MedGen

Any retinitis pigmentosa in which the cause of the disease is a mutation in the CNGB1 gene. [from MONDO]

Waardenburg syndrome type I (WS1) is an auditory-pigmentary disorder comprising congenital sensorineural hearing loss and pigmentary disturbances of the iris, hair, and skin along with dystopia canthorum (lateral displacement of the inner canthi). The hearing loss in WS1, observed in approximately 60% of affected individuals, is congenital, typically non-progressive, either unilateral or bilateral, and sensorineural. Most commonly, hearing loss in WS1 is bilateral and profound (>100 dB). The majority of individuals with WS1 have either a white forelock or early graying of the scalp hair before age 30 years. The classic white forelock observed in approximately 45% of individuals is the most common hair pigmentation anomaly seen in WS1. Affected individuals may have complete heterochromia iridium, partial/segmental heterochromia, or hypoplastic or brilliant blue irides. Congenital leukoderma is frequently seen on the face, trunk, or limbs. [from GeneReviews]

Hyperkalemic periodic paralysis (hyperPP) is characterized by attacks of flaccid limb weakness (which may also include weakness of the muscles of the eyes, throat, breathing muscles, and trunk), hyperkalemia (serum potassium concentration >5 mmol/L) or an increase of serum potassium concentration of at least 1.5 mmol/L during an attack of weakness and/or provoking/worsening of an attack by oral potassium intake, normal serum potassium between attacks, and onset before age 20 years. In approximately half of affected individuals, attacks of flaccid muscle weakness begin in the first decade of life, with 25% reporting their first attack at age ten years or older. Initially infrequent, the attacks then increase in frequency and severity over time until approximately age 50 years, after which the frequency of attacks declines considerably. The major attack trigger is eating potassium-rich foods; other triggers include: cold environment; rest after exercise, stress, or fatigue; alcohol; hunger; and changes in activity level. A spontaneous attack commonly starts in the morning before breakfast, lasts for 15 minutes to one hour, and then passes. Individuals with hyperPP frequently have myotonia (muscle stiffness), especially around the time of an episode of weakness. Paramyotonia (muscle stiffness aggravated by cold and exercise) is present in about 45% of affected individuals. More than 80% of individuals with hyperPP older than age 40 years report permanent muscle weakness and about one third develop a chronic progressive myopathy. [from GeneReviews]

Charcot-Marie-Tooth disease is a clinically and genetically heterogeneous 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. Classification CMT neuropathy is subdivided into CMT1 (see 118200) and CMT2 (see 118210) types on the basis of electrophysiologic and neuropathologic criteria. CMT1, or hereditary motor and sensory neuropathy type I (HMSN I), is a demyelinating neuropathy, whereas CMT2, or HMSN II, is an axonal neuropathy. Most patients with CMT are classified as having CMT1 or CMT2 by use of a cut-off value of 38 m/s for the motor median nerve conduction velocity (NCV). However, in some families with CMT, patients have motor median NCVs ranging from 25 to 45 m/s. Families of this type were reported by Salisachs (1974) and Davis et al. (1978). Davis et al. (1978) proposed that this form be designated 'intermediate' CMT. Claeys et al. (2009) stated that some CMT families may have an even broader range of NCV than 25 to 45 m/s, with the lowest levels around 25 and the highest levels within the normal range (50+ m/s). They also suggested that the term 'intermediate' should not be used to describe a single NCV value, but rather the CMT subtype at the level of the family (e.g., in families with a range or combinations of NCV values). Berciano et al. (2017) provided a detailed review of the different forms of intermediate CMT, noting that diagnoses may be controversial because of variable classification issues. The authors presented an algorithm for the interpretation of electrophysiologic studies in CMT, and suggested that nerve conduction studies should be conducted on the upper arm (axilla to elbow). They noted that distal axonal degeneration can result in secondary myelination defects, which may cause significantly decreased motor NCV and CMAP values that may be misinterpreted. Genetic Heterogeneity of Autosomal Dominant Intermediate CMT In addition to CMTDIB, which is caused by mutation in the DNM2 gene, other forms of dominant intermediate CMT include CMTDIA (620378), mapped to chromosome 10q24-q25; CMTDIC (608323), caused by mutation in the YARS gene (603623) on chromosome 1p35; CMTDID (607791), caused by mutation in the MPZ gene (159440) on chromosome 1q22; CMTDIE with focal segmental glomerulosclerosis (CMTDIE; 614455), caused by mutation in the INF2 gene (610982) on chromosome 14q32; CMTDIF (615185), caused by mutation in the GNB4 gene (610863) on chromosome 3q26; and CMTDIG (617882), caused by mutation in the NEFL gene (162280) on chromosome 8p21. [from OMIM]

Developmental and epileptic encephalopathy-45 (DEE45) is a neurologic disorder characterized by global developmental delay apparent in infancy or early childhood and onset of seizures within the first 12 months of life. Affected individuals have severely impaired intellectual development, hypotonia, and other persistent neurologic deficits (summary by Burgess et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350. [from OMIM]

A rare hereditary motor and sensory neuropathy with characteristics of intermediate motor median nerve conduction velocities (usually between 25 and 45 m/s) and signs of both axonal degeneration and demyelination without onion bulbs in nerve biopsies. It presents with usual Charcot-Marie-Tooth disease clinical features of variable severity (progressive muscle weakness and atrophy of the distal extremities, distal sensory loss, reduced or absent deep tendon reflexes, and feet deformities). Other findings in some of the families include debilitating neuropathic pain and mild postural/kinetic upper limb tremor. [from SNOMEDCT_US]

