Adverse allergic reaction to 131I MIBG.

No adverse allergic reactions to iodine-131-metaiodobenzylguanidine (131I MIBG) at a diagnostic dose have been reported in the English literature. This report of a skin eruption in a 35-year-old man after an intravenous injection of 131I MIBG strongly suggests an adverse allergic reaction, and is the first to address such a side effect of 131I MIBG at a diagnostic dose. Erythematous maculopapular eruptions, some of which were contiguous, were seen in a symmetric disposition on the patient’s chest walls, elbows, neck and face 18 h after the 131I MIBG injection. Antiallergic treatment resolved the lesions completely. There were no possible causes of the exanthema other than the 131I MIBG injection. Urticaria related to the 131I MIBG injection and caused by type I allergic reaction was suspected, and these findings point to the possible risk of a hitherto unreported allergic skin reaction to 131I MIBG. We would like to draw the attention of nuclear physicians to this possible drawback of 131I MIBG.