SAT-369 Marine-Lenhart Syndrome: Case Report

Abstract Disclosure: M.A. Alvarez Castillo: None. INTRODUCTION: The coexistence of Graves' disease and nodules can occur in 35% of patients and in 0.8-2.7% of cases these are hyperfunctioning adenomas (HA); this combination has been called Marine-Lenhart syndrome (MLS). OBJECTIVE: Report a case of MLS. CLINICAL CASE: A 46-year-old female presented with increase in neck volume accompanied by compressive symptoms, insomnia, palpitations, sweating, tremor, hair loss and fatigue. When evaluated, clinically hyperthyroid with TSH 0.02 TT3 4.82 TT4 17.73 Ab TPO 13.1 Ab TG 310.5 TRab 22.94 and neck US showed heterogeneous parenchyma of left thyroid lobe (LTL) with type 3 vascular pattern and ITA 62.15 and right thyroid lobe (RTL) with 2 nodules, both TIR 4, the upper pole with increase of peripheral and central vascularity, with volume 12 ml. FNAB of both right thyroid nodules (RTN) was performed with results of Bethesda II. Thiamazole 30 mg/d and propranolol 20 mg/d were started. Percutaneous ablation of RTN was performed with 3% polidocanol 2 ml plus ethanol 1.5 ml and 8 mg intrathyroidal dexamethasone was administered in LTL. The procedure was carried out on 3 occasions with an interval of 2 months. Patient at follow-up, clinically euthyroid, denying compressive symptoms in the neck, TSH 1.16 FT4 1.25 TT3 0.95 and neck US in LTL with type 1 vascular pattern and ITA 24 and RTN with scarce peripheral vascularity and volume 7 ml, thiamazole 2.5 mg/d DISCUSSION: MLS is rare, so the diagnostic criteria are not yet well established, but thyroid function tests compatible with Graves' disease and imaging studies such as a thyroid scan demonstrating a diffuse increase uptake in thyroid parenchyma and markedly increased uptake in the affected nodules and US with increased vascularity and thyroid nodularity, have been considered. Treatment modalities have not been well demonstrated, so management with antithyroids, radioactive iodine, and surgery has been practiced. In this case, given our experience and considering the autoimmune origin of the disease, dexamethasone was administered in LTL and using minimally invasive techniques, the HA of RTL was sclerosed, thereby achieving euthyroidism and reduction of 58% of the nodule. CONCLUSION: MLS is rare, but given the nature of the pathology, minimally invasive techniques can be implemented in its management combined with antithyroids to increase therapeutic efficacy. Presentation: Saturday, July 12, 2025