MedGen

AMED syndrome (AMEDS) is an autosomal recessive digenic multisystem disorder characterized by global developmental delay with impaired intellectual development, onset of bone marrow failure and myelodysplastic syndrome (MDS) in childhood, and poor overall growth with short stature (summary by Oka et al., 2020). For a discussion of genetic heterogeneity of bone marrow failure syndrome (BMFS), see BMFS1 (614675). [from OMIM]

Oculocutaneous albinism type VIII (OCA8) is characterized by mild hair and skin hypopigmentation, associated with ocular features including nystagmus, reduced visual acuity, iris transillumination, and hypopigmentation of the retina (Pennamen et al., 2021). [from OMIM]

Developmental and epileptic encephalopathy-82 (DEE82) is an autosomal recessive mitochondriopathy manifest as early-onset metabolic epileptic encephalopathy. Soon after birth, affected individuals exhibit hypotonia, feeding difficulties, and global developmental delay even before the onset of seizures in the first year of life. The severity is variable, but all patients have severely impaired intellectual development with absent speech and spastic tetraplegia. Other features include poor overall growth with microcephaly and recurrent infections. Brain imaging shows cerebral atrophy, thin corpus callosum, cerebellar hypoplasia, and white matter abnormalities. Laboratory studies show increased serum lactate and ammonia. Importantly, treatment with combined pyridoxine and serine can result in significant improvement in seizures as well as some mild developmental progress (summary by van Karnebeek et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350. [from OMIM]

Dopamine beta-hydroxylase (DBH) deficiency is characterized by lack of sympathetic noradrenergic function but normal parasympathetic and sympathetic cholinergic function. Affected individuals exhibit profound deficits in autonomic regulation of cardiovascular function that predispose to orthostatic hypotension. Although DBH deficiency appears to be present from birth, the diagnosis is not generally recognized until late childhood. The combination of ptosis of the eyelids in infants and children, together with hypotension, is suggestive of the disease. In the perinatal period, DBH deficiency has been complicated by vomiting, dehydration, hypotension, hypothermia, and hypoglycemia requiring repeated hospitalization; children have reduced exercise capacity. By early adulthood, individuals have profound orthostatic hypotension, greatly reduced exercise tolerance, ptosis of the eyelids, and nasal stuffiness. Presyncopal symptoms include dizziness, blurred vision, dyspnea, nuchal discomfort, and chest pain; symptoms may worsen in hot environments or after heavy meals or alcohol ingestion. Life expectancy is unknown, but some affected individuals have lived beyond age 60 years. [from GeneReviews]

Researchers have identified multiple types of oculocutaneous albinism, which are distinguished by their specific skin, hair, and eye color changes and by their genetic cause. Oculocutaneous albinism type 1 is characterized by white hair, very pale skin, and light-colored irises. Type 2 is typically less severe than type 1; the skin is usually a creamy white color and hair may be light yellow, blond, or light brown. Type 3 includes a form of albinism called rufous oculocutaneous albinism, which usually affects dark-skinned people. Affected individuals have reddish-brown skin, ginger or red hair, and hazel or brown irises. Type 3 is often associated with milder vision abnormalities than the other forms of oculocutaneous albinism. Type 4 has signs and symptoms similar to those seen with type 2.

Oculocutaneous albinism is a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes. Affected individuals typically have very fair skin and white or light-colored hair. Long-term sun exposure greatly increases the risk of skin damage and skin cancers, including an aggressive form of skin cancer called melanoma, in people with this condition. Oculocutaneous albinism also reduces pigmentation of the colored part of the eye (the iris) and the light-sensitive tissue at the back of the eye (the retina). People with this condition usually have vision problems such as reduced sharpness; rapid, involuntary eye movements (nystagmus); and increased sensitivity to light (photophobia).

