Endocrine Abstracts

JOINT355

We present an 8-year-old black African girl with no significant past medical history. The patient presented with a 7-month history of profuse watery diarrhoea after moving to the UK from Nigeria. There was no history of bloody stools, abdominal pain or vomiting. The diarrhoea had worsened to approximately 10 watery episodes per day. She was noted to have progressive neck swellings with 4kg weight loss over this time, prompting emergency department attendance. There was no history of night sweats or fever. Her weight at initial assessment was 19kg. Extensive infection screen was unremarkable, including negative stool, HIV1/2 antibody, TB gamma interferon, gastric lavage and Mantoux testing. Biochemistry results were largely unremarkable, but with a noted raised calcitonin of 117,896 ng/l (reference range: 0-6.4ng/l). Plasma and urinary metanephrine levels were normal, as were parathyroid and thyroid hormone levels. The patient had ultrasound and CT imaging of her neck, chest, abdomen and pelvis. Ultrasound imaging of the thyroid gland demonstrated suspicious inhomogeneous calcified nodules. Multiple enlarged lymph nodes were visualised in the anterior and posterior triangle of right neck and left anterior neck, containing internal calcification (the largest measuring 30x27mm). Chest imaging revealed enlarged lymph nodes and scattered lung nodules. Sclerotic lesions were identified in the sacrum, iliac bone and vertebral bodies. Infiltrative pathology was also demonstrated in the pericardial area. The imaging was suggestive of an extensive malignant process, likely arising from the thyroid. Differentials included tuberculosis, carcinomatosis and sarcoidosis. The patient underwent biopsy, revealing a diagnosis of metastatic medullary thyroid cancer (MTC), with disease in thyroid, lymph nodes, lungs and bones. MTC accounts for approximately 5% of paediatric thyroid malignancies, with an incidence of 0.27/1,000,000 cases/year. MTC originates from parafollicular C-cells; these neuroendocrine cells produce calcitonin and are not responsive to thyroid stimulating hormone. Tumour secretion of calcitonin and calcitonin-gene related peptide are known causes of diarrhoea. While 80% of MTC cases are sporadic, familial forms exist within multiple endocrine neoplasia II (MENII) syndrome. Genetic screening of this patient was consistent with MEN 2b. The MEN2 form of MTC is caused by mutations in the RET proto-oncogene. Therefore, in children with MEN2 and advanced MTC, the RET tyrosine kinase pathway is a target for treatment. The patient underwent thyroidectomy with bilateral neck dissection with a plan to start RET inhibitor therapy in the following weeks. This case highlights the importance of considering thyroid pathology in children presenting with chronic diarrhoea.