Atypical refsum disease with pipecolic acidemia and abnormal catalase distribution

We describe an 18-year-old patient with psychomotor retardation and abnormally short metatarsi and metacarpals but no other signs of classic Refsum disease. Molecular analysis of the phytanoyl-coenzyme A hydroxylase gene revealed a homozygous deletion causing a frameshift. Surprisingly, L-pipecolic acid was elevated in plasma, and microscopy of the liver showed a reduced number of peroxisomes per cell and a larger average peroxisome size. These abnormal peroxisomes lacked catalase as did peroxisomes in fibroblasts of this patient. Such generalized peroxisomal abnormalities are not present in classic Refsum disease.