Suggested pathobiochemical development of chronic hepatic porphyrias

Multiple nodular foci in the liver associated with chronic hepatic porphyria after previous treatment of breast cancer

More than 7 years after the diagnosis and treatment of breast cancer (T1N1aM0), multiple nodular foci were observed in the liver of a 40-year-old woman at ultrasonographic examination. The lesions were confirmed by CT scan, but CT-guided liver biopsy revealed only non-specific alterations. At subsequent peritoneoscopic examination, bluish-brown foci were indeed visible on the liver surface, but guided liver biopsies again failed to corroborate the suspected metastases. Instead, histology showed mild portal fibrosis, moderate steatosis and siderosis of hepatocytes, as before. Only the intense red fluorescence of part of the biopsy material under Wood's light suggested the diagnosis of chronic hepatic porphyria or porphyria cutanea tarda, here presumably as a consequence of prolonged alcohol consumption. Subsequent porphyrin studies in urine, faeces and plasma yielded the typical constellation of latent porphyria cutanea tarda (chronic hepatic porphyria type C). The activity of erythrocyte uroporphyrinogen decarboxylase was normal, which argued against a genetic predisposition. After 1 year of strict alcohol abstinence and low-dose chloroquine treatment the "nodular foci" in the liver were no longer visible on ultrasonogram and CT scan; only proton-weighted NMR imaging (SE 1500/30) still showed ill-defined areas of higher signal intensity. The renal excretion of porphyrins had decreased considerably. The levels are now consistent with the diagnosis of subclinical chronic hepatic porphyria type A. Modern non-invasive imaging techniques are tremendously useful, but they have their pitfalls. Focal liver lesions may present serious diagnostic problems, especially when they are found in a patient with a history of carcinoma at an extrahepatic primary site. A rare example is described.(ABSTRACT TRUNCATED AT 250 WORDS)

Porphyria cutanea tarda, or the uroporphyrinogen decarboxylase deficiency diseases

The term "porphyria cutanea tarda" originally described the dermatological manifestations of various chronic porphyrias. Its usage now is usually restricted to disorders associated with a deficiency of uroporphyrinogen decarboxylase (UROD), for which the term "UROD-deficiency" may be more appropriate. Four etiologic agents have been implicated in this condition: alcohol, oral estrogens, halogenated aromatic hydrocarbons, and iron. An inherited deficiency of UROD is also recognized, with increased susceptibility to these agents. Certain halogenated aromatic hydrocarbons can cause UROD-deficiency in animals and synergism with iron is demonstrable in this model. Neither ethanol nor estrogen has been shown to cause UROD-deficiency in animals. Treatment by venesection to reduce total body iron is safe and effective. The 4-aminoquinoline antimalarial drugs also provide effective treatment, possibly by lysis of affected liver cells. Unlike venesection, they may not reverse the biochemical lesion which causes porphyrins to accumulate. The mechanism of acquired UROD-deficiency is not clear but animal studies suggest a role for the hepatic mixed function oxygenases which initiate iron-dependent inactivation of UROD. Diagnosis is simple, often requiring only appropriate clinical data and testing of a random urine sample. Although not common, the disorder is the most frequently diagnosed disturbance of porphyrin metabolism in many countries, and further insight into its unusual pathogenesis may clarify the hepatotoxic effects of the 4 etiologic agents.

Decreased hepatic uroporphyrinogen decarboxylase activity in porphyria cutanea tarda

To test whether reduced hepatic uroporphyrinogen decarboxylase activity is a specific and intrinsic defect in porphyria cutanea tarda, we measured enzymatic activity in the livers of 17 patients with porphyria cutanea tarda, 12 "normal" control patients without liver disease, and 41 patients with other forms of porphyria, alcoholic liver disease, hemochromatosis, or chronic hepatitis. Enzyme activity in all the patients with porphyria cutanea tarda was lower than in the patients without this disease, except for one patient with alcohol-induced fatty liver. Reduction of hepatic iron stores by phlebotomy did not alter the enzymatic activity in porphyria cutanea tarda. We conclude that reduced hepatic uroporphyrinogen decarboxylase activity is a specific and intrinsic hepatic defect in porphyria cutanea tarda, but modulation of uroporphyrinogen synthesis by extrinsic factors is required for the full biochemical expression of the disease.