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Test ID: CPOXZ CPOX Gene, Full Gene Analysis

Useful For

Confirmation of hereditary coproporphyria (HCP) for patients with clinical features

 

This test should be ordered only for individuals with symptoms suggestive of HCP. Asymptomatic patients with a family history of HCP should not be tested until a mutation has been identified in an affected family member.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
CULFB Fibroblast Culture for Genetic Test Yes No

Testing Algorithm

If skin biopsy is received, fibroblast culture for genetic test will be added and charged separately.

Method Name

Polymerase Chain Reaction (PCR) Amplification/DNA Sequencing

Reporting Name

CPOX Gene, Full Gene Analysis

Specimen Type

Varies


Specimen Required


Specimen preferred to arrive within 96 hours of collection.

 

Submit only 1 of the following specimens:

 

Preferred:

Specimen Type: Whole blood

Container/Tube:

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated

 

Specimen Type: Cultured fibroblasts

Container/Tube: T-75 or T-25 flask

Specimen Volume: 1 full T-75 or 2 full T-25 flasks

Specimen Stability Information: Ambient (preferred)/Refrigerated <24 hours

 

Specimen Type: Skin biopsy

Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [T115]).

Specimen Volume: 4-mm punch

Specimen Stability Information: Refrigerated (preferred)/Ambient

 

Acceptable:

Specimen Type: Blood spot

Container/Tube: Whatman Protein Saver 903 Paper

Specimen Volume: 5 blood spots

Collection Instructions:

1. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.

2. Do not expose specimen to heat or direct sunlight.

3. Do not stack wet specimens.

4. Keep specimen dry.

Specimen Stability Information: Ambient (preferred)/Refrigerated


Specimen Minimum Volume

Blood: 1 mL/Blood Spots: 3

Specimen Stability Information

Specimen Type Temperature Time
Varies Varies

Clinical Information

Hereditary coproporphyria (HCP) is an autosomal dominant (AD) acute hepatic porphyria that presents with clinical attacks of neurologic dysfunction, commonly characterized as abdominal pain. However, these acute attacks are variable and can include vomiting, diarrhea, constipation, urinary retention, acute episodes of neuropathic symptoms, psychiatric symptoms, seizures, respiratory paralysis, tachycardia, and hypertension. Respiratory paralysis can progress to coma and death. HCP is also associated with cutaneous manifestations, including edema, sun-induced erythema, acute painful photodermatitis, and urticaria. In some cases, patients present with isolated photosensitivity.

 

HCP is caused by AD mutations in the CPOX gene. Mutations may have incomplete penetrance. Homozygous mutations in CPOX have been reported in association with a more severe, phenotypically distinct condition called harderoporphyria that is characterized by neonatal hemolytic anemia with mild residual anemia during childhood and adulthood. Affected patients may also present with skin lesions and fecal harderoporphyin accumulation may be observed. This condition is inherited in an autosomal recessive pattern and all patients identified to date have been heterozygous or homozygous for the K404E mutation.

 

For HCP, acute attacks may be prevented by avoiding both endogenous and exogenous triggers. These triggers include porphyrogenic drugs, hormonal contraceptives, fasting, alcohol, tobacco, and cannabis.

 

Fecal porphyrins analysis and quantitative urinary porphyrins analysis are helpful in distinguishing HCP from other forms of acute porphyria.

Reference Values

An interpretive report will be provided.

Interpretation

All detected alterations are evaluated according to American College of Medical Genetics recommendations.(1) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Clinical Reference

1. Richards S, Aziz N, Bale S, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med 2015 May;17(5):405-424

2. Siegesmund M, van Tuyll van Serooskerken AM, Poblete-Gutierrez P, et al: The acute hepatic porphyrias: current status and future challenges. Best Pract Res Clin Gastroenterol 2010 Oct;24(5):593-605

3. Anderson KE, Bloomer JR, Bonkovsky HL, et al: Recommendations for the diagnosis and treatment of the acute porphyrias. Ann Intern Med 2005 Mar 15;142(6):439-450

4. Schmitt, C, Gouya L, Malonova E, et al: Mutations in human CPO gene predict clinical expression of either hereditary coproporphyria or erythropoietic harderoporphyria. Hum Mol Genet 2005;14(20):3089-3098

Day(s) and Time(s) Performed

Performed weekly, Varies

Analytic Time

14 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81405-CPOX

81479-Unlisted molecular pathology procedure

Fibroblast Culture for Genetic Test

88233-Tissue culture, skin or solid tissue biopsy (if appropriate)

88240-Cryopreservation (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CPOXZ CPOX Gene, Full Gene Analysis In Process

 

Result ID Test Result Name Result LOINC Value
52457 Result Summary 50397-9
52458 Result In Process
52459 Interpretation In Process
52460 Additional Information 48767-8
52461 Specimen 31208-2
52462 Source 31208-2
52463 Released By No LOINC Needed

Forms

1. Molecular Genetics: Biochemical Disorders Patient Information (T527).

2. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-inherited-molecular