[Porphyria and porphyrinuria]

In latent hepatic porphyria normal porphyrins are frequently excreted, but porphyrinuria accompanies many clinical conditions not associated with porphyria. Therefore, the diagnosis of latent porphyria cannot be made by examining for urinary porphyrins alone. We use 16 laboratory methods, some of which which we developed, including sensitive HPLC separation procedures, for determining relevant enzymes, and porphyrins and their precursors in urine, feces and blood. These methods enable use to distinguish between changes in porphyrin metabolism observed in many cases of latent porphyria, as opposed to similar changes which may occur during therapy with certain drugs and in common clinical conditions. During the past 4 years we investigated 406 patients suspected of porphyria. 160 had increased excretion of porphobilinogen, and/or aminolevulinic acid, and/or porphyrins. 87 of them had porphyrinuria only. Without our clinical and laboratory experience, all would have been diagnosed as porphyria. Further examinations revealed that only 14 had porphyria, 8 of whom had porphyrinuria and 6 had normal urinary porphyrins. Overall, there have been 44 families with porphyria diagnosed in our laboratory since 1969, 1 with erythropoietic protoporphyria and the others with hepatic porphyria. In the past decade, the number of patients diagnosed during the latent phase has increased markedly. This points both to increased awareness of porphyria by physicians and to the increased skills of the laboratory staff.