Abstract
Multiple endocrine neoplasia (MEN) type 1 (MEN1) and 2 (MEN2) rarely co-exist in one case. Here we report a patient with features of both syndromes. The patient presented with typical MEN1 features plus pheochromocytoma and thickened corneal nerves. She had a germline 1132delG frameshift mutation in MEN1, no mutation in CDKN1B (p27) and no RET mutation, but had both RET polymorphisms Gly691Ser and Arg982Cys. This is the first case report of a combination of typical clinical findings of MEN1 harboring a germline MEN1 mutation and the MEN2-like phenotype with negative full RET gene analysis of pathogenic variants. Possible explanations include a previously unrecognized phenotype-genotype association or the influence of potential phenotypic modifying RET variants. Furthermore, the combination observed in this patient may point to a single molecular pathway, and supports the possibility of as yet unrecognized connections between the molecular pathways for MEN1/menin protein and MEN2/RET protein.