Papules on the Eyelids, Lips, and Tongue

A 16-year-old boy presented with multiple flesh-colored papules and dermal nodules on his eyelids, lips, and tongue (Panels A, B, and C, respectively). Six years earlier, his mother had received a diagnosis of metastatic medullary thyroid cancer, at the age of 38 years. At that time, both of her sons were found to have markedly elevated serum calcitonin levels but no biochemical evidence of pheochromocytoma. Both boys subsequently underwent total thyroidectomy. On pathological examination, a medullary thyroid tumor measuring 0.5 cm by 0.5 cm had been discovered in the thyroid gland of this patient. This clinical history is suggestive of . . .