[Naproxen-induced pseudoporphyria].

A 12 year old boy developed scars at light-exposed areas following long-term therapy with naproxen for rheumatoid arthritis. Erythrocyte and urine porphyrin levels were not increased, and there was no evidence of increased photosensitivity. Pseudoporphyria is reported in 10-20% of those treated with naproxen for > 4 weeks. As compared to other nonsteroidal anti-inflammatory agents, the specific risk for naproxen is increased about 6fold. While the underlying abnormality has not been elucidated, formation of phototoxic metabolites in a subgroup of genetically predisposed individuals has been suggested as the most likely mechanism. Both dermatologists and rheumatologists should be aware of the risk of naproxen-induced pseudoporphyria and discontinue therapy early in order to avoid scar formation in light-exposed areas.