Structural changes in the early stages of Duchenne muscular dystrophy.

The finding of a relative absence of degeneration and regeneration in a muscle biopsy taken at 2½ weeks of age from a boy who later showed the florid pathological changes of preclinical Duchenne muscular dystrophy prompted a review of muscle biopsies taken from boys in the preclinical and early clinical stages of this disease. Only one other biopsy obtained in the first year of life was available. In this, taken at 2 months, there were active changes present. These findings suggest that biopsies taken to detect preclinical cases should not be performed at less than 2 months of age, and raise the possibility of the existence of a stage in Duchenne muscular dystrophy before active degeneration when the muscle shows little or no change on light microscopy.