Test ID: FQPPS    
Porphyrins, Feces

Evaluation of persons who present with signs or symptoms suggestive of porphyria cutanea tarda, hereditary coproporphyria, variegate porphyria, congenital erythropoietic porphyria, or erythropoietic protoporphyria

Specimen submitted must contain at least 100 g of feces. The laboratory may not be able to provide interpretable results for small specimens.

The porphyrias are a group of inborn errors of metabolism resulting from defects in the heme biosynthetic pathway. Enzymatic deficiencies result in the accumulation and excretion of intermediary metabolites in different specimen types. The pattern of excretion of the heme precursors in urine and feces and the accumulation within erythrocytes allow for the detection and differentiation of the hereditary porphyrias. These accumulations cause characteristic clinical manifestations, which may include neurologic and psychological symptoms and/or cutaneous photosensitivity depending upon the specific disorder. Although genetic in nature, environmental factors may exacerbate symptoms, significantly impacting the severity and course of disease. Early diagnosis coupled with education and counseling of the patient regarding the disease and treatment including avoidance of precipitating factors are important for successful management.

Increased fecal porphyrin excretions are observed most commonly in symptomatic patients with congenital erythropoietic porphyria (CEP), porphyria cutanea tarda (PCT), hereditary coproporphyria (HCP), and variegate porphyria (VP). In quiescent phases of VP and HCP, as well as prior to puberty, fecal porphyrin excretion may be within normal limits.

Typically, the work up of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Acute) Testing Algorithm and Porphyria (Cutaneous) Testing Algorithm in Special Instructions or contact Mayo Medical Laboratories to discuss testing strategies. Refer to The Challenges of Testing For and Diagnosing Porphyrias, Mayo Medical Laboratories Communique 2002 Nov;27(11) for more information.

See The Heme Biosynthetic Pathway in Special Instructions.

Abnormal results are reported with a detailed interpretation including an overview of the results and their significance, a correlation to available clinical information provided with the specimen, differential diagnosis, and recommendations for additional testing when indicated and available, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Heme from red meat can contribute to fecal protoporphyrin via action of intestinal microbes and cause a misleading indication of erythropoietic protoporphyria or variegate porphyria.

Aspirin ingestion may cause minimal gastrointestinal bleeding, leading to false elevations of protoporphyrin.

Specimen submitted must contain at least 100 g of feces. The laboratory may not be able to provide interpretable results for small specimens.

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

• The Heme Biosynthetic Pathway
• Stool Collection Information Sheet
• Informed Consent for Genetic Testing
• Porphyria (Acute) Testing Algorithm
• Porphyria (Cutaneous) Testing Algorithm