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.

Microcephaly, Amish type

A disorder characterized by severe congenital microcephaly and severe 2-ketoglutaric aciduria leading to death within the first year.

Glycogen storage disease 1A

A metabolic disorder characterized by impairment of terminal steps of glycogenolysis and gluconeogenesis. Patients manifest a wide range of clinical symptoms and biochemical abnormalities, including hypoglycemia, severe hepatomegaly due to excessive accumulation of glycogen, kidney enlargement, growth retardation, lactic acidemia, hyperlipidemia, and hyperuricemia.

GM1-gangliosidosis 1

An autosomal recessive lysosomal storage disease marked by the accumulation of GM1 gangliosides, glycoproteins and keratan sulfate primarily in neurons of the central nervous system. GM1-gangliosidosis type 1 is characterized by onset within the first three months of life, central nervous system degeneration, coarse facial features, hepatosplenomegaly, skeletal dysmorphology reminiscent of Hurler syndrome, and rapidly progressive psychomotor deterioration. Urinary oligosaccharide levels are high. It leads to death usually between the first and second year of life.

Hyperlysinemia, 1

An autosomal recessive metabolic condition with variable clinical features. Some patients present with non-specific seizures, hypotonia, or mildly delayed psychomotor development, and increased serum lysine and pipecolic acid on laboratory analysis. However, about half of the probands are reported to be asymptomatic, and hyperlysinemia is generally considered to be a benign metabolic variant.

Mitochondrial DNA depletion syndrome 3

A disorder due to mitochondrial dysfunction characterized by onset in infancy of progressive liver failure, hypoglycemia, increased lactate in body fluids, and neurologic abnormalities including hypotonia, encephalopathy, peripheral neuropathy. Affected tissues show both decreased activity of the mtDNA-encoded respiratory chain complexes and mtDNA depletion.

Albinism, oculocutaneous, 6

A disorder characterized by a reduction or complete loss of melanin in the skin, hair and eyes. Patients show reduced or lacking pigmentation often accompanied by eye symptoms such as photophobia, strabismus, moderate to severe visual impairment, and nystagmus.

Hemochromatosis 2B

A juvenile form of hemochromatosis, a disorder of iron metabolism with excess deposition of iron in a variety of organs leading to their failure, bronze skin pigmentation, hepatic cirrhosis, arthropathy and diabetes. The most common symptoms of juvenile hemochromatosis at presentation are hypogonadism and cardiomyopathy.

Citrin deficiency, adolescent or adult onset

An autosomal recessive metabolic disorder characterized by elevated serum and urine citrulline levels, ammonia intoxication, and neuropsychiatric symptoms including abnormal behaviors, loss of memory, seizures and coma. Death can result from brain edema.

Pontocerebellar hypoplasia 1A

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

Pontocerebellar hypoplasia 1B

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

Pontocerebellar hypoplasia 1C

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

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.

Hyperprolinemia 1

An inborn error of proline metabolism resulting in elevated levels of proline in the plasma and urine. The disorder is generally benign and most affected individuals are clinically asymptomatic. Some patients, however, have neurologic manifestations, including epilepsy and intellectual disability. Association with certain forms of schizophrenia have been reported.

L-2-hydroxyglutaric aciduria

A rare autosomal recessive disorder clinically characterized by mild psychomotor delay in the first years of life, followed by progressive cerebellar ataxia, dysarthria and moderate to severe intellectual disability. Diagnosis is based on the presence of an excess of L-2-hydroxyglutaric acid in urine, blood and cerebrospinal fluid.

Xanthinuria 2

A disorder characterized by excretion of very large amounts of xanthine in the urine and a tendency to form xanthine stones. Uric acid is strikingly diminished in serum and urine. In addition, XAN2 patients cannot metabolize allopurinol into oxypurinol due to dual deficiency of xanthine dehydrogenase and aldehyde oxidase.

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.

