Hepatic peroxisomes in isolated hyperpipecolic acidaemia: evidence supporting its classification as a single peroxisomal enzyme deficiency

Hyperpipecolic acidaemia is still regarded as a peroxisomal assembly defici ency. The enzyme responsible for the accumulation of pipecolic acid is loca ted in the peroxisomes in man. We studied the appearance and alterations of peroxisomes in liver biopsy material from three unrelated children sufferi ng from isolated hyperpipecolic acidaemia, in which only the metabolism of pipecolic acid is disturbed, using light and electron microscopy after cyto chemical staining for visualisation of peroxisomes. Morphometric results sh owed the presence of normal-sized to small peroxisomes, an increase in numb er and abnormally shaped organelles, suggesting enhancement of metabolic ef ficiency. In one case enlarged organelles were observed. Skin fibroblasts w ere studied in all patients: their peroxisomes appeared to be normal. The o bvious presence of peroxisomes in isolated HPA indicates that this disorder should be classified as a single peroxisomal enzyme deficiency.