Autonomous adenomas caused by somatic mutations of the thyroid-stimulating hormone receptor in children.

In adults, autonomous adenomas of the thyroid causing hyperthyroidism are relatively common and are most often due to somatic mutations that increase the constitutive activity of the thyroid-stimulating hormone receptor (TSHR). By contrast, autonomous adenomas in hyperthyroid children are exceptional and reports of their clinical and molecular characteristics are few. We reviewed papers describing 16 autonomous adenomas due to a somatic mutation activating the TSHR and diagnosed in patients younger than 18 years, to which we added two of our own unpublished observations in a 4- and 8-year-old with the same TSHR mutation (c.CAG>CAC; p.Asp633His). This revealed that (a) autonomous adenomas occur more often in the right lobe (11 of 14 with available information) and the associated hyperthyroidism tends to be more severe, possibly reflecting the richer vascular supply of the right thyroid lobe, and (b) mutations found in benign adenomas in children have been associated with cancer in adults, suggesting that malignancy requires a second 'hit' at a later age.