In one reported case, a 41-year-old woman developed scaly erythematous lesions on her hands, elbows and knees and symmetric polyarthritis; this was initially diagnosed and treated as psoriatic arthritis, only to later be recognized as anti-MDA5 positive dermatomyositis when muscle weakness, rash distribution, and specific antibodies declared themselves (30). The gene discussed is IFIH1; the disease is psoriatic arthritis.