Drugs, muscle pallor, and pyomyositis

A 33-year-old athletic male was unexpectedly found dead in his bed. For several days prior to his death he complained of tenderness and swelling of his right buttock. The post-mortem examination revealed unilateral pale gluteal muscles and pustular impetiginized skin lesions of the right lower leg. The muscle histology demonstrated pronounced acute inflammation and limited necrosis of muscle fibers confined to the right gluteal muscles. Vascular occlusion and renal abnormalities were excluded by post-mortem angiography and histology respectively, and the diagnosis of non-tropical pyomyositis, possibly originating from the dermatological infection, was made. Toxicological testing revealed a potentially lethal intoxication with fentanyl and morphine. Pyomyositis is etiologically attributed to an infection and predominantly affects large limb or trunk muscles. Males are affected more frequently than females. Histologically, it is dominated by acute inflammatory infiltrates and may lead to sepsis and subsequent death. Although occurring less frequently, pyomyositis must be considered in the differential diagnosis of macroscopic localized muscle pallor, together with vascular occlusion and rhabdomyolysis. In such cases, only the examination of fresh frozen muscle tissue samples from different locations, together with the histological examination of the internal organs, particularly the kidneys, will facilitate the confirmation of the correct diagnosis.