These included 2 cases (18.2%, n = 2/11) of methylmalonic encephalopathy followed by 1 case (9.1%, n = 1/11) each of carnitine acylcarnitine translocase deficiency, Hartnup disorder, HMG-CoA lyase deficiency, HMG-CoA synthase-2 deficiency, maple syrup urine disease type IA, methylmalonic aciduria, methylmalonic aciduria type mut (0), ornithine transcarbamylase deficiency, and tyrosinemia type 1, respectively (Additional file 3). Here, HMGCS2 is linked to vitamin B12-unresponsive methylmalonic acidemia type mut-.