['To determine the enzymatic defect in a patient with ataxia, dysarthric speech, dry skin, hypotonia, and absent reflexes. The patient was previously diagnosed with a presumed deficiency of trihydroxycholestanoyl-CoA oxidase.', 'Peroxisomes harbor a variety of metabolic functions, including fatty acid beta-oxidation, etherphospholipid biosynthesis, phytanic acid alpha-oxidation, and L-pipecolic acid oxidation. This patient was previously described with an isolated peroxisomal beta-oxidation defect caused by a deficiency of the enzyme trihydroxycholestanoyl-CoA oxidase. This was based on the pattern of accumulating metabolites.', 'Measurement of beta-oxidation enzymes, peroxisomal biochemical analysis in body fluids and cultured skin fibroblasts, and DNA analysis of the PEX12 gene were performed.', 'An isolated beta-oxidation defect in this patient was excluded by measurement of the various beta-oxidation enzymes. The authors found that the patient had a peroxisome biogenesis disorder caused by mutations in the PEX12 gene, although all peroxisomal functions in cultured skin fibroblasts were normal.'] Does reinvestigation of trihydroxycholestanoic acidemia reveal a peroxisome biogenesis disorder?