Pericardial Effusion as a Presenting Symptom of Hashimoto Thyroiditis: A Case Report

Background: Hashimoto thyroiditis (HT) is the most frequent cause of acquired hypothyroidism in paediatrics. HT is usually diagnosed in older children and adolescents, mainly in females and is rare in infants and toddlers with cardiac involvement, including pericardial effusion, that can be found in 10% to 30% of adult HT cases. In this paper, a child with HT and pericardial effusion as the most important sign of HT is described. Case presentation: A four-year-old male child suffering for a few months from recurrent abdominal pain sometimes associated with vomiting underwent an abdominal ultrasound scan outside the hospital. This led to the identification of a significant pericardial effusion. At admission, his family history revealed that both his mother and maternal grandmother suffered from HT and that both were treated with l-thyroxine (LT4). The clinical examination did not reveal any pathological signs other than a palpable thyroid. His weight was 21 kg (78th percentile), his height was 101.8 cm (12th percentile) and his body max index (BMI) was 20.26 (96th percentile). On a chest radiograph, his heart had a globular appearance and the lung fields were normal. An echocardiography confirmed and determined the effusion amount (max, 23 mm; 600 mL) with light impairment of the heart kinetics. The ECG showed sinus bradycardia with a normal ST tract. Based on the blood test results, an infectious cause of the pericardial fluid excess was considered unlikely. Thyroid function testing revealed very high thyrotropin (TSH, 487 μIU/mL; normal range, 0.340–5.600 μIU/mL) and low serum-free thyroxine (fT4, 0.04 ng/dL; normal range, 0.54–1.24 ng/dL) levels. High thyroid peroxidase antibody titres in the blood were evidenced (>1500 UI/L; normal values, 0.0–9.0 UI/L). The thyroid ultrasound was consistent with thyroiditis. HT was diagnosed, and LT4 replacement therapy with levothyroxine sodium 1.78 µg/kg/die was initiated, with a gradual increase of the administered dose. The treatment was successful because a complete regression of the effusion after one month was evidenced, with a substantial modification towards normality of the thyroid function tests. One year later, the substitutive therapy led to complete normalization of the thyroid function indexes. A slight reduction of weight (BMI, 17.60 for age) and an increase of the velocity of height growth were evidenced. Conclusions: When fluid is identified in the pericardial space and pericarditis of unknown origin is diagnosed, the thyroid function should be immediately evaluated to prescribe substitutive hormonal therapy if necessary and thereby avoid overt hypothyroidism development and the risk of cardiac tamponade.