Further discussion concerning porphyria cutanea tarda and TCDD exposure.

Past reports have correlated a diagnosis of porphyria cutanea tarda (PCT) with exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Re-examination of the literature, however, has caused us to question the conclusion of a relationship between acquired PCT and TCDD. The major considerations at issue were: (1) whether the diagnostic label of PCT was applied excessively to cases with findings that are nonspecific; (2) whether the clinical conditions suggestive of PCT were the likely results of exposure to another chemical, for example hexachlorobenzene (HCB); and (3) whether a causal link between PCT and TCDD is reasonably substantiated by the facts. Based on the re-evaluation of the literature, the known effects of HCB and TCDD, and the follow-up results from the chemical plant, we submit that HCB alone, or HCB in combination with other polychlorinated aromatic hydrocarbons, may have been responsible for the effects observed and the subsequent correlation to PCT.