COQ4encodes a structural component of the CoQ10 biosynthesis complex ("complex Q"). Reported variants include missense and loss-of-function alleles, in homozygous or compound heterozygous state. Biochemically, CoQ10 levels in muscle or fibroblasts are decreased in many but not all patients; normal CoQ10 levels in accessible tissues therefore do not exclude the diagnosis. CoQ10-dependent respiratory chain activities (complex II+III) may be reduced. The diagnosis is usually established by gene panel or exome sequencing.
COQ4