Chemical Injury and Disorders of Porphyrin Metabolism
Some chemically-injured patients with Multiple Chemical Sensitivity (MCS) show disturbances in their body's system for making heme, which is the primary component of hemoglobin in red blood cells. Their lab tests reveal abnormal activity in one or more of the eight enzymes involved in heme production. Since most heme is made in the bone marrow, these "disorders of porphyrin metabolism" are usually found there or in the liver. They can have a disruptive effect on numerous processes that rely on heme and hemoglobin. Of clear concern to MCS patients are the "cytochrome P450" enzyme system, which uses heme to detoxify chemicals in the liver and other vital organs, and the oxygen transport system, which relies on hemoglobin to carry oxygen from the lungs to other body organs.
The term porphyria (pour-'fury-a) refers specifically to a group of diseases in which cells in the liver and/or bone marrow (primarily) are unable to properly carry out all the steps involved in making heme, due to an inherited defect (or "inborn error") in one or more of the eight enzymes involved. The symptoms that result may involve any part of the nervous system (central, peripheral and autonomic) or just the skin or both. Symptoms are triggered by exposure to sunlight (in photosensitive cases) and/or by exposure to "porphyrogenic" drugs or chemicals, infections and other stressors. When the heme-making pathway is disrupted in this way, the excess porphyrins which are no longer metabolized start to accumulate in certain body organs where they can have toxic effects.
The most common type is Porphyria Cutanea Tarda, or PCT, which is one of four non-acute porphyrias. Patients with PCT and the other non-acute porphyrias have a variety of skin symptoms as a result of often severe "photosensitivity" to sunlight. PCT also may be acquired in response to toxic drug or chemical exposure and is made worse by such exposures. (In 1993, the Department of Veterans Affairs accepted an Institute of Medicine recommendation to pay compensation to Vietnam Veterans with PCT, on the assumption that their PCT was most likely caused or aggravated by exposure to the dioxin in Agent Orange.)
There also are four "acute" types of inherited porphyria which may display an even wider variety of symptoms. They all feature neurological problems and many also have psychological and/or skin symptoms. In three of these types, an estimated 90% of those with the inherited enzyme deficiency have no symptoms until their disease is triggered, often in mid-life, by some toxic drug, chemical or metal exposure or by some internal stress such as liver disease, hormonal changes, or dieting. In acute types (and in PCT), once symptoms begin they usually continue in response to many kinds of exposures and often include chronic as well as acute aspects.
The term porphyrinuria (pour-'frin-ur-E-a) is used to categorize disorders of porphyrin metabolism and excretion that are acquired from diseases, drugs or chemicals with or without inherited enzyme abnormalities. These porphyrin disorders usually are found in the liver and are called coprophyrinuria when limited to coproporphyrins. Physical symptoms may be chronic, evident only during periods of acute attack, both chronic and acute, or they may be absent altogether. Drugs and chemicals can cause porphyrinurias by triggering the cytochrome P450 system which in turn can overload the heme pathway. A secondary porphyrinuria or coprophyrinuria is a porphyrin abnormality that occurs secondarily to some other disease which usually test positive for some but not all of the diagnostic markers associated with true porphyrias.
The broader term "porphyrinopathy" is used here to refer to any disorder of porphyrin metabolism, inherited or acquired. The porphyrinopathies being seen in chemically-sensitive patients do not fit the patterns of any known type of inherited porphyria. This suggests that they may be the result of an acquired abnormality, due either to the direct effects of a chemically-induced porphyrinopathy or the secondary effects of some other disease.
The "acute" porphyrias always display neurological symptoms affecting the central, peripheral and/or autonomic nervous systems. These may include any combination of abdominal pain, nausea, vomiting, constipation, seizures, headaches, difficulty concentrating, personality changes, weakness and aching in muscles and joints, unsteady gait, poor coordination, numbness/ tingling of arms and legs, retaining fluids, rapid heart rate, increased blood pressure, increased sweating, and intermittent fever.
Acute and chemically-acquired cases also show increased sensitivity to a long list of exposures that may both bring on symptoms and make them worse. These include certain medications (the focus of much porphyria research), toxic chemicals (such as PCBs and dioxin), alcoholic beverages (including beer and wine), other liver diseases (like Hepatitis C and cancer) as well as more subtle factors like hormonal changes and a low carbohydrate diet. (Skipping meals and dieting make symptoms worse, while chemicals that mimic the female hormone estrogen are known to trigger acute porphyrias--both of which may contribute to the higher incidence of acute porphyrias in females.) There is also one report documenting acute skin sensitivity to copper in dental patients with coproporphyria. (Copper is found in significant amounts in the silver and gold used for both dentistry and jewelry, and skin sensitivity can be tested easily by wearing a copper bracelet; if sensitive, symptoms should appear in a few minutes to a few hours.)
