Hereditary coproporphyria

Hereditary coproporphyria (HCP) is a form of hepatic porphyria associated with a deficiency of the enzyme coproporphyrinogen III oxidase.

Hereditary coproporphyria (HCP) is a hereditary genetic disease that causes purple urine, photo sensitivity , and attacks of abdominal pain. Symptoms vary from mild to severe and can be regulated with diet and triggered with drug use.

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Symptoms

The primary symptom is a condition known as prophyria. Those afflicted suffer a range of symptoms including reddish-purple urine, light sensitivity of the skin, and attacks of acute abdominal/nerve pain. These symptoms manifest themselves differently in patients but can be triggered by infections, hormonal changes, or dieting. The use of alcohol and certain drugs such as barbiturates and birth control pills can also cause these attacks (Medicinenet.com).

Function

The coproporphinogen oxidase gene is a enzyme that converts coproporphyrinogen III to protoporphyrinogen IX (OMIM). Heme is made from porphyrin and when a mutation occurs, heme production is interrupted. This leads to an overabundance of porphyrin in the body, which then exits through urine/feces (MedicineNet.com).

Pathophysiology

Hereditary coproporphyria is the result of a point mutation in the coproporphinogen oxidase (CPO) gene (OMIM). Documented changes in the DNA sequence that cause HCP include missense, nonsense, deletion and splicing of single nucleotides (OMIM). Documented changes in the protein sequence have been a replacement of ser208 to phe(s208f) and arg328 to cys(r328c) (OMIM). Aside from varying intensity of symptoms there are no other known mutations, and it is not known at this time if mutations in other genes can trigger this same disease. At this time it is not known if there are any specific groups of people that are especially susceptable to this disease, as patients have been documented all over the world.

Molecular Biology

The CPO gene is located in chromosome 3 on the q12 locus (OMIM). The gene is 14,000 bases in length, has 6 introns, and 7 exons. Once the introns are spliced out the actual coded mRNA is only 2675 bases in length (genbank). The protein contains 323 amino acids.

Heredity

HCP is an autosomal disease, meaning it is carried in one of the non-sex chromosomes(OMIM). It is unclear at this time if the disease inheritance is dominant or recessive. There have been documented cases of both heterozygous and homozygous inheritance, with similar symptoms in each patient (OMIM).

Treatment

While there is no cure for this condition, there are preventative measures people can take to regulate symptoms. A diet high in carbohydrates, as well as avoidance of aggravating factors (such as alcohol and drug use) can prevent attacks (MediciNet.com).

References

1. Coproporphyria. Online Mendelian Inheritance In Man (OMIM). Retrieved on 2007-12-07. http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=121300

2. Coproporphyrinogen Oxidase. GenBank. Retrieved on 2007-12-07. http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?db=nucleotide&val=33991442

3. Porphyria. MedicineNet.com. Retrieved on 2007-12-07. http://www.medterms.com/script/main/art.asp?articlekey=10360