A rare pure or complex form of hereditary spastic paraplegia with characteristics of onset in infancy of progressive lower limb spasticity, abnormal gait, increased deep tendon reflexes and extensor plantar responses that may be associated with intellectual disability. Additional signs such as contractures in the lower limbs, amyotrophy, clubfoot and optic atrophy, have also been reported. Caused by homozygous mutation in the NT5C2 gene on chromosome 10q24. [from SNOMEDCT_US]

Oculopharyngeal muscular dystrophy (OPMD) is characterized by ptosis and dysphagia due to selective involvement of the muscles of the eyelids and pharynx, respectively. For the vast majority of individuals with typical OPMD, the mean age of onset of ptosis is usually 48 years and of dysphagia 50 years; in 5%-10% of individuals with severe OPMD, onset of ptosis and dysphagia occur before age 45 years and is associated with lower limb girdle weakness starting around age 60 years. Swallowing difficulties, which determine prognosis, increase the risk for potentially life-threatening aspiration pneumonia and poor nutrition. Other manifestations as the disease progresses can include limitation of upward gaze, tongue atrophy and weakness, chewing difficulties, wet voice, facial muscle weakness, axial muscle weakness, and proximal limb girdle weakness predominantly in lower limbs. Some individuals with severe involvement will eventually need a wheelchair. Neuropsychological tests have shown altered scores in executive functions in some. [from GeneReviews]

Intrahepatic cholestasis of pregnancy is a reversible form of cholestasis that occurs most often in the third trimester of pregnancy and recurs in 45 to 70% of subsequent pregnancies. Symptoms include pruritus, jaundice, increased serum bile salts, and abnormal liver enzymes, all of which resolve rapidly after delivery. However, the condition is associated with fetal complications, including placental insufficiency, premature labor, fetal distress, and intrauterine death. Women with ICP are also susceptible to oral contraceptive-induced cholestasis (OCIC). Ursodeoxycholic acid (UDCA) is an effective treatment for conditions caused by ABCB4 mutations (summary by Pasmant et al., 2012). Mutation in the ABCB4 gene accounts for about 15% of ICP cases (summary by Ziol et al., 2008). For a discussion of genetic heterogeneity of ICP, see ICP1 (147480). [from OMIM]

Intrahepatic cholestasis of pregnancy is a reversible form of cholestasis that occurs most often in the third trimester of pregnancy and recurs in 45 to 70% of subsequent pregnancies. Symptoms include pruritus, jaundice, increased serum bile salts, and abnormal liver enzymes, all of which resolve rapidly after delivery. However, the condition is associated with fetal complications, including placental insufficiency, premature labor, fetal distress, and intrauterine death. Some women with ICP may also be susceptible to oral contraceptive-induced cholestasis (OCIC) (summary by Pasmant et al., 2012). Genetic Heterogeneity of Intrahepatic Cholestasis of Pregnancy See also ICP3 (614972), caused by mutation in the ABCB4 gene (171060). [from OMIM]

Immunodeficiency-45 (IMD45) is an autosomal recessive immunologic disorder with specific clinical features. Patients may present with life-threatening respiratory infections with COVID-19 or influenza and with severe adverse reactions (e.g., meningoencephalitis and hemophagocytic lymphohistiocytosis) to live attenuated viral vaccination. Laboratory studies show impaired response to alpha-interferon (see 147660), impaired type I interferon signature after stimulation, and heightened vulnerability to multiple viruses in vitro (summary by Duncan et al., 2015; Passarelli et al., 2020; Duncan et al., 2022). [from OMIM]

An autosomal recessive nonsyndromic deafness that has material basis in variation in the chromosome region 1q43-q44. [from MONDO]

Any early-onset non-syndromic cataract in which the cause of the disease is a mutation in the SIPA1L3 gene. [from MONDO]

Primary ciliary dyskinesia-45 (CILD45) is an autosomal recessive disorder characterized by recurrent sinopulmonary infections resulting from defective mucociliary clearance. Affected individuals have onset of symptoms in infancy or early childhood, and the repetitive nature of the disorder may result in bronchiectasis. Nasal nitric oxide may be decreased, but patients do not have situs abnormalities. Male patients have infertility due to immotile sperm (summary by Thomas et al., 2020). For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400). [from OMIM]

A rare autosomal dominant cerebellar ataxia with characteristics of slowly progressive late-onset gait and limb ataxia, dysarthria and variable nystagmus. Brain imaging reveals cerebellar atrophy. [from SNOMEDCT_US]

Any non-syndromic X-linked intellectual disability in which the cause of the disease is a mutation in the ZNF81 gene. [from MONDO]

Rheumatic fever (RF) is a delayed sequel to throat infection by Streptococcus pyogenes and affects susceptible untreated children. The disease manifests as polyarthritis, carditis, chorea, erythema marginatum, and/or subcutaneous nodules. Nearly 75% of affected children display arthritis and 30 to 45% develop carditis, which causes heart damage with pericardial, myocardial, and endocardial involvement followed by progressive and permanent valvular lesions leading to rheumatic heart disease (RHD) (summary by Guilherme et al., 2007). [from OMIM]

Combined oxidative phosphorylation deficiency-45 (COXPD45) is an autosomal recessive multisystem disorder characterized by poor overall growth apparent from infancy, global developmental delay, seizures, and acute progressive neurologic deterioration with loss of skills. Other features may include dysmorphic facies and lesions on brain imaging. Laboratory studies show increased serum lactate and COXPD in patient tissues, consistent with a mitochondrial defect (summary by Serre et al., 2013). For discussion of genetic heterogeneity of combined oxidative phosphorylation deficiency, see COXPD1 (609060). [from OMIM]