[Clinical manifestations, therapeutic response to tyrosinase inhibitor and RET gene activating mutation in a patient with multiple endocrine neoplasia 2B].

OBJECTIVE: To explore the clinical manifestations, therapeutic response and RET gene mutation in a patient with multiple endocrine neoplasia 2B (MEN2B) characterized by medullary thyroid carcinoma (MTC), bilateral adrenal pheochromocytoma and multiple mucosal neuromas.

METHODS: The clinical features, laboratory data and radiological manifestations of this patient were collected. Genomic DNA was extracted from her peripheral blood leukocytes and her parents. Tenth to sixteenth exons of RET proto-oncogene, including the flanking regions of introns, were amplified by polymerase chain reaction (PCR). And the mutations of RET proto-oncogene were identified by direct sequencing.

RESULTS: MEN-2B was diagnosed by the clinical presentations, laboratory tests and radiological findings. Gene analysis confirmed heterozygous mis-sense mutation at codon 918 in exon 16 of RET proto-oncogene in which thymine was replaced by cytosine (ATG→ACG). Her thyroid medullary carcinoma was treated by radical operations and radiotherapy. Tyrosinase inhibitor sorafenib was administered for 2 months and watery diarrhea and cough were alleviated. The drug was withdrawn because of such intolerant side effects as hair loss and painful rashes. She had a survival time of over 14 years with multiple system tumor metastases.

CONCLUSIONS: The mutation analysis of RET proto-oncogene confirmed the diagnosis of MEN2B in respect of molecular genetics. For patients with advanced MTC, tyrosinase inhibitors may relieve the symptoms and provide a new therapeutic choice.