Anti‐TIF‐1β antibody in dermatomyositis.

Summary: Dermatomyositis is a disease where skin and muscles become inflamed. Sometimes it affects just muscles, sometimes just the skin. Most patients fall within a spectrum where both are inflamed. Elevations of the enzyme creatinine kinase (CK) are found in the bloodstream if muscles are inflamed, and tests such as an electromyogram may also be abnormal. Dermatomyositis is an autoimmune condition, with antibodies directed against the patient's own tissues (autoantibodies). Different patterns of such autoantibodies are associated with different subsets of the condition. There is also an underlying cancer in a minority of adults with dermatomyositis. One group of autoantibodies is specifically associated with muscle inflammation. Within it is a family called anti‐TIF (transcriptional intermediary factor) antibodies, including anti‐TIF‐1α and ‐1γ antibodies. Anti‐TIF‐1α antibodies always appear with anti‐TIF‐1γ. In this paper from Japan, the authors investigate which conditions result when patients have a third autoantibody, anti‐TIF‐1β, on its own, without either of the other two. From 3442 stored serum (blood) samples from patients with connective tissue diseases, they found seven such patients. Six had dermatomyositis, but in two, muscles were either not involved (one patient) or involved but producing no symptoms (one patient); the other four patients had classic dermatomyositis but muscle involvement was mild and only one of the four had an elevated CK. One of these four patients did, however, have an underlying cancer. The seventh patient had 'undifferentiated connective tissue disease'. The authors conclude that anti‐TIF‐1β antibodies are associated with dermatomyositis where muscle inflammation is absent or only mild. Linked Article: Ueda‐Hayakawa et al. Br J Dermatol 2019; 180:881–887 [ABSTRACT FROM AUTHOR]