Rifampicin-induced porphyria cutanea tarda.

A patient who developed porphyria cutanea tarda and disturbed liver function tests following treatment with rifampicin and isoniazid for a tuberculous psoas abscess is reported. The patient had normal liver function tests prior to receiving anti-tuberculosis chemotherapy, but was subsequently demonstrated to have cholelithiasis. Challenge testing with both drugs incriminated rifampicin as the agent precipitating porphyria cutanea tarda and disturbance of the liver function tests particularly the serum bilirubin. The association between rifampicin and porphyria cutanea tarda has not previously been described but might be expected because of the ability of rifampicin to induce various liver enzyme systems including delta aminolevulinic acid synthetase activity. This further illustration of rifampicin hepatotoxicity emphasizes the need for regular monitoring of liver function when rifampicin is prescribed. Rifampicin should be used with extreme caution in any patient with a previous history of porphyria cutanea tarda.