Failure to over express MHC-CLASS-1 on muscle biopsy in a case of amyopathic juvenile dermatomyositis

The concept of amyopathic dermatomyositis or dermatomyositis sine myositis, is contentious, particularly within paediatrics. We report an 8-year-old girl presenting with dermatological dermatomyositis without muscle weakness. Muscle biopsy changes are described, in particular, the absence of MHC class 1 over expression. This supports the concept of amyopathic dermatomyositis as a subgroup of juvenile dermatomyositis (JDM) and suggests that immunohistological analysis may be a valuable in excluding a myositic element in such cases.