Intellectual developmental disorder, X-linked, syndromic, Billuart type

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRXSBL patients manifest intellectual disability associated with cerebellar hypoplasia and distinctive facial dysmorphism.

Agenesis of the corpus callosum, with facial anomalies and cerebellar ataxia

An autosomal recessive intellectual disability syndrome characterized by congenital microcephaly, low anterior hairline, bitemporal narrowing, low-set protruding ears, strabismus and tented thick eyebrows with sparse hair in their medial segment.

Craniosynostosis 6

A form of craniosynostosis, a primary abnormality of skull growth involving premature fusion of one or more cranial sutures. The growth velocity of the skull often cannot match that of the developing brain resulting in an abnormal head shape and, in some cases, increased intracranial pressure, which must be treated promptly to avoid permanent neurodevelopmental disability.

Joubert syndrome 36

A form of Joubert syndrome, 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. JBTS36 inheritance is autosomal recessive.

Orofaciodigital syndrome 1

A form of orofaciodigital syndrome, a group of heterogeneous disorders characterized by abnormalities in the oral cavity, face, and digits and associated phenotypic abnormalities that lead to the delineation of various subtypes. OFD1 is X-linked dominant syndrome, lethal in males. Craniofacial findings consist of facial asymmetry, hypertelorism, median cleft, or pseudocleft of the upper lip, hypoplasia of the alae nasi, oral clefts and abnormal frenulea, tongue anomalies (clefting, cysts, hamartoma), and anomalous dentition involving missing or extra teeth. Asymmetric brachydactyly and/or syndactyly of the fingers and toes occur frequently. Approximately 50% of OFD1 females have some degree of intellectual disability. Some patients have structural central nervous system anomalies such as agenesis of the corpus callosum, cerebellar agenesis, or a Dandy-Walker malformation. Patients with OFD1 can develop fibrocystic disease of the liver and pancreas, in addition to polycystic kidneys.

Orofaciodigital syndrome 4

A form of orofaciodigital syndrome, a group of heterogeneous disorders characterized by malformations of the oral cavity, face and digits, and associated phenotypic abnormalities that lead to the delineation of various subtypes. OFD4 patients have tongue nodules, multiple frenulae, broad flat nose, hypertelorism, and short rib polydactyly with tibial dysplasia (Majewski syndrome). The presence of severe tibial aplasia differentiates OFD4 from OFD1. Additional features of cystic dysplastic kidneys and brain malformation, including occipital encephalocele, are observed in severely affected patients.

Orofaciodigital syndrome 15

A form of orofaciodigital syndrome, a group of heterogeneous disorders characterized by malformations of the oral cavity, face and digits, and associated phenotypic abnormalities that lead to the delineation of various subtypes. OFD15 features include facial dysmorphism, lobulated tongue, clefting of the alveolar ridges, left hand postaxial polydactyly, broad right hallux and left hallux duplication, and intermittent respiratory difficulty. Brain anomalies include vermis hypoplasia with molar tooth sign, agenesis of corpus callosum, and ventricular dilation. OFD15 inheritance is autosomal recessive.

Neurodegeneration, childhood-onset, with cerebellar atrophy

An autosomal recessive disorder characterized by early onset of progressive neurodegeneration affecting the central and peripheral nervous systems. Clinical features include global developmental delay, impaired intellectual development, poor or absent speech, and motor abnormalities. Brain imaging shows cerebellar atrophy. Death in childhood may occur.

Thyroid cancer, non-medullary, 2

A form of non-medullary thyroid cancer (NMTC), a cancer characterized by tumors originating from the thyroid follicular cells. NMTCs represent approximately 95% of all cases of thyroid cancer and are classified into papillary, follicular, Hurthle cell, and anaplastic neoplasms.

Congenital disorder of glycosylation 2N

A form of congenital disorder of glycosylation, a genetically heterogeneous group of autosomal recessive, multisystem disorders caused by a defect in glycoprotein biosynthesis and characterized by under-glycosylated serum glycoproteins. Congenital disorders of glycosylation result in a wide variety of clinical features, such as defects in the nervous system development, psychomotor retardation, dysmorphic features, hypotonia, coagulation disorders, and immunodeficiency. The broad spectrum of features reflects the critical role of N-glycoproteins during embryonic development, differentiation, and maintenance of cell functions.

