MORC3 and dermatomyositis: Five mutually exclusive MSAs have been associated with DM: anti-Mi2, anti-melanoma differentiation-associated protein 5 (MDA5), anti-nuclear matrix protein-2 (NXP2), anti-transcriptional intermediary factor-1-γ (TIF-1-gamma), and anti-small ubiquitin-like modifier-activating enzyme (SAE).