Tubular cytoplasmic inclusions in a case of childhood dermatomyositis with migratory subcutaneous nodules.

A boy with dermatomyositis which began at the age of one year and five months showed multiple migratory subcutaneous nodules, which have seldom been described. Histological and electron microscopic studies of muscles and subcutaneous nodules demonstrated the following interesting findings. 1. Light microscopy. The migratory subcutaneous nodules consisted of non-suppurative panniculitis and ischaemic adipo-necrosis as a sequel to vascular lesions. This finding suggests that the nodules may have arisen from the subcutaneous adipose tissue which had been severely damaged by systemic angiopathy. 2. Electron microscopy. Examination of the vessels in muscle and subcutaneous nodules showed tubular cytoplasmic inclusions with a diameter of approximately 250 A in the endoplasmic reticulum of vascular endothelial cells. These observations provide strong support for the concept that the fundamental pathologic process in childhood dermatomyositis is of a vascular nature, and the primary lesion is in the walls of the intramuscular blood vessels.