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.

Lissencephaly 3

A classic type lissencephaly associated with psychomotor retardation and seizures. Features include agyria or pachygyria or laminar heterotopia, severe intellectual disability, motor delay, variable presence of seizures, and abnormalities of corpus callosum, hippocampus, cerebellar vermis and brainstem.

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.

Cerebellar atrophy, visual impairment, and psychomotor retardation

An autosomal recessive, neurodegenerative disorder characterized by developmental delay, intellectual disability, hypotonia, scoliosis, cerebellar atrophy, and variable dysmorphic features.

Congenital disorder of glycosylation 2M

An X-linked dominant, severe neurologic disorder characterized by developmental delay, hypotonia, ocular anomalies, and brain malformations. Othere more variable clinical features included seizures, hypsarrhythmia, poor feeding, microcephaly, recurrent infections, dysmorphic features, shortened limbs, and coagulation defects. Congenital disorders of glycosylation are caused by a defect in glycoprotein biosynthesis and characterized by under-glycosylated serum glycoproteins and a wide variety of clinical features. The broad spectrum of features reflects the critical role of N-glycoproteins during embryonic development, differentiation, and maintenance of cell functions.

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.

Pontocerebellar hypoplasia 9

A form of pontocerebellar hypoplasia, a disorder characterized by structural defects of the pons and cerebellum, evident upon brain imaging. PCH9 features include severely delayed psychomotor development, progressive microcephaly, spasticity, seizures, and brain abnormalities, including brain atrophy, thin corpus callosum, and delayed myelination.

Autism, X-linked 5

A complex multifactorial, pervasive developmental disorder characterized by impairments in reciprocal social interaction and communication, restricted and stereotyped patterns of interests and activities, and the presence of developmental abnormalities by 3 years of age. Most individuals with autism also manifest moderate intellectual disability.

Neural tube defects

Congenital malformations of the central nervous system and adjacent structures related to defective neural tube closure during the first trimester of pregnancy. Failure of neural tube closure can occur at any level of the embryonic axis. Common NTD forms include anencephaly, myelomeningocele and spina bifida, which result from the failure of fusion in the cranial and spinal region of the neural tube. NTDs have a multifactorial etiology encompassing both genetic and environmental components.

Poretti-Boltshauser syndrome

An autosomal recessive disorder characterized by cerebellar dysplasia, cerebellar vermis atrophy, cerebellar cysts in most patients, high myopia, variable retinal dystrophy, and eye movement abnormalities including strabismus, ocular apraxia, nystagmus. Affected individuals have ataxia, delayed motor development, language impairment, and intellectual disability with variable severity.

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.

Congenital disorder of glycosylation 2D

A multisystem disorder caused by a defect in glycoprotein biosynthesis and characterized by under-glycosylated serum glycoproteins. Congenital disorders of glycosylation result in a wide variety of clinical features, such as defects in the nervous system development, psychomotor retardation, dysmorphic features, hypotonia, coagulation disorders, and immunodeficiency. The broad spectrum of features reflects the critical role of N-glycoproteins during embryonic development, differentiation, and maintenance of cell functions.

Neural tube defects

Congenital malformations of the central nervous system and adjacent structures related to defective neural tube closure during the first trimester of pregnancy. Failure of neural tube closure can occur at any level of the embryonic axis. Common NTD forms include anencephaly, myelomeningocele and spina bifida, which result from the failure of fusion in the cranial and spinal region of the neural tube. NTDs have a multifactorial etiology encompassing both genetic and environmental components.

Pontocerebellar hypoplasia 7

A form of pontocerebellar hypoplasia, a group of related disorders characterized by underdevelopment of the pons and the cerebellum. Pontocerebellar hypoplasia also causes impaired growth of other parts of the brain, leading to an unusually small head size. PCH7 patients manifest delayed psychomotor development, hypotonia, breathing abnormalities, and gonadal abnormalities.

