Abstract #1405991: Graves’ Disease Presenting as Thymic Hyperplasia

Abstract

Thymic hyperplasia associated with Graves' disease (GD) is well known to thyroidologist, and reported up to 38% of GD worldwide; however, it remains unrecognized in routine clinical practice. Here we report two cases of GD presenting as anterior mediastinum mass, consistent with thymic hyperplasia. I - A 41-year-old female presented with shortness of breath, chest pain, and nausea. She reported palpitations and unintentional weight loss over the last six months. There was no history of thyroid disease. Blood pressure was 162/86 mmHg, heart rate 94/minute, respiratory rate 26 breaths/minute, temperature 36.7 F, and body mass index 23.5 kg/m2. The thyroid was enlarged with mild tenderness. Laboratory showed TSH < 0.005 (0.358 to 3.74 mc IU/mL), free thyroxine 5.54 (0.76 to 1.46 ng/dL), thyroid-stimulating immunoglobulins 407% (0 to 140%). Computed tomography of the chest with contrast revealed an anterior mediastinal mass. GD was diagnosed, and she was started on standard therapy. II - A 54-year-old female presented with worsening shortness of breath, palpitations, and leg swelling for a several weeks. She reported progressive exertional shortness of breath for ten months, intermittent palpitations, fatigue, and weight loss for the last five months. She had a history of hypertension but no history of thyroid disease. At presentation blood pressure was 159/72 mm Hg, heart rate 102 beats/minute, respiratory rate 20/minute, temperature 37.1 F, and body mass index 32.7 kg/m2. She had atrial fibrillation with a rapid ventricular rate. Her examination showed mild bilateral proptosis and non-tender enlarged thyroid. Results showed TSH < 0.005 (0.358 to 3.74 mc IU/mL), free thyroxine 7.23 (0.76 to 1.46 ng/dL), free triiodothyronine 13.2 (2.18 to 3.98 pg/mL), anti-microsomal antibody (TPO) 315 (0 to 60 IU/mL), and thyroid-stimulating immunoglobulins (TSI) 429 (0 to 140%). Computed tomography of the chest with contrast revealed an anterior mediastinal mass. GD was diagnosed, and standard therapy was started. Discussion: Our two cases demonstrate GD-associated thymic hyperplasia later confirmed during hospitalization with MRI imaging. CT-imaging results were available at the same time or earlier than thyroid function tests but did not mention the differential diagnosis of GD or other autoimmune diseases which would help to avoid unnecessary interventions and guide therapy. Both patients were schedule to closely follow up with endocrinology and repeat imaging in about six months to one year is expected to show reduction in thymic size which would support the diagnosis of GD-associated hyperplasia.