Endocrine Abstracts

Introduction: The commonest pathological cause of goitre in adolescence in the UK is autoimmune thyroid disease. Other thyroid pathologies may occasionally co-exist either linked to the autoimmune process or occurring together by chance.

Case report: A previously fit and healthy 15-year-old male presented as an emergency with a 10-day history of painless neck swelling. He had no breathing difficulty, dysphagia or voice change and was also clinically euthyroid. There was a family history of autoimmune thyroid disease and type 1 diabetes mellitus. On examination he had a diffuse smooth swelling in the neck of 10 cm by 6 cm in size, moved on swallowing and was consistent with goitre. There was no cervical lymphadenopathy. The rest of the examination was normal. Investigations revealed a TSH of 76.5 mIU/l, free T₄ of 2.2 pmol/l and a raised thyroid peroxidase antibody titres suggestive of autoimmune thyroid disease. Neck ultrasonography confirmed a diffusely enlarged thyroid. He was commenced on thyroxine and was discharged with follow-up. He represented 4 days later with left calf swelling. Examination showed a swollen, red, tender calf and investigations revealed an abnormal white cell count (>200×109/l) with blast cells. He was transferred to the oncology team and a bone marrow biopsy confirmed acute myeloid leukaemia. He was treated with chemotherapy and bone marrow transplantation. His thyroid function normalised together with resolution of the goitre within 4 weeks of starting thyroxine and chemotherapy. The patient is making good progress and remains on thyroxine replacement.

Conclusions: Autoimmune thyroid disease involves T-cell mediated targeting of thyroid antigen and the presence of thyroid gland enlargement in our patient suggests that myeloid leukaemic cells also have the capacity to migrate to the sites of autoimmune damage in the thyroid gland. Nodular and diffuse thyroid enlargement may reflect an underlying malignant process.