Polyglucosan body myopathy 1 with or without immunodeficiency

A disease characterized by polyglucosan storage myopathy associated with early-onset progressive muscle weakness and progressive dilated cardiomyopathy, which may necessitate cardiac transplant in severe cases. Some patients present with severe immunodeficiency, invasive bacterial infections and chronic autoinflammation.

Mucopolysaccharidosis-plus syndrome

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPSPS is an autosomal recessive form characterized by coarse facial features, dysostosis multiplex, hepatosplenomegaly, respiratory difficulties, intellectual disability, developmental delay, pyramidal signs, severe chronic anemia, renal involvement and cardiac defects. Laboratory analyses show proteinuria with glomerular foamy cells, excess secretion of urinary glycosaminoglycans, and extremely high levels of plasma heparan sulphate. Disease onset is in infancy. Most patients die in the first years of life due to cardiorespiratory failure.

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.

Glutaric aciduria 3

An autosomal recessive metabolic condition characterized by urinary excretion of abnormal quantities of glutaric acid, in the presence of normal 3-hydroxyglutarate, glutarylcarnitine and glutarylglycine urinary levels. Affected individuals show no consistent clinical phenotype and many are asymptomatic.

Hydroxykynureninuria

An inborn error of amino acid metabolism characterized by massive urinary excretion of large amounts of kynurenine, 3-hydroxykynurenine and xanthurenic acid. Affected individuals manifest renal tubular dysfunction, metabolic acidosis, psychomotor retardation, non-progressive encephalopathy, and muscular hypertonia.

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

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.

Mucopolysaccharidosis 1H

A severe form of mucopolysaccharidosis type 1, a rare lysosomal storage disease characterized by progressive physical deterioration with urinary excretion of dermatan sulfate and heparan sulfate. Patients with MPS1H usually present, within the first year of life, a combination of hepatosplenomegaly, skeletal deformities, corneal clouding and severe intellectual disability. Obstructive airways disease, respiratory infection and cardiac complications usually result in death before 10 years of age.

Hypophosphatasia

A metabolic bone disease characterized by defective skeletal mineralization and biochemically by deficient activity of the tissue non-specific isoenzyme of alkaline phosphatase. Four forms are distinguished, depending on the age of onset: perinatal, infantile, childhood and adult type. The perinatal form is the most severe and is almost always fatal. The adult form is mild and characterized by recurrent fractures, osteomalacia, rickets, and loss of teeth. Some cases are asymptomatic, while some patients manifest dental features without skeletal manifestations (odontohypophosphatasia).

Leucine-induced hypoglycemia

Rare cause of hypoglycemia and is described as a condition in which symptomatic hypoglycemia is provoked by high protein feedings. Hypoglycemia is also elicited by administration of oral or intravenous infusions of a single amino acid, leucine.

Acne inversa, familial, 2, with or without Dowling-Degos disease

An autosomal dominant form of acne inversa, a chronic relapsing inflammatory disease of the hair follicles characterized by recurrent draining sinuses, painful skin abscesses, and disfiguring scars. Manifestations typically appear after puberty. Some ACNINV2 patients also exhibit reticulate hyperpigmentation consistent with Dowling-Degos disease.

Congenital disorder of glycosylation 2O

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. CDG2O is characterized by hepatosplenomegaly, liver failure, hypotonia, and psychomotor disability.

Cutis laxa, autosomal recessive, 3A

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

Combined oxidative phosphorylation deficiency 40

An autosomal recessive mitochondrial disorder characterized by prenatal or infantile onset, fetal hydrops, severe hypertrophic cardiomyopathy, poor growth, sensorineural hearing loss, hepatic dysfunction, lactic acidosis, and decreased activities of mitochondrial respiratory complexes I, III, IV, and V. The disorder is lethal, with death occurring in infancy.

Combined oxidative phosphorylation deficiency 9

A mitochondrial disease characterized by failure to thrive, poor feeding, hypertrophic cardiomyopathy, hepatomegaly, and psychomotor retardation. Death in infancy has been observed in some cases.

