A NEW CONGENITAL MUSCULAR-DYSTROPHY WITH MITOCHONDRIAL STRUCTURAL ABNORMALITIES

We report a new form of congenital muscular dystrophy (CMD) in 4 patie nts from three unrelated families with probable autosomal-recessive in heritance. All patients had the clinical characteristics of merosin-po sitive congenital muscular dystrophy, but had marked mental retardatio n. The disease was slowly progressive and 1 patient died from dilated cardiomyopathy at the age of 13 years. In addition to dystrophic chang es with necrosis and regeneration in muscle, the most striking finding was mitochondrial depletion in the center of the sarcoplasm. Mitochon dria at the periphery of fibers were markedly enlarged (''megaconial'' appearance) with complicated cristae, and contained a normal amount o f mitochondrial DNA by in situ hybridization. Mitochondrial enlargemen t may represent functional compensation for mitochondrial depletion in the central sarcoplasm, where myofibrillar degeneration occurred. (C) 1998 John Wiley & Sons, Inc.