Based on the clinical manifestations of MTC, mucosal neuromas on the tongue, ganglioneuromatosis of the gastrointestinal tract, Marfan-like appearance, and a peculiar face, we clinically diagnosed the patient with MEN 2B and confirmed a germline pathological variant of RET gene, p.Met918Thr (c.2753T > C). This evidence concerns the gene RET and multiple endocrine neoplasia type 2B.