OPA1 and hereditary optic atrophy: Amongst the published patients with biallelic OPA1 mutations (Additional file 7), the severe neonatal-onset disorder characterized by severe optic atrophy, ataxia, hypotonia, gastrointestinal dysmotility and dysphagia, described in two siblings by Schaaf et al. [5], is the closest to the clinical presentation of P1 and his brother.