A polymorphism in c.14576G>A in RNF213 was identified in 95% of familial patients with MMD and 79% of sporadic cases, and RNF213 was found to correlate with the early onset and severe forms of MMD, indicating its value as a good biomarker for predicting prognosis [12]. The gene discussed is RNF213; the disease is multiminicore myopathy.