MT-ND3 and MELAS syndrome: Non-cardiac cause of death were registered in 6 patients; 3 died due to acute respiratory infection (2 diagnosed with MELAS, 1 with tRNAGlu mutation), 2 patients due to acute metabolic crisis, embodying the end-stage of the disease (MT-ND3) or exacerbated by infection (TMEM70); one patient (7.1%) affected by MELAS syndrome died as complication of cerebral stroke.