The TWNK (C10orf2) gene encodes Twinkle, an essential helicase for mtDNA replication. Homozygous mutations in TWNK can lead to mitochondrial DNA depletion syndrome 7 (MTDPS7) that usually manifests as Infantile onset spinocerebellar ataxia (IOSCA). Here, we report a 15-year-old Iranian boy with three main symptoms; ataxia, sensorineural hearing loss and optic nerves atrophy which were accompanied by other symptoms including flexion contracture, dysarthric speech, nystagmus, dystonia and borderline intellectual disability. Whole exome sequencing (WES) revealed a homozygous mutation in his TWNK gene. The mutation was a transversion which replaced a C with A (NM_021830.4 (TWNK):c.874C>A). This nucleotide substitution results in replacing a Threonine with Proline in codon 292 of Twinkle protein (p.Pro292Thr). In silico analyses showed that this amino acid change in Twinkle could be deleterious and disease-causing; therefore, we attribute the symptoms of our patient to this mutation. Our study extended the homozygous mutation spectrum of the TWNK gene that leads to IOSCA.