Combined oxidative phosphorylation deficiency 8

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

GABA-transaminase deficiency

An enzymatic deficiency resulting in psychomotor retardation, hypotonia, hyperreflexia, lethargy, refractory seizures, and EEG abnormalities. GABATD inheritance is autosomal recessive.

3-methylcrotonoyl-CoA carboxylase 1 deficiency

An autosomal recessive disorder of leucine catabolism. The phenotype is variable, ranging from neonatal onset with severe neurological involvement to asymptomatic adults. There is a characteristic organic aciduria with massive excretion of 3-hydroxyisovaleric acid and 3-methylcrotonylglycine, usually in combination with a severe secondary carnitine deficiency.

GM2-gangliosidosis AB

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

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.

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 4

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.

Hyperproinsulinemia

An autosomal dominant condition characterized by elevated levels of serum proinsulin-like material.

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.

Mucopolysaccharidosis 2

An X-linked lysosomal storage disease characterized by intracellular accumulation of heparan sulfate and dermatan sulfate and their excretion in urine. Most children with MPS2 have a severe form with early somatic abnormalities including skeletal deformities, hepatosplenomegaly, and progressive cardiopulmonary deterioration. A prominent feature is neurological damage that presents as developmental delay and hyperactivity but progresses to intellectual disability and dementia. They die before 15 years of age, usually as a result of obstructive airway disease or cardiac failure. In contrast, those with a mild form of MPS2 may survive into adulthood, with attenuated somatic complications and often without intellectual disability.

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).

Paget disease of bone 3

A disorder of bone remodeling characterized by increased bone turnover affecting one or more sites throughout the skeleton, primarily the axial skeleton. Osteoclastic overactivity followed by compensatory osteoblastic activity leads to a structurally disorganized mosaic of bone (woven bone), which is mechanically weaker, larger, less compact, more vascular, and more susceptible to fracture than normal adult lamellar bone.

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.

Niemann-Pick disease C1

A lysosomal storage disorder that affects the viscera and the central nervous system. It is due to defective intracellular processing and transport of low-density lipoprotein derived cholesterol. It causes accumulation of cholesterol in lysosomes, with delayed induction of cholesterol homeostatic reactions. Niemann-Pick disease type C1 has a highly variable clinical phenotype. Clinical features include variable hepatosplenomegaly and severe progressive neurological dysfunction such as ataxia, dystonia and dementia. The age of onset can vary from infancy to late adulthood. An allelic variant of Niemann-Pick disease type C1 is found in people with Nova Scotia ancestry. Patients with the Nova Scotian clinical variant are less severely affected.

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.

Neurodegeneration with brain iron accumulation 6

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

Hyperferritinemia with or without cataract

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

Phosphoglycerate dehydrogenase deficiency

An autosomal recessive inborn error of L-serine biosynthesis, clinically characterized by congenital microcephaly, psychomotor retardation, and seizures.

Muscular dystrophy-dystroglycanopathy limb-girdle C9

An autosomal recessive muscular dystrophy showing onset in early childhood, and associated with intellectual disability without structural brain anomalies.

Glycogen storage disease 9D

A metabolic disorder characterized by slowly progressive, predominantly distal muscle weakness and atrophy. Clinical features include exercise intolerance with early fatigability, pain, cramps and occasionally myoglobinuria.

Multiple sulfatase deficiency

A clinically and biochemically heterogeneous disorder caused by the simultaneous impairment of all sulfatases, due to defective post-translational modification and activation. It combines features of individual sulfatase deficiencies such as metachromatic leukodystrophy, mucopolysaccharidosis, chondrodysplasia punctata, hydrocephalus, ichthyosis, neurologic deterioration and developmental delay.

Multiple congenital anomalies-hypotonia-seizures syndrome 3

An autosomal recessive syndrome characterized by distinct facial features, intellectual disability, hypotonia and seizures, in combination with abnormal skeletal, endocrine, and ophthalmologic findings including impaired vision, as well as abnormal motility of the eyes.

