POLG and cerebellar ataxia: On the other hand, dominant mutations in POLG1 are usually associated with adult-onset progressive external ophthalmoplegia phenotypes and variable neurological manifestations such as cerebellar ataxia, extrapyramidal signs, peripheral neuropathy, mental retardation, hypogonadism, and gastrointestinal motility disorders [41, 45, 46, 47].