Isolated lower extremity I-131 bone marrow uptake in a runner.

A 34-year-old woman with a history of thyroidectomy for poorly differentiated papillary thyroid carcinoma but negative cervical lymph nodes underwent empiric radio-iodine therapy with 197.5 mCi Na 1-131. Her pretherapy thyroglobulin level was 2.4 ng/ml. Seven-day delayed whole-body images showed asymmetric bilateral femoral and tibial osseous uptake. The patient denied bone pain, and skeletal palpation produced no pain. She was very athletic and involved in power walking and other sports. A bone scan did not reveal skeletal metastases.