Hirschsprung's disease associated with isolated familial medullary carcinoma of the thyroid

We present two siblings with neonatal Hirschsprung's disease in whom isolated familial medullary carcinoma of the thyroid was diagnosed at the age of 16 and 19 years. Rectal biopsy in each patient revealed total absence of ganglion cells in the myenteric plexus and hypertrophied nerve fibers characteristic of Hirschsprung's disease. Both underwent total thyroidectomy and histological examination revealed bilateral and multifocal medullary carcinoma of the thyroid. These two patients belong to a large family in whom another 12 affected members with medullary carcinoma of the thyroid were found. Our description is the first report of an association between Hirschsprung's disease and isolated familial medullary carcinoma of the thyroid. We suggest that familial occurrence of Hirschsprung's disease could be an early presentation of familial medullary carcinoma of the thyroid either as the isolated form or as part of multiple endocrine neoplasia type IIa or IIb.