Mucopolysaccharidosis 3C

A form of mucopolysaccharidosis type 3, an autosomal recessive lysosomal storage disease due to impaired degradation of heparan sulfate. MPS3 is characterized by severe central nervous system degeneration, but only mild somatic disease. Onset of clinical features usually occurs between 2 and 6 years; severe neurologic degeneration occurs in most patients between 6 and 10 years of age, and death occurs typically during the second or third decade of life.

Mucopolysaccharidosis 7

A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPS7 is an autosomal recessive form with a highly variable phenotype, ranging from severe lethal hydrops fetalis to mild forms with survival into adulthood. Most patients with the intermediate phenotype show hepatomegaly, skeletal anomalies, coarse facies, and variable degrees of mental impairment.

Mitochondrial complex IV deficiency, nuclear type 7

An autosomal recessive mitochondrial disorder characterized by encephalomyopathy resulting in variable clinical manifestations. Features include muscle weakness, gait disturbances, neurodegeneration, cognitive decline, metabolic acidosis, feeding difficulties, poor overall growth, cortical visual impairment, and hypertrophic cardiomyopathy. Serum lactate levels are increased. Patient tissues show decreased levels and activity of mitochondrial respiratory complex IV.

Mitochondrial complex IV deficiency, nuclear type 3

An autosomal recessive mitochondrial disorder characterized by cytochrome c oxidase deficiency. Clinical features include muscle weakness, hypotonia, ataxia, ptosis, metabolic acidosis, poor feeding, delayed motor development, anemia, sensorineural hearing loss, and cardiomyopathy.

Mitochondrial complex IV deficiency, nuclear type 1

An autosomal recessive disorder of the mitochondrial respiratory chain characterized by early-onset, rapidly progressive encephalopathy, neurodegeneration, and loss of motor and cognitive skills. Affected individuals show hypotonia, failure to thrive, loss of the ability to sit or walk, poor communication, poor eye contact, oculomotor abnormalities, as well as deafness, ataxia, tremor, and brisk tendon reflexes. Brain imaging shows bilateral symmetric lesions in the basal ganglia. Lactate levels in serum and cerebrospinal fluid are increased. Patient tissues show decreased levels and activity of mitochondrial respiratory complex IV. Death in childhood may occur, often due to central respiratory failure.

Mitochondrial complex II deficiency, nuclear type 1

A disorder of the mitochondrial respiratory chain with heterogeneous clinical manifestations. Clinical features include psychomotor regression in infants, poor growth with lack of speech development, severe spastic quadriplegia, dystonia, progressive leukoencephalopathy, muscle weakness, exercise intolerance, cardiomyopathy. Some patients manifest Leigh syndrome or Kearns-Sayre syndrome. MC2DN1 inheritance is autosomal recessive.

Mitochondrial complex I deficiency, nuclear type 6

A form of mitochondrial complex I deficiency, the most common biochemical signature of mitochondrial disorders, a group of highly heterogeneous conditions characterized by defective oxidative phosphorylation, which collectively affects 1 in 5-10000 live births. Clinical disorders have variable severity, ranging from lethal neonatal disease to adult-onset neurodegenerative disorders. Phenotypes include macrocephaly with progressive leukodystrophy, non-specific encephalopathy, cardiomyopathy, myopathy, liver disease, Leigh syndrome, Leber hereditary optic neuropathy, and some forms of Parkinson disease. MC1DN6 transmission pattern is consistent with autosomal recessive inheritance.

Mitochondrial complex I deficiency, nuclear type 37

A form of mitochondrial complex I deficiency, the most common biochemical signature of mitochondrial disorders, a group of highly heterogeneous conditions characterized by defective oxidative phosphorylation, which collectively affects 1 in 5-10000 live births. Clinical disorders have variable severity, ranging from lethal neonatal disease to adult-onset neurodegenerative disorders. Phenotypes include macrocephaly with progressive leukodystrophy, non-specific encephalopathy, cardiomyopathy, myopathy, liver disease, Leigh syndrome, Leber hereditary optic neuropathy, and some forms of Parkinson disease. MC1DN37 features include developmental delay, cerebral atrophy, epilepsy, growth retardation, congenital myopathy with disproportion of fibers, and severely decreased activity of complex I. MC1DN37 transmission pattern is consistent with autosomal recessive inheritance.