Several additional types of this disorder have been proposed, each affecting one or a few families. [from MedlinePlus Genetics]

Any isolated microphthalmia in which the cause of the disease is a mutation in the ALDH1A3 gene. [from MONDO]

Deficiency of maleylacetoacetate isomerase (MAAID) is characterized by mild elevations in succinylacetone in blood and urine, usually identified by newborn screening. Liver function and coagulation are normal. MAAID is differentiated from hepatorenal tyrosinemia (TYRSN1; 276700), which is also identified by hypersuccinylacetonemia on newborn screening but is a severe disorder with hepatic failure, renal tubulopathy, rickets, and porphyria-like neurologic crises. MAAID and TYRSN1 are caused by mutations in genes encoding the penultimate and ultimate enzymes, respectively, in the phenylalanine and tyrosine degradation pathway (summary by Yang et al., 2017). [from OMIM]

Generally, Parkinson's disease that begins after age 50 is called late-onset disease. The condition is described as early-onset disease if signs and symptoms begin before age 50. Early-onset cases that begin before age 20 are sometimes referred to as juvenile-onset Parkinson's disease.

Parkinson's disease can also affect emotions and thinking ability (cognition). Some affected individuals develop psychiatric conditions such as depression and visual hallucinations. People with Parkinson's disease also have an increased risk of developing dementia, which is a decline in intellectual functions including judgment and memory.

Often the first symptom of Parkinson's disease is trembling or shaking (tremor) of a limb, especially when the body is at rest. Typically, the tremor begins on one side of the body, usually in one hand. Tremors can also affect the arms, legs, feet, and face. Other characteristic symptoms of Parkinson's disease include rigidity or stiffness of the limbs and torso, slow movement (bradykinesia) or an inability to move (akinesia), and impaired balance and coordination (postural instability). These symptoms worsen slowly over time.

Parkinson's disease is a progressive disorder of the nervous system. The disorder affects several regions of the brain, especially an area called the substantia nigra that controls balance and movement. [from MedlinePlus Genetics]

Hawkinsinuria (HWKS) is an autosomal dominant inborn error of metabolism. Metabolic acidosis and tyrosinemia are transient, and symptoms improve within the first year of life. Patients continue to excrete the hawkinsin metabolite in their urine throughout life (Danks et al., 1975; Tomoeda et al., 2000). [from OMIM]

The DSM-IV (American Psychiatric Association, 1994) defines panic disorder as the spontaneous, unexpected occurrence of panic attacks followed by persistent concern, worry, and anxiety about having additional panic attacks. Panic attacks are defined as a discrete period of intense fear or discomfort in which at least 4 of 13 symptom criteria are met that develop abruptly and reach a peak within 10 minutes. Some of these criteria include cardiac palpitations, sweating, feelings of choking, fear of losing control, and fear of dying. Panic disorder is divided into panic disorder with or without accompanying agoraphobia. However, agoraphobia can also occur without panic disorder, and panic attacks can occur in the absence of panic disorder. Comorbidity with depressive and addictive disorders is frequent. Barlow et al. (1994) and Smoller and Tsuang (1998) noted that because the diagnostic criteria remain purely clinical, the nosology of anxiety disorders, such as panic disorder, is controversial and evolving. Therefore, it is difficult to do genetic studies because of the difficulty in delineating overlapping phenotypes within the broader context of anxiety disorders. For example, there may be overlap of panic with specific phobias, variable expressivity of panic and anxiety or depression, or phenocopies within a family. The terms 'anxiety neurosis' and 'phobic neurosis' were used in the past (before the DSM-III in 1980) to encompass all of these disorders. Smoller and Tsuang (1998) suggested that dimensional personality traits, such as shyness, behavioral inhibition, and neuroticism (see 607834), could be used to define an anxiety phenotype. Schumacher et al. (2011) provided a review of the genetics of panic disorder. They noted that there is high (80%) comorbidity with other psychiatric disorders, including agoraphobia, mood disorders, substance abuse, and other anxiety disorders. Associated personality traits include anxiety sensitivity, behavioral inhibition, neuroticism, and harm avoidance. Women are more susceptible to development of the disorder, which has an average age of onset at 23.6 years. Genetic Heterogeneity of Susceptibility to Panic Disorder Susceptibility to panic disorder-1 (PAND1) has been mapped to chromosome 13q. See also PAND2 (607853), mapped to chromosome 9, and PAND3 (609985), mapped to chromosome 4. [from OMIM]

