--Disease Characteristics-- Documented acute intermittent porphyria, variegate porphyria, or hereditary coproporphyria causing 6 or more attacks per year Fewer than 2 attacks in the preceding 6 months if already on preventive heme therapy --Prior/Concurrent Therapy-- See Disease Characteristics --Patient Characteristics-- Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Urinary porphobilinogen at least 20 mg/24 hours during acute symptoms Other: Not pregnant Fertile female patients must use effective contraception during and for 6 months prior to study No recurrent symptoms due to another illness No continuous (for longer than 1 month) symptoms of porphyria unless it is in addition to acute exacerbations No acute hemorrhagic disorder such as: Gastrointestinal bleeding Intracerebral hemorrhage No known hypersensitivity to tin mesoporphyrin No known hypersensitivity to any intravenous heme preparation No other condition which may increase risk to patient