Skin eruptions following treatment with Iodine-131 for hyperthyroidism: a rare and un-reported early/intermediate side effect.

Background: Iodine-131 ((131)I) is a well-established method for the treatment of hyperthyroidism. Following such therapy, patients may experience symptoms relating to early or delayed side effects that can be prevented or minimized if necessary measures are taken. We have noticed an unusual side effect of (131)I therapy in the form of a skin eruption (iododerma) and aimed at assessing the frequency and severity of this side effect.
Material and Methods: Retrospective review of 141 patients treated with (131)I between January 1994 to December 2000 (86 F, 55 M; mean age 41.35 +/- 11.02 years) was performed. The dose of (131)I ranged from 250-500 MBq. Post therapy clinical and biochemical evaluation of thyroid function was done at 6 weeks, 3, 6, and 9 months then annually.
Results: Of the 141 treated patients, 3 patients (2.1%) presented with iododerma 4-6 weeks after (131)I therapy administration. Lesions were observed at both ankles & lower legs in all 3 cases. All lesions disappeared within 6 months with no residual effect. No other skin lesions were seen thereafter during the follow-up period.
Conclusion: Iododerma is a rare complication of (131)I therapy that has not been reported before. It appears within 4-6 weeks after therapy and is a self-limiting condition.