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The estimated prevalence of distal myopathy in the northern region of England is 1/300,000. Some forms have been identified with greater frequency in certain populations. For example, tibial muscular dystrophy is frequent in Finland with a prevalence of 1/5,000 and Welander distal myopathy occurs with greater frequency in Sweden.

Distal myopathy is characterized by progressive muscular weakness and atrophy beginning in the distal parts of upper and lower limbs with an extremely variable age of onset. Distal myopathy is a genetically heterogeneous group (currently comprising more than 20 genetic types) which affects different regions of the distal extremities and is classified according to clinical features, inheritance pattern, histopathological criteria, and molecular genetics. The main autosomal dominant forms of distal myopathy are Welander distal myopathy (weakness in the distal upper extremities which later progresses to distal lower extremity), tibial muscular dystrophy (mainly affects the front of the lower leg), distal myotilinopathy (progressive distal muscle weakness and peripheral neuropathy with hyporeflexia), late-onset distal myopathy, Markesbery-Griggs type (ZASP-related myofibrillar myopathy), Laing early-onset distal myopathy, distal myopathy with posterior leg and anterior hand involvement (distal ABD-filaminopathy), and adult-onset distal myopathy due to VCP mutation. The genetically confirmed autosomal recessive forms are distal myopathy, Nonaka type (GNE-myopathy, weakness in the anterior distal legs), Miyoshi myopathy (weakness in the distal lower extremity posterior compartment), nebulin-related early-onset distal myopathy and distal anoctaminopathy. The age at onset is extremely variable and for recessive varieties of distal myopathy, symptoms usually develop in early adult life whereas in the dominant Welander and tibial muscular dystrophy, the onset is usually later. However, in some disorders (i.e. Laing early-onset distal myopathy and nebulin-related early-onset distal myopathy) the onset may be during childhood, and even in infancy.

Distal myopathy is caused by defect or lack of specific proteins that play an essential role in the proper function and health of muscle cells. 15 causative genes have to date been associated with distal myopathy: ANO5 (11p15.1), CRYAB (11q22.3-q23.1), DES (2q35), DYSF (2p13.3), FLNC (7q32-q35), GNE (9p13.1), KLHL9 (9p22), LDB3 (10q22.3-q23.2), MATR3 (5q31.3), MYH7 (14q11.2-q13), MYOT (5q31.2), NEB (2q22), TIA1 (2p13), TTN (2q31) and VCP (9p13.3).

Distal myopathy can be inherited as an autosomal dominant or as an autosomal recessive trait.