Mitochondrial complex I deficiency, nuclear type 17

A form of mitochondrial complex I deficiency, the most common biochemical signature of mitochondrial disorders, a group of highly heterogeneous conditions characterized by defective oxidative phosphorylation, which collectively affects 1 in 5-10000 live births. Clinical disorders have variable severity, ranging from lethal neonatal disease to adult-onset neurodegenerative disorders. Phenotypes include macrocephaly with progressive leukodystrophy, non-specific encephalopathy, cardiomyopathy, myopathy, liver disease, Leigh syndrome, Leber hereditary optic neuropathy, and some forms of Parkinson disease. MC1DN17 transmission pattern is consistent with autosomal recessive inheritance.

Mitochondrial DNA depletion syndrome 17

An autosomal recessive mitochondrial disorder characterized by childhood onset of rapidly progressive encephalopathy, stroke-like episodes, lactic acidosis, hypocitrullinemia, multiple defects of oxidative phosphorylation, mitochondrial complex I and IV deficiency, and reduced mtDNA copy number.

Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant, 2

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.

Lynch syndrome 4

A form of Lynch syndrome, an autosomal dominant disease associated with marked increase in cancer susceptibility. It is characterized by a familial predisposition to early-onset colorectal carcinoma (CRC) and extra-colonic tumors of the gastrointestinal, urological and female reproductive tracts. Lynch syndrome is reported to be the most common form of inherited colorectal cancer in the Western world. Clinically, it is often divided into two subgroups. Type I is characterized by hereditary predisposition to colorectal cancer, a young age of onset, and carcinoma observed in the proximal colon. Type II is characterized by increased risk for cancers in certain tissues such as the uterus, ovary, breast, stomach, small intestine, skin, and larynx in addition to the colon. Diagnosis of classical Lynch syndrome is based on the Amsterdam criteria: 3 or more relatives affected by colorectal cancer, one a first degree relative of the other two; 2 or more generation affected; 1 or more colorectal cancers presenting before 50 years of age; exclusion of hereditary polyposis syndromes. The term 'suspected Lynch syndrome' or 'incomplete Lynch syndrome' can be used to describe families who do not or only partially fulfill the Amsterdam criteria, but in whom a genetic basis for colon cancer is strongly suspected.

Lynch syndrome 5

A form of Lynch syndrome, an autosomal dominant disease associated with marked increase in cancer susceptibility. It is characterized by a familial predisposition to early-onset colorectal carcinoma (CRC) and extra-colonic tumors of the gastrointestinal, urological and female reproductive tracts. Lynch syndrome is reported to be the most common form of inherited colorectal cancer in the Western world. Clinically, it is often divided into two subgroups. Type I is characterized by hereditary predisposition to colorectal cancer, a young age of onset, and carcinoma observed in the proximal colon. Type II is characterized by increased risk for cancers in certain tissues such as the uterus, ovary, breast, stomach, small intestine, skin, and larynx in addition to the colon. Diagnosis of classical Lynch syndrome is based on the Amsterdam criteria: 3 or more relatives affected by colorectal cancer, one a first degree relative of the other two; 2 or more generation affected; 1 or more colorectal cancers presenting before 50 years of age; exclusion of hereditary polyposis syndromes. The term 'suspected Lynch syndrome' or 'incomplete Lynch syndrome' can be used to describe families who do not or only partially fulfill the Amsterdam criteria, but in whom a genetic basis for colon cancer is strongly suspected.

Mevalonic aciduria

Accumulation of mevalonic acid which causes a variety of symptoms such as psychomotor retardation, dysmorphic features, cataracts, hepatosplenomegaly, lymphadenopathy, anemia, hypotonia, myopathy, and ataxia.

