Introduction: The coexistence of autoimmune thyroid disease and type 1 diabetes mellitus is well established; however, their sequential or concurrent presentation in very young children remains uncommon. We demonstrate two paediatric cases with concurrent Graves' disease and type 1 diabetes mellitus, each illustrating distinct complications and clinical courses. Cases: A 3-year-old female presented with anterior neck swelling, weight loss, and persistent tachycardia. Biochemical evaluation confirmed severe thyrotoxicosis (T4 152.3 pmol/L, TSH <0.008 mIU/L) with markedly elevated antithyroglobulin and anti–thyroid peroxidase antibodies. Thyroid ultrasonography demonstrated a diffusely enlarged, hypervascular gland with nodular changes, consistent with Graves’ disease. During longitudinal follow-up, she developed polyuria, polydipsia, and hyperglycemia, with positive pancreatic autoantibodies confirming type 1 diabetes mellitus. Notably, serial early morning cortisol measurements were persistently low, raising concern for evolving adrenal insufficiency and suspicion of autoimmune polyglandular syndrome type 2. Comprehensive endocrine evaluation is ongoing. A 4-year-old male presented with a 1-year history of recurrent self-limiting fever followed by significant fatigability for 1 month. Salient examination on admission revealed tachycardia, anterior neck swelling, and an incidental pansystolic murmur. Thyroid function tests confirmed thyrotoxicosis (T4 38.6 pmol/L, TSH <0.008 mIU/L). Serial serum glucose was markedly elevated on admission, prompting further testing that confirmed type 1 diabetes mellitus with positive pancreatic autoantibodies. Echocardiography demonstrated moderate-to-severe mitral regurgitation with heart failure secondary to prolonged uncontrolled hyperthyroidism state. Cardiac function improved with restoration of a euthyroid state, highlighting the reversible nature of thyrotoxic heart failure. Conclusion These cases highlight the progressive nature of childhood autoimmunity, where Graves’ disease may precede the development of type 1 diabetes mellitus and evolving features of autoimmune polyglandular syndrome type 2. They further emphasize that thyrotoxic heart failure is potentially reversible with restoration of a euthyroid state, underscoring the importance of early recognition and vigilant long-term surveillance.
Diabetes Mellitus, Type 1 ; Graves Disease ; Heart Failure ; Diabetes Mellitus, Type 2