A case series of Cypriot patients with CblC defect: Clinical, biochemical and molecular characteristics

Methylmalonic aciduria and homocystinuria, CblC type, is an inborn error of intracellular vitamin B12 (cobalamin) metabolism caused, in the majority of cases, by mutations in the MMACHC gene. Five Cypriot patients (four males and one female) were diagnosed with a CblC defect. Age at diagnosis ranged from 10 days to 9 months. We present here the clinical, biochemical and molecular findings of these patients. Our retrospective study indicates that all patients were carriers of the known p.Arg91LysfsTer14 variant in either a homozygous or compound heterozygous state with other known MMACHC pathogenic variants. Out of three patients sharing the same genotype the one diagnosed and initiated treatment in the neonatal period displayed an improved clinical outcome.