Histopathological changes in Duchenne muscular dystrophy

Quantitative estimations of the incidence of various abnormal histological features in Duchenne dystrophy were made on most of the muscle biopsies used for fibre size studies. The proportion of endomysial stroma was abnormally great in young patients and increased with the progression of the disease. The obliteration of myofascicular margins by proliferating endomysial stroma contributed to the increased proportion of perimysial stroma noted late in the disease. Morphological disorganization of myotendinous insertions was associated with fat accumulations at these locations. The presence, in control specimens, of central nuclei in fibres near their tendinous insertions was confirmed. Palisading mesenchymal cells were found at areas of myotendinous insertions in some infants. The presence of these features in normal muscles should be considered in the diagnostic appraisal of biopsy specimens. The occurrence of central nuclei in dystrophic muscle could not be correlated with any other histological feature. “Splitting” fibres and “nesting” fibres appeared to be merely histological variants of the same phenomenon. This process has been related to the variation in fibre size by statistical methods and appears to be the mechanism by which most small fibres replaced large and medium-sized fibres. These studies suggest that the presence of several distinct pathological features in muscle specimens from children with Duchenne muscular dystrophy may be caused by different reactive pathological processes which may obscure the specific inherited defect of this disease and aggravate muscle fibre destruction.