The second common POLG mutation, p.W748S, usually found in cis with p.E1143G, has been identified in the homozygous state or compound heterozygous with other POLG mutations in patients with various clinical manifestations including early onset Alpers disease, PEO, ataxia, sensory neuropathy, PEO, and dysphagia (http://tools.niehs.nih.gov/polg). The gene discussed is POLG; the disease is cerebellar ataxia.