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With reference to an observation of porphyria variegata, which was complex and unusual as all such observations are, the direct responsibility of rifampicin is underscored. Porphyria variegata should be considered in two situations. The first of these is a dramatic acute neuroabdominal picture: the diagnosis of acute hepatic porphyria is established by the measurement of urinary porphyrins; the second step is to distinguish between the three acute hepatic porphyrias by looking for cutaneous manifestations and determining the respective proportions of coproporphyrins and protoporphyrins in the stools. In porphyria variegata, fecal protoporphyrins are significantly increased. The second situation is cutaneous involvement suggestive of late-onset cutaneous porphyria: porphyria variegata as well as hereditary coproporphyria in the cutaneous phase must be considered. Diagnosis can be established only through measuring fecal porphyrins. Porphyria variegata is a genetic enzymatic disorder inherited on an autosomal dominant basis. A study of the family is required in all cases, but the conventional methods for detecting heterozygotes for porphyria variegata are not satisfactory. Carriers will be unequivocally distinguished from healthy subjects only through measuring the defective enzyme activity.