Endocrine Abstracts

Introduction: Ophthalmopathy and dermatopathy are the most frequent manifestations of Graves Disease (GD). It is also known the relation between GD and other autoimmune diseases like myasthenia gravis. Thymus hyperplasia in GD is already documented on literature but it’s mechanism is not well understood. There are two possible explanations, one related to thyrotrophin receptors stimulation present on thymus, and other related to tissue stimulation due to generalized hyperplasia from lymphoid system. On the other hand, the association between hyperthyroidism and pericarditis, although rare, has been described before. However, aetiology remains unknown. There is only one case reported, describing the association between GD, pericarditis and thymus hyperplasia.

Clinical Case: 22 years old, healthy man attended endocrinology department at February 2017 with symptoms of hyperthyroidism. Laboratory evaluation revealed TSH<0.1 mUI/l (0.45–4.5mUI/l), FT4 3.87 ng/dl (0.79–1.76 ng/dl), anti-thyroid peroxidase antibodies 663 UI/l and anti-thyrotropin receptor antibodies (TRABs) 15.6 UI/l (both positive), and anti-acethylcholine antibodies were negative. After diagnosis of hyperthyroidism, he started therapy with methimazole and propanolol. Five months later, he was admitted at the ER, complaining from fever and pre-cordial pain. The electrocardiogram showed acute pericarditis, although without effusion or suggestive image on the echocardiogram, reason why he performed a TC scan. TC revealed an anterior homogeneous mediastinum mass with 39×20 mm, compatible with thymus hyperplasia. After observation by a cardio-thoracic surgeon, he had indication to maintain GD therapy and imaging re-evaluation in 3 months.

Discussion: This case reveals a coexistence of pericarditis and thymus hyperplasia in a patient with GD. In the presence of mediastinum mass with benign features (homogeneous mass, defined outlines, without calcifications and without invasion of fat or pleura nor cystic component) and if concomitant GD, the hypothesis of thymus hyperplasia should prevail. It is also known the regression of thymus volume during hyperthyroidism treatment. Therefore, in the presence of a benign criteria mediastinum mass, invasive diagnostic exams should be delayed while hyperthyroidism treatment is under way, however, imaging control of the mass should be maintained. Rare cases exist reporting pericarditis as a severe hyperthyroidism complication and therefore, its aetiology remains unexplained. The relation between pericarditis and thymus hyperplasia, also described, may be due to, proximity of the hyperplasic thymus tissue to the moving pericardium, resulting in inflammation. The nature and the comprehension of the coexistence of these three entities described, remains unknown, lacking more similar clinical cases for their understanding.