When the skin is involved, as it is in all non-acute and some acute types, symptoms from sensitivity to sunlight may include a wide variety of problems such as rashes, blisters, changes in skin pigment, changes in facial hair, and fragile skin that injures more easily. Porphyrinopathy patients also may occasionally notice discolored urine, either dark brown or pink to red ("port-wine" colored) and not due to blood. It is from this sometimes dark purplish color--"porphyra" in Greek--that porphyria takes its name. (In the "Madness of King George," a 1995 film about the acute porphyria that afflicted King George III, the urine is portrayed as blue.) Any change in urine color is most likely to occur during an illness reaction, and the dark color may be more obvious after the urine has been left standing for a few hours exposed to light or heat. (None of the underlined symptoms above would be expected in cases of MCS unless due to a disorder of porphyrin metabolism.
Some persons with "acute" types of porphyria excrete porphyrin substances in the urine and/or stool only in response to exposures that make them ill. Their tests are more likely to show changes in the first 2 to 3 days after the onset of a reaction. Thus, urine and stool testing is most sensitive and accurate during that time. Dr. Ziem recommends you not induce a reaction, but have the lab form, and when a reaction occurs, go for the testing. The form explains how to collect the specimens.
How are Disorders of Porphyrin Metabolism diagnosed?
Each type of porphyria is defined by specific symptoms and diagnostic signs or "markers," although these overlap considerably in some types. If a disorder of porphyrin metabolism is suspected on the basis of symptoms, diagnostic tests are usually ordered of urine and stool and sometimes also of blood and plasma to look for characteristic abnormalities of enzyme(s), porphyrin(s) and/or porphyrin "precursors" (substances called ALA and PBG which are measured to check the activity of the first two enzymes in the heme pathway). If acute porphyria is suspected, this testing must be done when patients symptoms are worse than usual. Chemically-acquired porphyrinopathies are more variable and often mimic one or more elements of the different inherited types, but they can be tested and treated in the same way. Since ALA and PBG are always elevated in urine during acute attacks, these porphyrin precursors are sometimes used alone for screening potential cases. They may normal, however, in latent cases as well as those in remission, in between attacks, and/or those with more chronic symptoms. They also cannot distinguish between different types of porphyrinopathy.
To be definitively diagnosed, an active case of inherited porphyria or acquired porphyrinopathy should show evidence of all the following:
1. Abnormal enzyme activity in one or more of the eight porphyrin enzymes. (Even if the patient has never had symptoms, this alone is enough to diagnosis a latent case of porphyria.)
2. Abnormal levels of porphyrins and/or porphyrin precursors in the urine, stool, blood and/or plasma (although they may be so only during acute attacks).
3. Acute and/or chronic symptoms typical of porphyrinopathies that are not explainable by other diseases or other forms of chemical injury.
MCS Referral & Resources offers a detailed testing protocol developed by Dr. Grace Ziem and Albert Donnay to assist doctors in evaluating disorders of porphyrin metabolism in chemically-injured patients. It contains this fact sheet as well as a laboratory request form, instructions for patients, diagnostic information for physicians, interpretive tables, and a long list of drugs and chemicals known to trigger symptoms of acute porphyrin disorders. We encourage patients to discuss this protocol with their physician(s) to see if it is appropriate for them. Any lab can collect the required blood, urine and stool specimens, but the protocol requires that these be sent for analysis to the Mayo Medical Laboratory, which is a world-renowned center for porphyria research.
The blood relatives of patients with an inherited porphyria may have the same enzyme defect but no symptoms. About 90% of these "latent" or silent cases never develop symptoms, but the other 10% are usually ill by mid-life. Since it is not known which particular exposure(s) may eventually provoke their disease, latent cases should be informed about the potential risk posed by exposures to "porphyrogenic" substances (like alcohol, and specific drugs and chemicals) that may trigger their disease. This applies both at home and in the workplace. MCS patients who test positive for abnormalities that are characteristic of one of the inherited porphyrias may want to encourage their immediate family members to be tested as well, starting with their biological parents, if possible. If both parents are normal, the porphyrin disorder is not inherited and other blood relatives (children, brothers and sisters) need not be tested.
Both conditions report increased sensitivity to certain chemicals, drugs and alcohol. Many other symptoms are similar. Two separate medical practices in Washington State have tested over 150 of their MCS patients with symptoms of porphyrinopathy. According to analyses done by Mayo's Porphyria Lab, over 70% of them had excess porphyrins and/or enzyme abnormalities in patterns that did not match those of any inherited porphyrias. Disorders of porphyrin metabolism may account for many of the symptoms seen in MCS cases (and possibly also cases of CFS/CFIDS, fibromyalgia, Persian Gulf Syndrome and silicone breast implant disease), but they do not explain all the symptoms and may not be present in all cases, which suggests that other mechanisms of chemical injury must be involved. Some MCS patients, for example, show evidence of direct neurotoxicity in the brain, as well as impaired functioning of the limbic, respiratory and immune systems, none of which are usually associated with porphyria or porphyrinuria (although these have not been ruled out).
