New mutations in mitochondrial DNA encoded genes of complex I are rarely reported. An infant developed Leigh disease with infantile spasms. Complex I enzyme activity was deficient and response to increasing coenzyme Q concentrations was reduced. Complex I assembly was intact. A new mutation in MT-ND1 m.3928G>C p.V208L, affecting a conserved amino acid in a critical domain, part of the coenzyme Q binding pocket, was present at high heteroplasmy. The unaffected mother did not carry measurable mutant mitochondrial DNA, but concern remained for gonadal mosaicism. Prenatal testing was possible for a subsequent sibling. The ND1 p.V208L mutation causes Leigh disease.
Keywords: Coenzyme Q binding; EEG; Electron transport chain complex 1; HRM; Infantile spasms; LHON; Leber hereditary optic neuropathy; Leigh disease; MELAS; ND1; PAGE; PCR; electroencephalogram; high resolution melt; mitochondrial DNA; mitochondrial encephalomyopathy with lactic acidosis and stroke like episodes; mtDNA; polyacrylamide gel electrophoresis; polymerase chain reaction.