve conduction velocities (NCVs) (less than 38m/s) and segmental demyelination and remyelination, and primary peripheral axonal neuropathies characterized by normal or mildly reduced NCVs and chronic axonal degeneration and regeneration on nerve biopsy. CMTX1 has both demyelinating and axonal features. Central nervous system involvement may occur.

Spastic paraplegia 7, 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. SPG7 is a complex form. Additional clinical features are cerebellar syndrome, supranuclear palsy, and cognitive impairment, particularly disturbance of attention and executive functions.

Combined oxidative phosphorylation deficiency 13

A mitochondrial disorder characterized by early onset severe encephalomyopathy, dystonia, choreoathetosis, bucofacial dyskinesias and combined mitochondrial respiratory chain deficiency. Nerve conductions velocities are decreased. Levels of plasma and cerebrospinal fluid lactate are increased.

Spinocerebellar ataxia, autosomal recessive, 34

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. SCAR34 is characterized by congenital cerebellar ataxia associated with dysarthia, quadrupedal gait and intellectual disability.

Joubert syndrome 21

A disorder presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay. 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 retinal dystrophy, renal disease, liver fibrosis, and polydactyly.

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.

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.

Spinocerebellar ataxia, autosomal recessive, 20

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. SCAR20 is characterized by cerebellar atrophy, ataxia, coarsened facial features, severely delayed psychomotor development with poor or absent speech, and intellectual disability.

Spinocerebellar ataxia 31

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. SCA31 belongs to the autosomal dominant cerebellar ataxias type III (ADCA III) which are characterized by pure cerebellar ataxia without additional signs.

Ceroid lipofuscinosis, neuronal, 2

A form of neuronal ceroid lipofuscinosis. Neuronal ceroid lipofuscinoses are progressive neurodegenerative, lysosomal storage diseases characterized by intracellular accumulation of autofluorescent liposomal material, and clinically by seizures, dementia, visual loss, and/or cerebral atrophy. The lipopigment pattern seen most often in CLN2 consists of curvilinear profiles.

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.

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.

Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 3

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. SCAN3 is an autosomal recessive disorder characterized by onset in the first decade of slowly progressive distal muscle weakness and atrophy and distal sensory impairment due to an axonal peripheral neuropathy. Affected individuals have gait disturbances and sometimes manual dexterity difficulties, as well as cerebellar ataxia associated with cerebellar atrophy on brain imaging.

Spinocerebellar ataxia 50

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. SCA50 is an autosomal dominant form characterized by cerebellar ataxia, oculomotor apraxia and other eye movement abnormalities, and cerebellar atrophy on brain imaging.

Cerebellar ataxia, impaired intellectual development, and dysequilibrium syndrome 4

An autosomal recessive, congenital cerebellar ataxia associated with dysarthia, quadrupedal gait and intellectual disability.

Spinocerebellar ataxia 6

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. SCA6 is an autosomal dominant cerebellar ataxia (ADCA), mainly caused by expansion of a CAG repeat in the coding region of CACNA1A. There seems to be a correlation between the repeat number and earlier onset of the disorder.

Riddle syndrome

An autosomal recessive disorder characterized by increased radiosensitivity, immunodeficiency, mild motor control and learning difficulties, facial dysmorphism, and short stature.

Spastic ataxia 2, autosomal recessive

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

Spinocerebellar ataxia 5

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. SCA5 is an autosomal dominant cerebellar ataxia (ADCA). It is a slowly progressive disorder with variable age at onset, ranging between 10 and 50 years.

Neurodevelopmental disorder with motor abnormalities, seizures, and facial dysmorphism

An autosomal dominant disorder characterized by global developmental delay, impaired intellectual development, early-onset seizures, poor overall growth, delayed walking, hypotonia and/or ataxia, and facial dysmorphism. Some patients have hypoplasia of the corpus callosum and cerebral atrophy.

Spinocerebellar ataxia 1

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. SCA1 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. SCA1 is caused by expansion of a CAG repeat in the coding region of ATXN1. Longer expansions result in earlier onset and more severe clinical manifestations of the disease.

Anemia, sideroblastic, 3, pyridoxine-refractory

A form of sideroblastic anemia, a bone marrow disorder defined by the presence of pathologic iron deposits in erythroblast mitochondria. Sideroblastic anemia is characterized by anemia of varying severity, hypochromic peripheral erythrocytes, systemic iron overload secondary to chronic ineffective erythropoiesis, and the presence of bone marrow ringed sideroblasts. Sideroblasts are characterized by iron-loaded mitochondria clustered around the nucleus. SIDBA3 is refractory to treatment with vitamin B6, while iron chelation therapy may result in clinical improvement. SIDBA3 inheritance is autosomal recessive.

Dystonia 12

An autosomal dominant dystonia-parkinsonism disorder. Dystonia is defined by the presence of sustained involuntary muscle contractions, often leading to abnormal postures. DYT12 patients develop dystonia and parkinsonism between 15 and 45 years of age. The disease is characterized by an unusually rapid evolution of signs and symptoms. The sudden onset of symptoms over hours to a few weeks, often associated with physical or emotional stress, suggests a trigger initiating a nervous system insult resulting in permanent neurologic disability.

Spinocerebellar ataxia, autosomal recessive, 15

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. SCAR15 patients manifest cerebellar ataxia in early childhood and delayed motor development with delayed walking. Additional features include dysarthria, upper limb involvement, abnormal eye movements, and hyporeflexia.

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.

Joubert syndrome 15

An autosomal recessive disorder presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay. 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 retinal dystrophy, renal disease, liver fibrosis and polydactyly.

Meckel syndrome 1

A disorder characterized by a combination of renal cysts and variably associated features including developmental anomalies of the central nervous system (typically encephalocele), hepatic ductal dysplasia and cysts, and polydactyly.

Neuropathy, hereditary sensory, 1E

A neurodegenerative disorder characterized by adult onset of progressive peripheral sensory loss associated with progressive hearing impairment and early-onset dementia.

Cerebellar dysfunction with variable cognitive and behavioral abnormalities

An autosomal dominant neurodevelopmental disorder characterized by mildly delayed psychomotor development, early onset of cerebellar ataxia, and intellectual disability later in childhood and adult life. Other features may include neonatal hypotonia, dysarthria, and dysmetria. Brain imaging in some patients shows cerebellar atrophy. Dysmorphic facial features are variable.

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.

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.

Joubert syndrome 16

An autosomal recessive disorder characterized by oculomotor apraxia, variable coloboma, and rare kidney involvement. Neuroradiologically, it is characterized by an abnormally large interpeduncular fossa, giving the appearance of a molar tooth on transaxial slices (molar tooth sign). Additional variable features include retinal dystrophy and polydactyly.

Hypoparathyroidism-retardation-dysmorphism syndrome

An autosomal recessive multisystem disorder characterized by hypoparathyroidism, intrauterine and postnatal growth retardation, psychomotor retardation, epilepsy, microcephaly, and facial dysmorphism.

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.

Congenital cataracts, facial dysmorphism, and neuropathy

An autosomal recessive developmental disorder characterized by a complex clinical phenotype with seemingly unrelated features involving multiple organs and systems. Developmental abnormalities include congenital cataracts and microcorneae, hypomyelination of the peripheral nervous system, impaired physical growth, delayed early motor and intellectual development, facial dysmorphism and hypogonadism. Central nervous system involvement, with cerebral and spinal cord atrophy, may be the result of disrupted development with superimposed degenerative changes. Affected individuals are prone to severe rhabdomyolysis after viral infections and to serious complications related to general anesthesia (such as pulmonary edema and epileptic seizures).

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.