In some acute porphyrias and porphyrinurias, excess porphyrins and/or porphyrin precursors may be evident only during an acute reaction. Testing should be repeated when you feel your symptoms are significantly increased and should check for an excess of porphyrins in all possible locations: urine, stool, plasma and whole blood. If repeated testing even when your MCS symptoms are worse than usual finds no abnormal levels of enzymes, porphyrins or their precursors, then you do not have a disorder of porphyrin metabolism (at least not one detectable by Mayo's current laboratory methods). These MCS cases may be called "non-porphyric MCS" to distinguish them from those in which porphyrin disorders are involved.
When secondary porphyrinurias are suspected, treatment should focus on the primary disease causing the porphyrinuria. In the case of inherited porphyrias and toxic acquired porphyrinurias, there is no known cure, but proper precautions may greatly reduce symptoms and long-term damage to the body. As with MCS, the recommended "treatment" for acute porphyrinopathies focuses on the need for patients to avoid all exposures that may provoke their symptoms. Patients are advised strongly to:
Hundreds of drugs and chemicals that are known or suspected of triggering symptoms in cases of acute and acquired porphyria have been identified, and these should be avoided unless medically essential. (A partial list is available from MCS Referral & Resources.) Unfortunately, many thousands more have never been tested. People with porphyria are likely to react badly to some medications, have chemical injury in other body organ systems and beware could react to medications that are not believed to aggravate porphyria. Medications (and chemicals) to avoid include those broken down by means of "oxidation" or "hydroxylation," steroids, those which mimic the female hormone estrogen, and those which induce the cytochrome P450 system in which heme plays such an important role.
Although some lists of "safer" medications have been published by porphyria researchers, new medications should be tried only one at a time and under close medical supervision. They may not be safe in combination and reactions among porphyria patients are known to vary significantly.
patients with porphyrinopathies should wear a Medic Alert bracelet, as
noted above, and be sure to provide both Medic Alert and their local doctor
with a list of the "porphyrogenic" medications to be avoided. If your
doctor prescribes any new medication, ask if it is broken down in the
body by oxidation or hydroxylation processes. If so, an alternative medication
should be considered.
It should. Disorders of porphyrin metabolism, although rare, are widely accepted by the medical community, and "porphyrinurias" have been listed by the International Classification of Diseases since 1920 (currently ICD 277.1). The diagnostic need for detailed biochemical testing is well established in the medical literature (urine and/or stool testing alone are insufficient). There also is broad agreement that the primary focus of treatment in acute cases must be on the avoidance of exposures that may trigger an attack, just as recommended for MCS. Since so many types of porphyria have such potentially serious consequences, there is no excuse for denying complete and prompt evaluation in any suspected case.
Please let your
physician and MCS Referral & Resources know if your insurance company
refuses to pay for porphyria diagnosis and/or treatment. You may want
to appeal, and we may be able to help.
A packet of medical papers on porphyria and a brief bibliography are available from the National Digestive Diseases Information Clearinghouse, 301-654-3810.
You also may wish to contact the American Porphyria Foundation (713-266-9617), which publishes a newsletter and brochures about different aspects of the inherited porphyrias and their treatment (via diet and hematin, for example). Except for Porphyria Cutanea Tarda, however, they offer no information on chemically-acquired disorders of porphyrin metabolism or "porphyrinuria."
Berkow R (ed.) 1992. The Merck Manual of Diagnosis and Therapy, 16th edition, Rahway, NJ: Merck Research Laboratories, pp. 1026-1038.
Bloomer JR and HL Bonkovsky. 1989. "The Porphyrias," Disease-a-Month, vol.35, no.1, pp.1-54.
Kappas A, S Sassa, RA Galbraith, and Y Norman. 1989. "The Porphyrias" in The Metabolic Basis of Inherited Disease, Scriver CR, AL Beaudet, WS Sly, and D Valle (editors), 6th edition, New York: McGraw-Hill Information Services Company, pp.1305-1365.
Moore MR, KEL McColl, C Rimington, and A Goldberg. 1987. Disorders of Porphyrin Metabolism, New York: Plenum Medical Book Company.
Scriver CR, AL Beaudet, WS Sly, and D Valle (editors). 1995. The Metabolic Basis of Inherited Disease, 7th edition. New York: McGraw-Hill Information Services Company, 2103-2159.
Silbergeld EK and BA Fowler (editors). 1987. Mechanisms of Chemical Induced Porphyrinopathies, Annals of the New York Academy of Sciences, volume 514.
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