CONGENITAL MYOPATHY WITH MOSAIC FIBERS AND INTERLACING SARCOMERES - ANEW STRUCTURAL MYOPATHY

A 44-year-old man presenting with dyspnoic attacks was found to be aff ected with congenital myopathy, rigid spine, restrictive respiratory i nsufficiency and cardiomyopathy. Muscle biopsy showed type 1 fiber pre dominance (65.7%) and hypotrophy, and characteristic changes in 43.9% of the type 1 fibers, consisting in alternating pale and dark staining on alkaline ATPase reacted sections in a mosaic pattern. Ultrastructu ral examination demonstrated bands of myofibrils at right angles or sk ew to the remaining myofibrils transversing the fibers. Myofibrillar d isarray was always associated with loss of the Z-discs and actin filam ents, and often with aggregation of mitochondria. The muscle biopsy fi ndings in this patient suggest a new entity of congenital myopathy wit h clinical features of rigid spine, cardiomyopathy and restrictive res piratory insufficiency, characterized by peculiar abnormalities of ATP ase staining in a mosaic pattern and, ultrastructurally, by zones of d isorientation of the sarcomeres.