Congenital myopathies and congenital muscular dystrophies

Congenital myopathies and congenital myopathic dystrophies are distinct gro ups of inherited diseases of muscle, genetically heterogeneous, that manife st in early life or infancy. Congenital myopathic dystrophy is characterize d by a dystrophic pattern, whereas no necrotic or degenerative changes are present in congenital myopathies. Much progress has been made in recent yea rs in clarifying the classification of the congenital myopathies. This is a clinically and genetically heterogeneous group of conditions originally cl assified according to unique morphological changes seen in muscle. Not unli ke the later-onset muscular dystrophies, the discovery of the genetic aetio logy of many of the congenital myopathies has led to a revamping of how the se conditions can now be diagnosed and this should enable physicians to giv e a more accurate prognosis to patients and their families. New mutations i n the ryanodine receptor, slow tropomyosin, troponin T1, actin, and nebulin genes have been described in the last 2 years. Clinical and genetic guidel ines for conditions like nemaline rod myopathy and central core disease hav e been suggested. The notion of minus and surplus protein myopathies has be en developed. Several groups of congenital myopathic. dystrophy have been i dentified. In the first category, without intellectual impairment or major structural brain abnormalities, half of the cases are merosin deficient due to mutations of the laminin alpha2 chain gene, If generally the muscular p henotype is severe, mild allelic variants have been reported with early ons et dystrophies and partial merosin deficiency. Among other pure congenital myopathic dystrophies unlinked to the laminin alpha2 gene, one form has bee n assigned to chromosome 1q42. In the group of congenital myopathic dystrop hies associated with mental retardation and structural brain abnormalities, two main entities are genetically characterized: (1) Fukuyama congenital m yopathic dystrophy, affecting the Japanese population, is due to fukutin ge ne mutations, and (2) the muscle eye brain syndrome assigned to chromosome 1p32-34. In several cases, the gene localization remains unknown. Curr Opin Neurol 14:575-562, (C) 2001 Lippincott Williams & Wilkins.