Tyrosine hydroxylase (TH) deficiency is associated with a broad phenotypic spectrum. Based on severity of symptoms/signs as well as responsiveness to levodopa therapy, clinical phenotypes caused by pathogenic variants in TH are divided into (1) TH-deficient dopa-responsive dystonia (the mild form of TH deficiency), (2) TH-deficient infantile parkinsonism with motor delay (the severe form), and (3) TH-deficient progressive infantile encephalopathy (the very severe form). In individuals with TH-deficient dopa-responsive dystonia (DYT5b, DYT-TH), onset is between age 12 months and 12 years; initial symptoms are typically lower-limb dystonia and/or difficulty in walking. Diurnal fluctuation of symptoms (worsening of the symptoms toward the evening and their alleviation in the morning after sleep) may be present. In most individuals with TH-deficient infantile parkinsonism with motor delay, onset is between age three and 12 months. In contrast to TH-deficient DRD, motor milestones are overtly delayed in this severe form. Affected infants demonstrate truncal hypotonia and parkinsonian symptoms and signs (hypokinesia, rigidity of extremities, and/or tremor). In individuals with TH-deficient progressive infantile encephalopathy, onset is before age three to six months. Fetal distress is reported in most. Affected individuals have marked delay in motor development, truncal hypotonia, severe hypokinesia, limb hypertonia (rigidity and/or spasticity), hyperreflexia, oculogyric crises, ptosis, intellectual disability, and paroxysmal periods of lethargy (with increased sweating and drooling) alternating with irritability. [from GeneReviews]

Juvenile idiopathic arthritis refers to a group of conditions involving joint inflammation (arthritis) that first appears before the age of 16. This condition is an autoimmune disorder, which means that the immune system malfunctions and attacks the body's organs and tissues, in this case the joints.

Researchers have described seven types of juvenile idiopathic arthritis. The types are distinguished by their signs and symptoms, the number of joints affected, the results of laboratory tests, and the family history.

Systemic juvenile idiopathic arthritis causes inflammation in one or more joints. A high daily fever that lasts at least 2 weeks either precedes or accompanies the arthritis. Individuals with systemic arthritis may also have a skin rash or enlargement of the lymph nodes (lymphadenopathy), liver (hepatomegaly), or spleen (splenomegaly).

Oligoarticular juvenile idiopathic arthritis (also known as oligoarthritis) is marked by the occurrence of arthritis in four or fewer joints in the first 6 months of the disease. It is divided into two subtypes depending on the course of disease. If the arthritis is confined to four or fewer joints after 6 months, then the condition is classified as persistent oligoarthritis. If more than four joints are affected after 6 months, this condition is classified as extended oligoarthritis. Individuals with oligoarthritis are at increased risk of developing inflammation of the eye (uveitis).

Rheumatoid factor positive polyarticular juvenile idiopathic arthritis (also known as polyarthritis, rheumatoid factor positive) causes inflammation in five or more joints within the first 6 months of the disease. Individuals with this condition also have a positive blood test for proteins called rheumatoid factors. This type of arthritis closely resembles rheumatoid arthritis as seen in adults.

Rheumatoid factor negative polyarticular juvenile idiopathic arthritis (also known as polyarthritis, rheumatoid factor negative) is also characterized by arthritis in five or more joints within the first 6 months of the disease. Individuals with this type, however, test negative for rheumatoid factor in the blood.

Psoriatic juvenile idiopathic arthritis involves arthritis that usually occurs in combination with a skin disorder called psoriasis. Psoriasis is a condition characterized by patches of red, irritated skin that are often covered by flaky white scales. Some affected individuals develop psoriasis before arthritis while others first develop arthritis. Other features of psoriatic arthritis include abnormalities of the fingers and nails or eye problems.

