Peroxisomal Disorders
Plasma very long chain fatty acid analysis remains the most useful screening test for these conditions. VLCFA concentrations are significantly increased in general peroxisomal disorders such as Zellweger syndrome as well as in rare peroxisomal-oxidation disorders. In X-linked adrenoleukodystrophy the C26/C22 ratio is less markedly raised. Where disorders such as Zellweger are strongly suspected it is important to also request plasmalogens on erythrocytes. Fibroblast assays may be required to confirm the diagnosis. Please note that phytanic acid levels will only be abnormally raised after sufficient dietary intake i.e. older patients.
| Test | Required specimen & volume | Special precautions | Turnaround time | Reference ranges | Section |
|---|---|---|---|---|---|
|
Very Long Chain Fatty Acids General peroxisomal disorders, VLCFA oxidation defects and X-linked ALD |
5ml EDTA or 2ml P | To reach the laboratory within 72 hours | 4 working weeks |
C26 / C22 < 0.033 C24 / C22 0.65 – 1.05 |
Metabolites |
|
Phytanic and Pristinic acids Refsum disease, RCDP and other peroxisomal disorders |
5ml EDTA or 2ml P | To reach the laboratory within 72 hours | 4 working weeks | < 16µmol/L | Metabolites |
|
Plasmalogens RCDP and general peroxisomal disorders |
5ml EDTA | To reach the laboratory within 72 hours | 4 working weeks | Reference values quoted | Metabolites |