Congenital myopathies are reviewed by neuropathology researchers in New Delhi, India, and Mainz, Germany. The term ‘congenital myopathy’ (CM) was introduced with the discovery of ‘central core disease,’ a non-progressive myopathy described by Shy and Magee (1956). Molecular genetics, enzyme and immunohistochemical tests and electron microscopy have led to a better understanding of CM and their classification. CM is either structured or unstructured, with or without structural changes. Structured CM include, central core disease (autosomal dominant, mildly progressive or static; or autosomal recessive, more severe with onset in the first decade); multi-minicore disease (proximal muscle weakness, spinal rigidity, scoliosis, respiratory impairment, and external ophthalmoplegia); myotubular myopathies (type 1 fiber atrophy and central nuclei); X-linked myotubular myopathy (rapidly fatal in newborn boys, presenting with hypotonia and respiratory insufficiency, and arthrogryposis multiplex); centronuclear myopathy (autosomal dominant or recessive, or sporadic, neonatal and childhood forms, mildly progressive, central nuclei, type 1 predominance); nemaline myopathy (thread like rod inclusions on Gomori trichrome stains, 6 different forms, congenital to adult); actin aggregate myopathy (similar to nemaline myopathy, early onset, rapid course, rarely benign); desminopathy (slowly progressive, second to fourth decade distal weakness onset, cardiomyopathy, autosomal dominant or recessive); a-B-crystallinopathy (similar to desminopathies, a myofibrillary myopathy); hyaline body myopathy (subsarcolemmal hyalinized bodies, rich in myofibrillary ATPase and myosin). Unstructured CM: congenital fiber type disproportion (non-progressive childhood CM with relatively good prognosis, type 1 fiber predominance).
No clinical symptomatology is specific for an individual CM, but some clinical findings are more frequent in certain CMs; eg. ptosis or extraocular muscle weakness in multicore disease, nemaline myopathy, centronuclear myopathy, and congenital fiber type disproportion; scoliosis in desminopathies, and central core disease. [1]
COMMENT. An expertise in enzyme and immunohistochemical methods, electron microscopy, and molecular genetics is required to distinguish the rapidly expanding differential diagnosis of congenital myopathies. Clinical symptomatology is largely nonspecific.