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counseling of the patient regarding the disease and treatment including avoidance of precipitating factors
are important for successful management. Urinary porphyrin determination is helpful in the diagnosis of
most porphyrias including congenital erythropoietic porphyria (CEP), porphyria cutanea tarda (PCT),
acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). In
addition, measurement of porphobilinogen (PBG) in urine is important in establishing the diagnosis of the
acute neurologic porphyrias (AIP, HCP and VP). Neither urine porphyrins nor PBG is helpful in
evaluating patients suspected of having erythropoietic protoporphyria (EPP). Historically, the porphyrias
have been divided into 2 groups, erythropoietic and hepatic based on the major site of substrate
accumulation and/or overproduction. Another classification is based on clinical presentation and divides
the porphyrias into acute or nonacute (cutaneous) categories. The acute porphyrias include AIP, HCP and
VP. The nonacute porphyrias include CEP, PCT and EPP. PCT is the most common form of porphyria. It
presents clinically with increased skin fragility and the formation of vesicles and bullae on sun-exposed
areas of the skin. PCT can be either sporadic (acquired) or inherited in an autosomal dominant manner. A
biochemical diagnosis of PCT is characterized by increased urinary excretion of uroporphyrin and
heptacarboxylporphyrin. Lesser amounts of hexacarboxyl-, pentacarboxyl- and coproporphyrin may also
be excreted. Hepatoerythropoietic porphyria (HEP) is observed when an individual inherits PCT from
both parents. Patients exhibit a similar porphyrin excretion pattern as PCT although the clinical
presentation is similar to what is seen in CEP. The clinical features of the acute porphyrias include
abdominal pain, sensory neuropathy, and psychosis. Photosensitivity is not associated with AIP but may
be present in HCP and VP. The biochemical diagnosis of AIP is based upon an increased urinary
excretion of PBG and aminolevulinic acid (ALA). In addition, uroporphyrin is also usually increased. A
urine specimen obtained during an acute episode is most informative, as these analytes may be normal or
only slightly increased between acute episodes of AIP. With respect to HCP and VP, the excretion pattern
observed in urine is indistinguishable from one another with elevations of both coproporphyrin and PBG
excretion being observed in urine. Fecal porphyrins analysis is recommended to differentiate VP from
HCP. CEP is a rare disorder typically presenting in childhood with prominent photosensitivity and
voiding of dark, wine-colored urine. A few milder adult-onset cases have been documented as well as
cases that are secondary to myeloid malignancies. A biochemical diagnosis of CEP is characterized by
increased urinary excretion of uroporphyrin and coproporphyrin with the excretion of uroporphyrin
usually exceeding that of coproporphyrin and the series I isomers predominating. Lesser amounts of the
heptacarboxyl-, hexacarboxyl-, and pentacarboxyl porphyrins may be excreted. The urinary excretion of
ALA and PBG is usually within normal limits. In addition to being a sign of an inheritable problem,
porphyrinuria may result from exposure to certain drugs and toxins or other medical conditions (ie, renal
disease, hereditary tyrosinemia type I). Heavy metals, halogenated solvents, various drugs, insecticides,
and herbicides can interfere with heme production and cause "intoxication porphyria." Chemically, the
intoxication porphyrias are characterized by increased excretion of ALA, PBG, uroporphyrin and/or
coproporphyrin in urine. Typically, the workup 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.
Useful For: Preferred test during symptomatic periods for acute intermittent porphyria, hereditary
coproporphyria, and variegate porphyria Preferred test to begin assessment for congenital erythropoietic
porphyria and porphyria cutanea tarda
Interpretation: 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.
Reference Values:
UROPORPHYRINS (octacarboxyl)
< or =30 nmol/L
HEPTACARBOXYLPORPHYRINS
< or =7 nmol/L
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 1450