Human protoporphyria: reduced cutaneous photosensitivity and lower erythrocyte porphyrin levels during pregnancy.

Women with erythropoietic protoporphyria (EPP) have reported increased sunlight tolerance during pregnancy. Review of clinical information in an existing database for an EPP population study found five women who had six pregnancies while enrolled. All had experienced attenuated photosensitivity during gestation. Our purpose was to gain insight into whether altered porphyrin metabolism during pregnancy might explain this phenomenon. Erythrocyte protoporphyrin levels obtained for these women during six periods of gestation were compared with data accumulated over the course of several years during nongestational periods. Erythrocyte porphyrin levels were lower during pregnancy. The differences of the means for values obtained during nongestational periods versus values obtained during pregnancy for each woman were found to reach or approach significance (p < 0.05) by a paired t test when analyzed without regard for seasonality (p = 0.042) or when adjusted for possible seasonal effects of sunlight on erythrocyte porphyrin levels by separation into data sets for low sunlight months (October-April) (p = 0.039) or high sunlight months (May-September) (p = 0.057). These observations suggest that a beneficial physiologic effect of pregnancy in patients with EPP may be a lower circulating erythrocyte protoporphyrin burden that leads to reduced photosensitivity.