Adult Cerebellar Ataxia, Axonal Neuropathy, and Sensory Impairments Caused by Biallelic SCO2 Variants

SCO2 encodes a 266-amino-acid metallochaperone involved in copper supply for the assembly of cytochrome c oxidase or complex IV (CIV). CIV is the terminal enzyme of the energy-transducing respiratory chain that transfers electrons from reduced cytochrome c to oxygen via 3 copper ions.1 SCO2 pathogenic variants were first identified in children with hypertrophic cardiomyopathy, often associated with developmental delay and lactic acidosis2 (Figure, A). SCO2 variants were then reported in children with Leigh syndrome3 and early-onset axonal neuropathy,4 possibly associated with cerebellar ataxia5 (Figure, A). Here, we report heterozygous missense SCO2 variants in a 48-year-old patient presenting with a complex neurologic and sensory phenotype comprising cerebellar ataxia, sensory neuronopathy, deafness, pigmentary retinopathy, and cataract. The authors thank Sandrine Filaut et Laura Legrand for their help with NGS.