The most frequent genes were those associated with spastic ataxia, ataxia, and neuropathy or AOA: SACS (4 families, 21.1%), KIF1C (2 families, 10.5%), and PNKP (3 families, 15.8%); the remaining genes were identified in single families only. The gene discussed is PNKP; the disease is spastic ataxia.