Novel NDUFS4 gene mutation in an atypical late-onset mitochondrial form of multifocal dystonia

Mitochondrial complex I, the largest component of the mitochondrial respiratory chain, comprises 44 subunits of which 7 are encoded by the mitochondrial genome and the remainder by the nuclear genome.1 Isolated complex I deficiencies represent a major contribution within the group of respiratory chain defects.2 We report an atypical case carrying a homozygous NDUFS4 missense mutation, with late-onset multifocal dystonia, in contrast to expected clinical phenotypes due to other NDUFS4 mutations, which have been constantly reported to be responsible for Leigh syndrome of early onset and death.3