Patients with acute intermittent porphyria can be subdivided into three groups, according to the porphobilinogen deaminase activity in their erythrocytes. The first group has lowered, the second overlapping and the third normal porphobilinogen deaminase activity. Of 385 acute intermittent porphyria patients 5% had normal porphobilinogen deaminase activity. Gene carriers of acute intermittent porphyria, which have normal porphobilinogen deaminase activity but display slight, moderate or high aberrations of excretion, are recognized by analysis of urinary haem precursors and faecal poiphyrins. Six individuals suffering from acute intermittent porphyria were detected in three families with normal porphobilinogen deaminase. There were no differences in the latent and clinical phases of acute intermittent porphyria between patients with lowered and those with normal porphobilinogen deaminase. One female with normal activity in erythrocytes, in which the porphyria disease process is triggered by barbiturates and carbamazepin, is presented. After therapy with high doses of glucose and omission of inducing agents, this woman was free of symptoms, and the excretion of different urinary porphyrin precursors and porphyrins decreased by between 65 and 93%.

The influence of hormonal oral contraceptives on the urinary porphyrin excretion of 40 healthy females has been studied. Two different hormonal oral contraceptives (combinations of gestoden or desogestrel, respectively, and ethinylestradiol) were applied for half a year. In each case twenty women received one of these two combinations. Porphyrin precursors delta-aminolevulinic acid and porphobilinogen were normal in all subjects as well as the mean of uroporphyrin and coproporphyrin. One healthy female developed a mild secondary coproporphyrinuria. In this case coproporphyrin isomer I was slightly enhanced and isomer III slightly lowered. Furthermore it could be shown that three females with repeated premenstrual clinical expression of an acute hepatic porphyria (acute intermittent porphyria and hereditary coproporphyria) could be treated successfully with a hormonal oral contraceptive or other exogenous hormones to stabilize the latent, subclinical phase of the disease.