Lead Poisoning: A New Biochemical Perspective on the Differentiation Between Acquired and Hereditary Neuroporphyria

Hereditary neuroporphyrias [aminolevulinate dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria, or variegate porphyria (VP)], and lead poisoning (LP), which is thought to be an acquired form of neuroporphyria, are characterized by enzymatic inhibitions along the heme biosynthetic pathway (1)(2)(3). As a result, they share a few biochemical and clinical features. For this reason, LP may erroneously be diagnosed as hereditary porphyria, especially in cases when LP arises from unexpected sources such as consumption of Chinese herbal tea (4) and others (5)(6). Because LP is not suspected, direct determination of blood lead is not analyzed and LP is misdiagnosed. This work addresses the problem from a biochemical rather than a clinical standpoint, aiming at defining biochemical criteria that can differentiate LP from acute neuroporphyria and enable the staff in porphyria reference laboratories to diagnose LP indirectly. The study was based mainly on the biochemical findings in patient 1, whose clinical case has been reported previously in detail (7). The patient, a 43-year-old man, was referred to the hospital because of severe abdominal pain followed by constipation. He was given diclofenac, and further deterioration was noted. Because of the data described above and the fact that his urine had a color of “port wine”, an acute attack of neuroporphyria was suspected. The procedure that led to the exclusion of hereditary neuroporphyria and the establishment of a diagnosis of LP are described below. The diagnosis was confirmed by the toxicology laboratory in which a blood lead concentration of 5.3 μmol/L was measured (upper limit of normal, <0.97). The source of LP was an Indian herbal remedy the patient had taken to treat mild diabetes for 3 months before hospitalization. Each pill (8 per day) contained 10 mg of lead, leading to a monthly intake of 2.4 …