Atypical Refsum disease with pipecolic acidemia and abnormal catalase distribution

We describe an 18-year-old patient with psychomotor retardation and abnorma lly short metatarsi and metacarpals but no other signs of classic Refsum di sease. Molecular analysis of the phytanoyl-coenzyme A hydroxylase gene reve aled a homozygous deletion causing a frameshift Surprisingly, L-pipecolic a cid was elevated in plasma, and microscopy of the liver showed a reduced nu mber of peroxisomes per cell and a larger average peroxisome size. These ab normal peroxisomes lacked catalase as did peroxisomes in fibroblasts of thi s patient. Such generalized peroxisomal abnormalities are not present in cl assic Refsum disease.