Nemaline Myopathy: A Histopathologic and Histoohemical Study

Abstract

Detailed histopathological and histochemical studies performed on muscle biopsies from 5 patients with nemaline myopathyare described. Muscle biopsies were also studied from the clinically normal parents of 1 affected sibship. Protein histochemical studies demonstrated chemical similarity between the nemaline rods and the Z-bands. It was found that Nemaline myopathy could be successfully diagnosed by applying the methyl-green pyronin stain to fixed paraffin-embedded material. The absence of nemaline rods in 1 of 2 biopsies from each of 2 rather severely affected patients illustrated that a "negative" biopsy could be obtained from an abnormally weak muscle of a patient with the disease. A correlation between the severity of individual muscle weakness and the degree of nemaline rod accumulation in the fibers of that muscle was not found. Several factors indicated that the affected patients had an overall decrease in the total number of muscle cells, perhaps resulting from the expression of genetic defects during embryonic development. This decreased number of muscle cells is an important etiological factor of the non-progressive muscle weakness. There was a marked preponderance of histochemical Type I fibers in the muscle biopsies of the affected patients. Perhaps this represents an abnormality of fiber enzymatic differentiation, a process which also occurs during fetal life.