Friday, July 10, 2015

What laboratory test is most appropriate for this patient?

3. Calcitonin

This patient had multiple flesh-colored papules on the eyelids, lips, and tongue. This phenotype is suggestive of multiple endocrine neoplasia (MEN) type 2B (MEN-2B), an autosomal dominant condition characterized by medullary thyroid cancer among other features. Serum calcitonin can be used to screen for medullary thyroid cancer. 

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 the multiple endocrine neoplasia type 2B syndrome, an autosomal dominant condition characterized by medullary thyroid cancer, pheochromocytoma, mucosal neuromas, intestinal ganglioneuromas, and marfanoid body habitus. Although comprehensive genotyping of the RET proto-oncogene was not available at the time of this family's presentation, such analysis now allows for highly specific screening of family members and subsequent initiation of genetic counseling, pheochromocytoma screening, and prophylactic thyroidectomy. The boy continues to receive levothyroxine replacement therapy and appropriate screening investigations.


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