POLG and recessive mitochondrial ataxia syndrome: However, innumerable mutations throughout the POLG gene—even a few heterozygous—cause a variety of phenotypes, including PEO-plus, sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO), mitochondrial recessive ataxia syndrome (MIRAS), and PD, all reviewed by Dr. William Copeland [36].