Brown-Vialetto-Van Laere syndrome associated with SLC52A2 mutations is inherited as an autosomal recessive condition (Fig. 6), which helps to differentiate it from other optico-acoustic neuropathies including autosomal dominantly inherited OPA1 or MFN2 mutations, X-linked PRPS1 mutations and mitochondrially inherited neuropathy caused by mitochondrial DNA mutations (such as Leber’s hereditary optic neuropathy or the syndrome of neuropathy, ataxia and retinitis pigmentosa known as ‘NARP’). The gene discussed is MFN2; the disease is Down syndrome.