Simultaneous Thyroid Autoimmunity: A Coexistence of Grave's Disease and Hashimoto's Thyroiditis

Introduction: Grave’s Disease (GD) and Hashimoto's Thyroiditis (HT) are two autoimmune diseases whose coexistence is rare. We report a case of a patient in whom both diseases manifested simultaneously. Case report: A 36- year-old woman presented with thyrotoxicosis. She had tachycardia with WHO grade 2 homogeneously non-pulsatile goiter, without exophthalmos. The evaluation revealed peripheral hyperthyroidism with positive anti-thyroid peroxidase (anti-TPO) antibodies and anti-thyroid-stimulating hormone receptor (anti-TSHR) antibodies. Cervical ultrasound revealed a goiter affecting the right lobe in the context of thyroiditis. Thyroid scintigraphy indicated a picture suggestive of Graves' disease in the left lobe and hypocaptating thyroiditis in the right lobe. The patient was treated with propranolol and Carbimazole, with alternating phases of hyperthyroidism and hypothyroidism. Discussion and Conclusion: Autoimmune thyroid diseases, GD and HT, are specific to the thyroid gland and are common in women. They share pathogenic features that could explain their association, including genetic and environmental factors leading to thyroid cell damage, T-cell-mediated autoimmunity, human leukocyte antigen binding, and the presence of autoantibodies such as anti-thyroid peroxidase antibodies in GD. Rare cases have demonstrated that HT can manifest after GD, and vice versa, leading to an alternation of hyperthyroidism and hypothyroidism in certain patients due to changes in the balance between various categories of antibodies. In the present case, the patient simultaneously presented both diseases.