MedGen

Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adulthood. The weakness is symmetric, proximal > distal, and progressive. Before the genetic basis of SMA was understood, it was classified into clinical subtypes based on maximum motor function achieved; however, it is now apparent that the phenotype of SMN1-associated SMA spans a continuum without clear delineation of subtypes. With supportive care only, poor weight gain with growth failure, restrictive lung disease, scoliosis, and joint contractures are common complications; however, newly available targeted treatment options are changing the natural history of this disease. [from GeneReviews]

Gyrate atrophy of the choroid and retina (GACR) due to deficiency of ornithine aminotransferase is 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 (summary by Peltola et al., 2002). See 238970 for another hyperornithinemia syndrome. [from OMIM]

Hereditary rippling muscle disease is an autosomal dominant disorder characterized by mechanically triggered contractions of skeletal muscle. In rippling muscle disease, mechanical stimulation leads to electrically silent muscle contractions that spread to neighboring fibers that cause visible ripples to move over the muscle. RMD is usually inherited as an autosomal dominant trait, but autosomal recessive inheritance has also been reported (Kubisch et al., 2005). Genetic Heterogeneity of Rippling Muscle Disease Another locus for RMD, designated RMD1 (600332), maps to chromosome 1q41. [from OMIM]

A rare metabolic myopathy with characteristics of muscle cramping and/or stiffness after exercise (especially during heat exposure), post-exertional rhabdomyolysis and myoglobinuria and elevation of serum creatine kinase. Caused by mutation in the SLC16A1 gene. [from SNOMEDCT_US]

A rare syndrome with characteristics of camptodactyly, muscle hypoplasia and weakness, skeletal anomalies, facial dysmorphism and abnormal dermatoglyphics. Dysmorphic features include facial asymmetry, hypertelorism, broad nasal bridge, long philtrum and a small mouth. Winging scapulae, scoliosis, syndactyly and clinodactyly are commonly observed. The affected patients usually have normal mental development. The molecular basis of the syndrome has not yet been elucidated. [from SNOMEDCT_US]

Abnormal results of investigations using electromyography (EMG). [from HPO]