Perivascular siderophages in skeletal muscle from a patient with diabetic neuropathy.

Hemosiderin deposition in skeletal muscle histiocytes is uncommon but has been occasionally noted in hemochromatosis, hemosiderosis and Waldenstrom's macroglobulinemia. The purpose of this report is to describe the light microscopic and ultrastructural characterization of this abnormality in a patient with diabetes mellitus. A 56-year-old diabetic male presented with paresthesias and intermittent diffuse lower extremity myalgias. Neurologic examination was remarkable only for diminished vibratory sense in the toes, diminished deep tendon reflexes, and ankle-level stocking distribution hypalgesia. There was no clinical evidence of hemochromatosis and laboratory studies ruled out Waldenstrom's macroglobulinemia. Muscle biopsy showed modest variability in myofiber diameter with a few scattered angular atrophic type II fibers. There were numerous collections of granular pigment-containing histiocytes in endomysial and perimysial perivascular areas and marked thickening of blood vessels walls. The histiocytic pigment was bright blue with the Prussian blue stain. No pigment was seen in the myofibers. Ultrastructural examination revealed numerous perivascular histiocytes filled with hemosiderin containing granules of variable size and density and marked thickening of capillary walls with striking reduplication of basement membranes. A modest number of subsarcolemmal paracrystalline mitochondrial inclusions were present. X-ray dispersion analysis of the histiocytic pigment material confirmed the presence of iron in the lysosomal granules.