Abstract
<jats:p>Introduction. Multiple endocrine neoplasia type 2a is a hereditary syndrome associated with a mutation in the RET proto-oncogene, characterized by highly aggressive endocrine tumors, a high risk of recurrence, and sudden life-threatening conditions. Main components of the syndrome are medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. Aim. To describe the clinical, diagnostic, and therapeutic features of a familial case-based multiple endocrine neoplasia type 2a syndrome and to analyze the manifestation patterns of the syndrome according to the RET gene mutation type. Materials and Methods. We present two clinical cases of late sequential diagnosis of the multiple endocrine neoplasia type 2a syndrome with different clinical manifestations in two sisters aged 39 and 42 years. In the younger sister, medullary thyroid carcinoma was detected incidentally during an examination for arterial hypertension. In the second patient, a thyroid tumor was identified during a diagnostic workup following genetic testing of the younger sister, which revealed a RET gene mutation, Cys634Ser, in exon 11. This mutation is associated with a high risk of aggressive disease progression and early manifestation of medullary thyroid carcinoma. Results and Discussion. Both patients underwent total thyroidectomy with central lymph node dissection for medullary thyroid carcinoma. Dynamic monitoring of calcitonin and carcinoembryonic antigen levels in the blood, combined with imaging methods, demonstrates good efficacy of surgical treatment. During preoperative evaluation, the younger sister was found to have a right adrenal mass and the elevated blood metanephrine levels. First-degree relative screening revealed the elevated calcitonin levels and the sonographic signs of thyroid nodules in the 12-year-old daughter of the older sister. This clinical case illustrates the variable expressivity of the multiple endocrine neoplasia type 2a syndrome, which does not exclude the possibility of combined mutations in the RET proto-oncogene. Conclusions. Multiple endocrine neoplasia type 2a syndrome requires a multidisciplinary approach to both diagnosis and treatment. Patients with multiple endocrine neoplasia type 2a must be screened for the syndrome components on a lifelong basis. First-degree relatives of such patients should undergo genetic testing regardless of the initial case findings.</jats:p>