The main clinical features of the 11 AOA-affected persons (four males and seven females) who were found to have PNKP mutations are presented in Table 1. All of them were either homozygotes or compound heterozygotes for PNKP mutations (Table 2 and Figure 1). Age at onset ranged from 1 to 9 years; the mean was 4.3 ± 2.3 years. Most individuals exhibited dystonia as their first symptom; this was so prominent that many of these individuals underwent diagnostic procedures for extrapyramidal disorders. In all cases, dystonia spontaneously attenuated during the course of the disease. The second most common symptom was ataxia, followed by oculomotor apraxia. All individuals had signs of polyneuropathy with early, generalized areflexia. Distal-muscle wasting and weakness led to tetraplegia and short atrophic hands and feet. Loss of the ability to walk occurred 7–21 years after disease onset, and most individuals were wheelchair bound by adolescence. Cognitive impairment was present in seven persons, two of whom were severely demented. Alpha-fetoprotein, albumin, and cholesterol levels were highly variable in this cohort; alpha-fetoprotein levels were increased in five individuals, albumin was decreased in six, and cholesterol was elevated in five cases, all of which was determined at later stages of disease progression. In all 11 individuals, brain MRIs revealed cerebellar atrophy.