Familial dermatomyositis.

Susceptibility, response to therapy, prognosis, and natural history of connective tissue diseases are variably linked to histocompatibility antigens (HLA), although the precise role that such genes play is still not clear. In juvenile dermatomyositis (JDMS) there are few reports of both concordance and discordance in identical twins and occurrence in more than one family member. To further document the familial occurrence of JDMS, we describe 2 sisters, one with classical JDMS and the other with amyopathic dermatomyositis. The 2 patients were shown to share the HLA-DQA1*0501 allele, known to be associated with susceptibility to JDMS.