Learn More - Overview of the Porphyrias
The Acute Porphyrias:
Four of the porphyrias cause acute neurological symptoms. They are not common and may be difficult to diagnose. It is estimated that about 1 in 10,000 Europeans or people of European ancestry carries a mutation in one of the genes for acute porphyria, although mutations have been found in all races and many other ethnicities.
Hereditary Coproporphyria (HCP)
What is Hereditary Coproporphyria?
The incidence of HCP appears to be at most 2 per 1,000,000. HCP is due to a mutation, or change, in, a person’s CPOX gene. It is an autosomal dominant disorder, meaning that a person needs a mutation on only one of his / her CPOX genes to have HCP.
Who gets Hereditary Coproporphyria?
HCP results from a mutation in the gene for the enzyme coproporphyrinogen oxidase (CPOX). Other activating factors, such as drugs, hormones, and dietary changes, must be present. Sometimes, activating factors cannot be identified.
Acute attacks are often provoked by drugs such as barbiturates, sulfonamide antibiotics, anti-seizure drugs, rifampin, metoclopramide, and alcohol. Attacks in women may occur after ovulation and during the last part of the menstrual cycle when progesterone levels are high. Reduced food intake, often in an effort to lose weight, as well as infections, surgery, and stressful situations may also precipitate attacks. Risk for developing chronic renal disease and liver cancer (hepatocellular carcinoma) is increased. The skin is not affected, except in some patients who have developed kidney failure.
How is Hereditary Coproporphyria diagnosed?
The diagnosis can be made by finding a definite increase in PBG and ALA as well as significantly elevated levels of coproporphyrin (especially coproporphyrin III) in urine and stool. A marked elevation in coproporphyrin III in stool is a more specific finding, but the diagnosis should be confirmed by finding the disease-causing mutation.
- Also see FAQ: What diagnostic tests are available?
What are treatments for Hereditary Coproporphyria?
Treatment, complications, and preventive measures are the same as in AIP.
The prognosis is usually good if the disease is recognized and if treatment is prompt, before severe nerve damage develops. Although symptoms usually resolve after an attack, repair of nerve damage and associated muscle weakness may require several months or longer. Mental symptoms may occur during attacks but are not chronic. Premenstrual attacks often resolve quickly with the onset of menses.
Hospitalization is often necessary for acute attacks. Medications for pain, nausea, and vomiting and close observation are generally required. During treatment of an attack, attention should be given to sodium (salt) and water balance. Harmful drugs should be stopped. Attacks are treated with either glucose loading or hemin. These are specific treatments that lower the production of heme pathway intermediates by the liver. Glucose or other carbohydrates are given by mouth if possible, otherwise by vein. However, unless an attack is mild, it is now common practice to begin treatment with hemin, which is more effective than glucose loading. Hemin therapy can be started after a trial of glucose therapy, but the response to hemin therapy is best if started early in an attack.
Patients with severe renal disease tolerate hemodialysis or kidney transplantation. Liver transplantation has been very effective for patients who have repeated attacks and who are resistant to other treatments. However, experience with transplantation as a treatment is still limited.
What are ways attacks can be prevented?
Attacks can be prevented in many cases by avoiding harmful drugs and adverse dietary practices. Wearing a Medic Alert bracelet is advisable for patients who have had attacks, but is probably not warranted in most latent cases. Very frequent premenstrual attacks can be prevented by a gonadotropin-releasing hormone (GnRH) analogue administered with expert guidance. In selected cases, frequent noncyclic attacks can be prevented by once- or twice-weekly infusions of hemin.
Individuals who are prone to attacks should eat a normal or high carbohydrate diet and should not greatly restrict their intake of carbohydrate and calories, even for short periods of time. If weight loss is desired, it is advisable to consult a physician and a dietitian to have them prescribe an individualized diet that is approximately 10% below the normal level of calories for the patient. This should result in a gradual weight loss and usually will not cause an attack of porphyria.