Over 95% of MEN2B casesresult from a pathogenic variant in codon 918 at exon 16 of the RET proto-oncogene.9 In contrast to MEN2A, MEN2B cases are more often the result of denovo germline pathogenic variants, which often leads to delayeddiagnosis.14,15 This syndrome is characterized by the development of MTC in allpatients, pheochromocytomas in up to 50% of patients, and a characteristic clinicalphenotype of a marfanoid body habitus and neuromas.11 This evidence concerns the gene RET and medullary thyroid gland carcinoma.