Pipecolic Acid, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Pipecolic acid (PA) is an intermediate of lysine metabolism and is oxidized in the peroxisomes by the enzyme L-pipecolate oxidase. In peroxisome biogenesis disorders (eg, Zellweger syndrome), the activity of this enzyme is lost, resulting in an increase in pipecolic acid levels. In contrast, in peroxisomal disorders involving single enzyme deficiencies such as D-bifunctional protein deficiency, PA is not elevated; therefore PA analysis is useful for differentiating between these 2 groups of disorders.
Increased pipecolic acid levels may also be seen in alpha-aminoadipic semialdehyde dehydrogenase deficiency (pyridoxine dependent epilepsy), hyperlysinemia types 1 and 2, and defects in proline metabolism.
Theoretically, a defect in L-pipecolate oxidase can exist and several cases of hyperpipecolic acidemia have been reported, but a specific enzyme deficiency has not been described in any of the patients.
Differential diagnosis between disorders of peroxisomal biogenesis (eg, Zellweger syndrome) and disorders with loss of a single peroxisomal function
Abnormal elevations of pipecolic acid can be detected in either serum or urine
Elevated pipecolic acid levels are seen in disorders of peroxisomal biogenesis; normal levels are seen in disorders with loss of a single peroxisomal function.
Abnormal levels of pipecolic acid should be interpreted together with the results of other biochemical markers of peroxisomal disorders, such as plasma C22-C26 very long-chain fatty acids, phytanic acid, pristanic acid (POX / Fatty Acid Profile, Peroxisomal (C22-C26), Serum), RBC plasmalogens, and bile acid intermediates.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Newborns with disorders of peroxisomal biogenesis often have normal levels of pipecolic acid which increase with age.
Abnormal results may reflect either prematurity or nongenetic liver and/or renal disease.
Pipecolic acid is not detected by conventional organic acid analysis (OAU / Organic Acids Screen, Urine).
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
<1 month: < or =223.8 nmol/mg creatinine
1-6 months: < or =123.1 nmol/mg creatinine
6 months-<1 year: < or =45.0 nmol/mg creatinine
> or =1 year: < or =5.7 nmol/mg creatinine
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Gould SJ, Raymond GV, Valle D: The peroxisome biogenesis disorders. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, D Valle, et al. New York, McGraw-Hill Book Company, 2001, pp 3181-3217
2. Wanders RJA, Barth PG, Heymans HAS: Single peroxisomal enzyme deficiencies. In The Metabolic and Molecular Bases of Inherited Disease. Eighth edition. Edited by CR Scriver, AL Beaudet, D Valle, et al. New York, McGraw-Hill Book Company, 2001, pp 3247-3248