Pancreatic and cerebellar agenesis

A disease characterized by neonatal diabetes mellitus, cerebellar agenesis or hypoplasia, severe intrauterine growth retardation, the presence of very little subcutaneous fat, and dysmorphic facial features.

Neurodegeneration, childhood-onset, with brain atrophy

An autosomal dominant neurodegenerative disease with onset in childhood, characterized by progressive cortical atrophy, developmental delay, developmental regression, loss of motor skills and ambulation, absence of language, and intellectual disability.

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.

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.

Pontocerebellar hypoplasia 2F

A neurodevelopmental disorder characterized by progressive microcephaly, cognitive and motor delay, poor or absent speech, seizures, and spasticity. PCH2F inheritance is autosomal recessive.

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.

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.

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.

Parietal foramina 2

Autosomal dominant disease characterized by oval defects of the parietal bones caused by deficient ossification around the parietal notch, which is normally obliterated during the fifth fetal month. PFM2 is also a clinical feature of Potocki-Shaffer syndrome.

Joubert syndrome 17

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 3

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 3 shows minimal extra central nervous system involvement and appears not to be associated with renal dysfunction.

Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome 1

A syndrome characterized by megalencephaly, hydrocephalus, and polymicrogyria; polydactyly may also be seen. There is considerable phenotypic similarity between this disorder and the megalencephaly-capillary malformation syndrome.

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.

Pontocerebellar hypoplasia 3

A form of pontocerebellar hypoplasia, a disorder characterized by structural defects of the pons and cerebellum. Brain MRI shows an abnormally small cerebellum and brainstem, decreased cerebral white matter, and a thin corpus callosum. PCH3 features include seizures, short stature, optic atrophy, progressive microcephaly, severe developmental delay.

Pontocerebellar hypoplasia 2B

A disorder characterized by an abnormally small cerebellum and brainstem, and progressive microcephaly from birth combined with extrapyramidal dyskinesia. Severe chorea occurs and epilepsy is frequent. There are no signs of spinal cord anterior horn cells degeneration.

Cerebral arteriopathy, autosomal dominant, with subcortical infarcts and leukoencephalopathy, 1

A cerebrovascular disease characterized by multiple subcortical infarcts, pseudobulbar palsy, dementia, and the presence of granular deposits in small cerebral arteries producing ischemic stroke.

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.

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.

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.

Tuberous sclerosis 1

An autosomal dominant multi-system disorder that affects especially the brain, kidneys, heart, and skin. It is characterized by hamartomas (benign overgrowths predominantly of a cell or tissue type that occurs normally in the organ) and hamartias (developmental abnormalities of tissue combination). Clinical manifestations include epilepsy, learning difficulties, behavioral problems, and skin lesions. Seizures can be intractable and premature death can occur from a variety of disease-associated causes.

Ritscher-Schinzel syndrome 2

A form of Ritscher-Schinzel syndrome, a developmental malformation syndrome characterized by cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. RTSC2 is an X-linked recessive form characterized by intellectual disability associated with posterior fossa defects, cardiac malformations, and minor abnormalities of the face and distal extremities.

Pontocerebellar hypoplasia 13

A form of pontocerebellar hypoplasia, a disorder characterized by structural defects of the pons and cerebellum, evident upon brain imaging. PCH13 is an autosomal recessive form characterized by delayed psychomotor development, absent speech, severe intellectual disability and postnatal microcephaly, with brain malformations consisting of cerebellar atrophy and hypoplastic corpus callosum. Additional features, including seizures and visual impairment, are variable.

Pontocerebellar hypoplasia 2D

A disorder characterized by postnatal onset of progressive atrophy of the cerebrum and cerebellum, microcephaly, profound intellectual disability, spasticity, and variable seizures.

Parietal foramina 1

Autosomal dominant disease characterized by oval defects of the parietal bones caused by deficient ossification around the parietal notch, which is normally obliterated during the fifth fetal month.

