To the Editor.— Hereditary coproporphyria is a rare form of porphyria caused by an inherited partial deficiency of enzyme coproporphyrinogen oxidase. Patterns of porphyrin excretion in feces and urine are characteristic. Only 10% to 20% of enzymatic deficiency carriers present clinical manifestations. These manifestations consist of acute attacks similar to those in acute intermittent porphyria, generally less severe, and/or cutaneous photosensitivity and skin fragility similar to porphyria cutanea tarda. 1 Recently, seven cases of human immunodeficiency virus infection, five of them with acquired immunodeficiency syndrome, associated with porphyria cutanea tarda have been described. 2-5 Simultaneous occurrence of these two diseases may be coincidental; however, some pathogenic implications have been presumed. 2 We have seen a patient affected by hereditary coproporphyria who developed acquired immunodeficiency syndrome-related Kaposi sarcoma. Treatment with zidovudine was shown to be safe in this form of acute porphyria. Report of a Case.— A 35-year-old homosexual man was