Dermatomyositis in a donor and receptor of allogenic hematopoietic stem cell transplantation: Auto- or alloimmune disease?

We present the case of a 63-year-old woman who developed dermatomyositis after hematopoietic stem cell transplantation. Anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibodies were positive and pulmonary involvement was severe and progressive. In addition, we also report that the patient's sister and donor also developed dermatomyositis. She had positive anti-PL7 antibodies and negative anti-MDA5 antibodies. The occurrence of autoimmune diseases after allogeneic hematopoietic stem cell transplantation is infrequent and difficult to interpret due to the reconstitution of the immune system and the multifactorial origin of most of these diseases. To our knowledge, this is the first described case of a hematopoietic progenitor transplant donor and recipient developing dermatomyositis. These findings make us wonder whether the dermatomyositis in this case is due to a shared genetic predisposition or to the donor's disease developing in the recipient.