Scientific Aspects and Clinical Signs of Muscle Pain

Abstract

SUMMARYObjectives: The clinically most important painful muscle disorders are inflammatory and metabolic myopathies. In the three major groups of autoimmune inflammatory myopathies, dermatomyositis, polymyositis, and sporadic inclusion body myositis, muscle pain is most frequent in dermatomyositis and almost absent in sporadic inclusion body myositis.Findings: The myopathological feature of dermatomyositis is polymyositis of the perifascicular type with pronounced inflammatory reaction of small blood vessels with C5B9 complement deposits and tubuloreticular inclusions as seen by electron microscopy. The last mentioned structures are induced by cytokines. Small free nerve endings are always connected to small blood vessels. In dermatomyositis one can show very clearly that substance P and calcitonine gene related peptide are elevated as signs of an increased nociceptive input. In polymyositis and especially inclusion body myositis there is no such muscular pathology and as far as examined no elevation of s...