The biochemical and clinical diagnostic characteristics of peroxisomal disorders are reviewed by authors from the Department of Pediatrics, Medical University of South Carolina, Charleston, SC. Two major groups are recognized: 1) those that represent a diffuse peroxisomal dysfunction due to (a) a reduction in number of peroxisomes (Zellweger’s syndrome, neonatal adrenoleukodystrophy, infantile Refsum’s disease, and hyperpipecolic acidemia); and (b) normal numbers but reduced activities of multiple enzymes (rhizomelic chondrodysplasia punctata); and 2) those disorders with specific single peroxisomal enzymatic defects (childhood adrenoleukodystrophy-X-linked, adult Refsum’s disease, hyperoxaluria, acatalasemia, and pseudo-Zellweger’s syndrome).
Peroxisomal disorders should be considered in any infant with hypotonia and delays in psychomotor development, and especially in those with facial dysmorphisms (high and prominent forehead), hepatomegaly, cataracts, retinitis, calcific stippling, short limbs, failure to thrive, seizures, and hearing deficit. In childhood, loss of motor skills, progressive dementia, and skin bronzing should suggest the diagnosis. Measurement of very long chain fatty acids is used to confirm the biochemical defect, and other tests including bile acid, phytanic acid, and plasmalogen are included for specific diagnoses. 
COMMENT. Peroxisomal disorders are rare but important because clinical sequelae can be related to specific biochemical deficits and some may be identified prenatally and their recurrence prevented. Dietary restriction of very long chain fatty acids and plasmapheresis are helpful in treatment by controlling the accumulation of toxic metabolites in some peroxisomal disorders, and the addition of glycerol trioleate, a lipid containing unsaturated fatty acid, is a promising new therapy that reduces the synthesis of C22-26 fatty acids. For further information on peroxisomal disorders, refer to a special article by . A family with Refsum’s disease (heredopathia atactica polyneuritiformis) in whom 4 out of 6 siblings were affected is reported from the Department of Neurology, Westminster Hospital, London  Retinitis pigmentosa was the presenting diagnostic sign in the index case, and other affected members of the family were detected by screening for raised plasma phytanic acid levels. Early diagnosis is important because dietary treatment will prevent the development of neuropathy, ataxia, cardiac arrhythmias, and ichthyosis. Retinitis pigmentosa, anosmia, and ataxia should suggest the diagnosis.