Fig. 18

Gain-of-function mutations in MDA5 or RIG-I in patients with Singleton-Merten syndrome (SMS). Typical SMS is caused by gain-of-function mutations in MDA5. Atypical SMS is caused by gain-of-function mutations in RIG-I. Gain-of-function mutations of MDA5 and RIG-I lead to constitutive activation of type I IFN signaling pathways