Nephronophthisis 3

An autosomal recessive disorder resulting in end-stage renal disease. It is characterized by polyuria, polydipsia, anemia. Onset of terminal renal failure occurr significantly later (median age, 19 years) than in juvenile nephronophthisis. Renal pathology is characterized by alterations of tubular basement membranes, tubular atrophy and dilation, sclerosing tubulointerstitial nephropathy, and renal cyst development predominantly at the corticomedullary junction.

Ritscher-Schinzel syndrome 4

An autosomal dominant form of Ritscher-Schinzel syndrome, a developmental malformation syndrome characterized by cerebellar brain anomalies associated with global developmental delay and impaired intellectual development, congenital heart defects, and craniofacial abnormalities.

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.

Cerebellar dysfunction, impaired intellectual development, and hypogonadotropic hypogonadism

An autosomal recessive disorder characterized by delayed motor development, ataxia with cerebellar hypoplasia, severe progressive scoliosis, moderate to severe intellectual disability, and delayed puberty with congenital hypogonadotropic hypogonadism.

Pettigrew syndrome

An X-linked syndrome characterized by intellectual disability and additional highly variable features, including choreoathetosis, hydrocephalus, Dandy-Walker malformation, seizures, and iron or calcium deposition in the brain. Intellectual disability is characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period.

Smith-Kingsmore syndrome

An autosomal dominant syndrome characterized by intellectual disability, macrocephaly, seizures, umbilical hernia, and facial dysmorphic features.

You-Hoover-Fong syndrome

A syndrome characterized by severe global developmental delay, intellectual disability, dysmorphic facial features, microcephaly, abnormal movements, congenital heart disease comprising developmental abnormalities of the great vessels, and abnormal auditory and visual function. The transmission pattern is consistent with autosomal recessive inheritance.

Pontocerebellar hypoplasia 2E

An autosomal recessive neurodegenerative disorder characterized by progressive cerebello-cerebral atrophy, profound intellectual disability, progressive microcephaly, spasticity, and early-onset epilepsy.

Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome 3

A syndrome characterized by megalencephaly, ventriculomegaly that may lead to hydrocephalus, and polymicrogyria; polydactyly may also be seen. There is considerable phenotypic similarity between this disorder and the megalencephaly-capillary malformation syndrome.

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.

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.

Ritscher-Schinzel syndrome 3

A form of Ritscher-Schinzel syndrome, a developmental malformation syndrome characterized by cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. RTSC3 is an autosomal recessive form. Affected individuals show cranio-cerebello-cardiac anomalies, coloboma, microphthalmia, chondrodysplasia punctata, complicated skeletal malformations, periventricular nodular heterotopia and proteinuria.

Spastic paraplegia 8, 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.

Pontocerebellar hypoplasia 8

An autosomal recessive neurodevelopmental disorder characterized by severe psychomotor retardation, abnormal movements, hypotonia, spasticity, and variable visual defects. Brain MRI shows pontocerebellar hypoplasia, decreased cerebral white matter, and a thin corpus callosum.

Pontocerebellar hypoplasia 6

A disorder characterized by an abnormally small cerebellum and brainstem, infantile encephalopathy, generalized hypotonia, lethargy and poor feeding. Recurrent apnea, intractable seizures occur early in the course of this condition.

Pontocerebellar hypoplasia 10

A form of pontocerebellar hypoplasia, a disorder characterized by structural defects of the pons and cerebellum, evident upon brain imaging. PCH10 features include cortical dysgenesis marked by a simplified gyral pattern, cortical atrophy, mild or focal cerebellar vermian volume loss, delayed myelination, progressive microcephaly, global growth and developmental delays, severe intellectual disabilities, and seizures refractory to treatment.

Pontocerebellar hypoplasia 4

A disorder characterized by an abnormally small cerebellum and brainstem, severe neonatal encephalopathy, microcephaly, myoclonus and muscular hypertonia. There is a severe inferior olivary and pontine neuronal loss and a diffuse white matter gliosis.

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.