Ataxia due to Refsum disease

**Definition:** Ataxia in the setting of Refsum disease, a rare autosomal recessive disorder caused by a mutation in the PHYH gene coding for peroxisomal phytanoyl-CoA hydroxylase or PEX7, coding for peroxin 7 receptor protein. Onset is usually in late childhood, initially presenting with retinitis pigmentosa, with progression to ataxia and chronic polyneuropathy.