Muscle biopsy features in critical ill patients with 2009 influenza A (H1N1) virus infection.

Higher serum creatine kinase (CK) levels in critically ill patients with a confirmed 2009 influenza A (H1N1) infection suggests a possible relationship between the H1N1 virus and muscle tissue. However, there have been no reports with an emphasis on muscle biopsies for patients infected with the H1N1 virus. The objective of this study was to investigate the histological characteristics of the muscle biopsies from critically ill patients with confirmed 2009 H1N1 infections. A series of ten patients with confirmed 2009 H1N1 infection, who presented increased serum CK levels, was analyzed. Histological study found small histochemical alterations in muscles fibers (mainly in NADH, SDH, COX, myophosphorylase, adenylate deaminase and PAS stains), and no histological changes were compatible with inflammatory myopathy. Although our critically ill patients had elevated CK levels, they exhibited few histological/histochemical abnormalities in their muscle biopsy samples; however, those alterations could be consistent with metabolic dysfunction associated with influenza H1N1 infection.