Inheritance: autosomal dominant, but new mutations may occur
Gene affected: RET proto-oncogene (causes germline activation)
Features seen in 95-100% of patients:
(1) medullary carcinoma of the thyroid (100%)
(2) marfanoid habitus
(3) mucosal neuromas (tongue, lips, subconjunctiva)
(4) intestinal ganglioneuromatosis
Features seen in 50% of patients:
(1) unilateral or bilateral pheochromocytomas
Other findings:
(1) intestinal colic with diarrhea during infancy
(2) pectus excavatum
(3) slipped femoral epiphysis
Parathyroid adenomas or carcinomas are rare.
Causes of death:
(1) metastatic medullary carcinoma, which may occur in infancy
(2) hypertensive crisis due to the pheochromocytoma
Laboratory tests may include:
(1) serum calcitonin, for medullary carcinoma
(2) plasma metanephrines, for pheochromocytoma
(3) 24 hour urine for catecholamines or metanephrines, for pheochromocytoma
Once a family has been identified, family members are tested for RET mutations.
