Porphyrin enzyme analysis in an oral pathology practice: a look back over four years

Porphyric neuropathy

The hepatic porphyrias are a group of rare metabolic disorders characterized by enzymatic defects in the biosynthesis of heme, a metalloporphyrin that is the principal product of porphyrin metabolism. The hepatic porphyrias are genetically transmitted as autosomal-dominant disorders with variable expression that produce a particularly severe form of neuropathy. Most medical students readily recognize acute attacks of porphyria when the classic triad of abdominal pain, psychosis, and neuropathy is present. Yet, porphyric neuropathy is a source of confusion in practice, and patients with porphyria rarely receive the correct diagnosis early in the course of the illness. Porphyric neuropathy is manifest by symptoms, signs, and cerebrospinal fluid abnormalities resembling acute Guillain-Barré syndrome. However, accompanying psychological features, a proximal predilection of asymmetric weakness, and electrodiagnostic findings indicative of an axonal polyradiculopathy or neuronopathy all suggest the diagnosis of porphyria. Confirmation of the diagnosis depends on use of appropriate laboratory studies. The underlying pathophysiology of porphyric neuropathy has not been established, but it may be related to direct neurotoxicity of elevated levels of delta-aminolevulinic acid. The severity of the neuropathy and the availability of potential treatments, including avoidance of provocative factors, make identification important.

The porphyrin pathway: the final common pathway?

When I was learning pathology a wise and knowledgeable mentor described a final common pathway that allows many diseases to overlap in their presentation. This pathway was never identified for it was unknown. Recent books by physicians have suggested that maintaining body balance and/or treatment by a substance could halt or repair damage caused by a wide array of diseases, once again suggesting a common thread amongst diseases. Again no mention was made regarding what was this common denominator. I have been interested in people who have more than one disease, feeling that there must be a link. My interest in the porphyrin pathway has strengthened that impression. Since finding Doss's list of diseases having porphyrin abnormalities unrelated to a porphyria, I have worked on models that would allow me to show a way where porphyrin abnormalities may be a part of the final common pathway for all disease. I have finally decided that a spider's web is that model. The following discussion will attempt to demonstrate that this hypothesis could be true.

Porphyria and chemicals

Porphyria is a genetic family of diseases that is most frequently described as neuropsychiatric or toxogenetic. It is well known to be initiated by drugs, infections, heavy metals, hormones, chemicals and fasting. There are extensive lists of drugs that have been known to cause attacks. Others are thought to be likely to cause attacks on the basis of animal studies or in vitro studies. It has become obvious that lists of chemicals capable of causing illness in porphyrics are sorely lacking. Chemicals that have the same base as drugs that are labeled in the PDR (Physicians Desk Reference) as porphyrogenic have no such labeling in their MSDS (Material Safety Data Sheet). This article is intended to point out why porphyria needs to be considered when illness occurs after chemical exposure. The capability of testing enzymes in the porphyrin pathway allows us to evaluate these patients more thoroughly, for we are now aware that the standard measures for recognizing these diseases are often inadequate. Three examples where illness has occurred after environmental exposure to chemicals will serve as illustrations. One, a documented porphyria, is the Turkish porphyria. The other two are not yet documented as porphyria, but may be some day. One is Agent Orange which caused illness in Vietnam, and the other is exposure to unknown sources of what has been named the Gulf War syndrome.