Hyperinsulinemic hypoglycemia, familial, 2

A form of hyperinsulinemic hypoglycemia, a clinically and genetically heterogeneous disorder characterized by inappropriate insulin secretion from the pancreatic beta-cells in the presence of low blood glucose levels. HHF2 is a common cause of persistent hypoglycemia in infancy. Unless early and aggressive intervention is undertaken, brain damage from recurrent episodes of hypoglycemia may occur. HHF2 inheritance can be autosomal dominant or autosomal recessive.

Malonyl-CoA decarboxylase deficiency

Autosomal recessive disease characterized by abdominal pain, chronic constipation, episodic vomiting, metabolic acidosis and malonic aciduria.

Pancreatic agenesis 1

A disease characterized by isolated hypoplasia or agenesis of the pancreas, pancreatic beta-cell failure resulting in neonatal insulin-dependent diabetes mellitus, and exocrine pancreatic insufficiency.

Lipodystrophy, familial partial, 4

An autosomal dominant form of lipodystrophy characterized by loss of subcutaneous adipose tissue primarily affecting the lower limbs, insulin-resistant diabetes mellitus, hypertriglyceridemia, and hypertension.

Retinitis pigmentosa 7

A retinal dystrophy belonging to the group of pigmentary retinopathies. Retinitis pigmentosa is characterized by retinal pigment deposits visible on fundus examination and primary loss of rod photoreceptor cells followed by secondary loss of cone photoreceptors. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well.

Intellectual developmental disorder, autosomal recessive 81

An autosomal recessive disorder characterized by variable features including mild to severe developmental delay, hypotonia, feeding difficulties, extreme fatigue, and neurobehavioral abnormalities.

Intellectual developmental disorder, autosomal recessive 61

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRT61 patients manifest delayed psychomotor development, moderate to severe intellectual disability, and variable dysmorphic facial features. Refractory seizures and brain abnormalities are present in severely affected patients.

Intellectual developmental disorder, autosomal recessive 6

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRT6 patients display mild to severe intellectual disability and psychomotor development delay in early childhood. Patients do not have neurologic problems, congenital malformations, or facial dysmorphism. Body height, weight, and head circumference are normal.

Intellectual developmental disorder, autosomal recessive 59

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period.

Hypomagnesemia 1

A disorder due to a primary defect in intestinal magnesium absorption. It is characterized by low levels of serum magnesium alongside with a normal renal magnesium secretion, secondary hypocalcemia and calcinocis. Affected individuals show neurologic symptoms of hypomagnesemic hypocalcemia, including seizures and muscle spasms, during infancy. Hypocalcemia is secondary to parathyroid failure resulting from magnesium deficiency. Untreated, the disorder may be fatal or may result in neurological damage.

Hyperphenylalaninemia, mild, non-BH4-deficient

An autosomal recessive disorder characterized by increased serum phenylalanine, normal BH4 metabolism, and highly variable neurologic defects, including movement abnormalities and intellectual disability.

Methionine adenosyltransferase deficiency

An inborn error of metabolism resulting in isolated hypermethioninemia. Most patients have no clinical abnormalities, although some neurologic symptoms may be present in rare cases with severe loss of methionine adenosyltransferase activity.

Hypermethioninemia due to adenosine kinase deficiency

A metabolic disorder characterized by global developmental delay, early-onset seizures, mild dysmorphic features, and characteristic biochemical anomalies, including persistent hypermethioninemia with increased levels of S-adenosylmethionine and S-adenosylhomocysteine. Homocysteine levels are typically normal.

Hypobetalipoproteinemia, familial, 1

A disorder of lipid metabolism characterized by less than 5th percentile age- and sex-specific levels of low density lipoproteins, and dietary fat malabsorption. Clinical presentation may vary from no symptoms to severe gastrointestinal and neurological dysfunction similar to abetalipoproteinemia.