Enthesitis-related juvenile idiopathic arthritis is characterized by tenderness where the bone meets a tendon, ligament, or other connective tissue. The most commonly affected places are the hips, knees, and feet. This tenderness, known as enthesitis, accompanies the joint inflammation of arthritis. Enthesitis-related arthritis may also involve inflammation in parts of the body other than the joints.

The last type of juvenile idiopathic arthritis is called undifferentiated arthritis. This classification is given to affected individuals who do not fit into any of the above types or who fulfill the criteria for more than one type of juvenile idiopathic arthritis. [from MedlinePlus Genetics]

Oculocutaneous albinism type I is an autosomal recessive disorder characterized by absence of pigment in hair, skin, and eyes, and does not vary with race or age. Severe nystagmus, photophobia, and reduced visual acuity are common features. OCA type I is divided into 2 types: type IA, characterized by complete lack of tyrosinase activity due to production of an inactive enzyme, and type IB, characterized by reduced activity of tyrosinase. Although OCA caused by mutations in the TYR gene was classically known as 'tyrosinase-negative' OCA, Tripathi et al. (1992) noted that some patients with 'tyrosinase-positive' OCA may indeed have TYR mutations resulting in residual enzyme activity. These patients can be classified as having OCA1B. [from OMIM]

Approximately 10% of patients with congenital hypothyroidism harbor inborn errors of metabolism in one of the steps for thyroid hormone synthesis in thyrocytes (Vono-Toniolo et al., 2005). The most prevalent cause of thyroid dyshormonogenesis is TPO deficiency (Park and Chatterjee, 2005). Defects in TPO cause a severe form of congenital hypothyroidism characterized by a complete and immediate release of accumulated radioiodide from the thyroid after sodium perchlorate administration (Bakker et al., 2000). This release of radioiodide represents total iodine organification defect (TIOD), a disruption of the process by which iodide present in the thyroid is oxidized by hydrogen peroxide and bound to tyrosine residues in thyroglobulin (TG; 188450) to form iodotyrosine. [from OMIM]

Aromatic L-amino acid decarboxylase deficiency (AADCD) is an autosomal recessive inborn error in neurotransmitter metabolism that leads to combined serotonin and catecholamine deficiency (Abeling et al., 2000). The disorder is clinically characterized by vegetative symptoms, oculogyric crises, dystonia, and severe neurologic dysfunction, usually beginning in infancy or childhood (summary by Brun et al., 2010). [from OMIM]

Brunner syndrome is a recessive X-linked disorder characterized by impulsive aggressiveness and mild mental retardation associated with MAOA deficiency (Brunner et al., 1993). [from OMIM]

Several additional types of this disorder have been proposed, each affecting one or a few families.

Oculocutaneous albinism is a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes. Affected individuals typically have very fair skin and white or light-colored hair. Long-term sun exposure greatly increases the risk of skin damage and skin cancers, including an aggressive form of skin cancer called melanoma, in people with this condition. Oculocutaneous albinism also reduces pigmentation of the colored part of the eye (the iris) and the light-sensitive tissue at the back of the eye (the retina). People with this condition usually have vision problems such as reduced sharpness; rapid, involuntary eye movements (nystagmus); and increased sensitivity to light (photophobia).

Researchers have identified multiple types of oculocutaneous albinism, which are distinguished by their specific skin, hair, and eye color changes and by their genetic cause. Oculocutaneous albinism type 1 is characterized by white hair, very pale skin, and light-colored irises. Type 2 is typically less severe than type 1; the skin is usually a creamy white color and hair may be light yellow, blond, or light brown. Type 3 includes a form of albinism called rufous oculocutaneous albinism, which usually affects dark-skinned people. Affected individuals have reddish-brown skin, ginger or red hair, and hazel or brown irises. Type 3 is often associated with milder vision abnormalities than the other forms of oculocutaneous albinism. Type 4 has signs and symptoms similar to those seen with type 2. [from MedlinePlus Genetics]