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PEWE
31893
has additional questions.
Reference Values:
< or =1.3 mcmol/L
Clinical References: 1. Tortorelli S, Kloke K, Raymond K: Chapter 15: Disorders of porphyrin
metabolism. In Biochemical and Molecular Basis of Pediatric Disease. Fourth edition. Edited by DJ
Dietzen, MJ Bennett, ECC Wong. AACC Press, 2010, pp 307-324 2. Nuttall KL, Klee GG: Analytes of
hemoglobin metabolism - porphyrins, iron, and bilirubin. In Tietz Textbook of Clinical Chemistry. Fifth
edition. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 2001, pp 584-607 3.
Anderson KE, Sassa S, Bishop DF, Desnick RJ: Disorders of heme biosynthesis: X-linked sideroblastic
anemia and the porphyrias. In The Metabolic Basis of Inherited Disease. Eighth edition. Edited by CR
Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill BookCompany, 2001, pp 2991-3062
Porphyrins Evaluation, Washed Erythrocytes
Clinical Information: The porphyrias are a group of inherited disorders resulting from an enzyme
deficiency in the heme biosynthetic pathway. Depending on which enzyme is deficient, various
porphyrins and their precursors accumulate in plasma, erythrocytes, and tissues, and are excreted in the
urine, feces, or both. The porphyrias can be classified as either erythropoietic or hepatic. Both the
erythropoietic porphyrias and the chronic hepatic porphyrias are associated with cutaneous
photosensitivity, but not with the neurological symptoms that accompany the acute hepatic porphyrias.
Diagnosis of the erythropoietic porphyrias (ie, erythropoietic protoporphyria [EPP] and congenital
erythropoietic porphyria [CEP]) can be determined by analysis of porphyrins in the erythrocytes.
Erythrocyte (RBC) porphyrins consist almost entirely of protoporphyrin. Increased RBC protoporphyrin
is characteristic of EPP and of the intoxication porphyrias that may be caused by heavy metals,
halogenated solvents, some pesticides, and medications. However, iron deficiency anemia is the most
common cause of increased RBC protoporphyrin. Therefore, when total RBC porphyrins are elevated,
fractionation and quantitation of zinc-complexed and noncomplexed (free) protoporphyrin are necessary
to differentiate the inherited porphyrias from other causes of elevated porphyrin levels. Zinc-complexed
protoporphyrin may be increased in RBCs in association with: -Iron-deficiency anemia (the most common
cause of elevated zinc protoporphyrin) -Chronic intoxication by heavy metals (primarily lead) or various
organic chemicals -CEP -Hepatoerythropoietic porphyria, a rare form of porphyria caused by homozygous
or compound heterozygous mutations in the uroporphyrinogen decarboxylase gene (UROD) Free
protoporphyrin is increased in RBCs in association with EPP, an erythropoietic porphyria that is inherited
in an autosomal dominant fashion. EPP is considered to be the third most common form of porphyria. It is
caused by diminished ferrochelatase activity, which results in increased free protoporphyrin levels in
RBCs, plasma, and feces. Onset of symptoms typically occurs in childhood with cutaneous
photosensitivity in sun-exposed areas of the skin, generally becoming worse in the spring and summer
months. Common symptoms may include itching, edema, erythema, stinging or burning sensations, and
occasionally scarring of the skin in sun-exposed areas. CEP is an erythropoietic porphyria that is inherited
in an autosomal recessive fashion. CEP is caused by uroporphyrinogen III synthase deficiency, which
results in the accumulation and excretion of uroporphyrin I and coproporphyrin I in urine and feces.
Circulating RBCs contain measurable amounts of uroporphyrin and coproporphyrin. RBC zinc
protoporphyrin may also be elevated due to increased erythropoiesis. Symptoms typically present in early
infancy with red-brown staining of diapers, severe cutaneous photosensitivity with fluid-filled bullae and
vesicles. Other common symptoms may include thickening of the skin, hypo- and hyperpigmentation,
hypertrichosis, cutaneous scarring, and deformities of the fingers, eyelids, lips, nose, and ears.
Useful For: Diagnosis of erythropoietic protoporphyria and congenital erythropoietic porphyria
Evaluation of chronic intoxication from exposure to a variety of agents including heavy metals and
chemicals Differentiating iron-deficiency anemia from other causes of elevated porphyrin levels There are
2 test options: PEE/88886 Porphyrins Evaluation, Whole Blood and PEWE/31893 Porphyrins Evaluation,
Washed Erythrocytes. The whole blood option is easiest for clients but requires that the specimen arrive at
Mayo Medical Laboratories within 48 hours of draw. When this cannot be ensured, washed RBCs should
be submitted.
Interpretation: An elevation of total RBC porphyrins can be an expression of a primary or secondary
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