INTRODUCTION AND IMPORTANCE: Multiple endocrine neoplasia type 2A (MEN2A) is a rare hereditary cancer syndrome marked by medullary thyroid carcinoma (MTC), pheochromocytoma, and primary hyperparathyroidism. The RET proto-oncogene mutation, particularly the C634R variant, significantly increases the risk of persistent or recurrent disease. This case underscores the importance of genetic analysis and comprehensive follow-up in managing MEN2A. CASE PRESENTATION: We report a 36-year-old pregnant female with MEN2A, diagnosed with the RET C634R mutation. Ten years earlier, she underwent a total thyroidectomy for MTC, followed by an adrenalectomy for bilateral pheochromocytoma. Despite these interventions, her calcitonin levels never normalized, and recent imaging revealed somatostatin receptor-expressing lesions in the left paratracheal region. Genetic testing confirmed the RET C634R mutation, also found in her 7-year-old daughter, indicating familial transmission. CLINICAL DISCUSSION: The RET C634R mutation is associated with a high risk of MTC recurrence and poor prognosis, emphasizing the need for vigilant monitoring. This case highlights the challenges in managing MEN2A, particularly in the presence of persistent lymph node involvement. It also stresses the importance of genetic counseling for at-risk family members. CONCLUSION: This case emphasizes the critical role of genetic testing, continuous monitoring, and a multidisciplinary approach in MEN2A management. The identification of the RET C634R mutation in both the patient and her daughter highlights the need for early intervention and personalized treatment strategies to improve outcomes.