AbstractCylindrical spirals are abnormal uniform membranous inclusions in skeletal muscle, usually confined to type 2 fibers. Hitherto, only five cases have been published with various clinical syndromes. Here, a case is presented for the first time with detailed electrophysiological, histometrical, and biochemical analysis: a 60‐year‐old man with slowly progressing polyneuropathy confirmed by electrophysiological findings, and a history of diabetes, alcoholism, nicotine abuse, and weight reduction. In various muscle biopsies, large aggregates of cylindrical spirals were found almost exclusively in type 2B fibers. Obviously, the aggregates were derived from abnormal perinuclear and, therefore, mainly subsarcolemmal tubulovesicular structures. Morphometrical, histochemical, and biochemical analysis of muscle revealed no further information about the nature of these inclusions. They were not present in skin biopsy containing subcutaneous ner