ESPE Abstracts

Introduction: McCune Albright syndrome (MAS) is a rare genetic disorder characterized by a triad of hyperpigmentation, endocrinopathies, and fibrous dysplasia (FD), caused by post-zygotic somatic mutations. Hyperthyroidism is the second most common endocrinopathy in MAS and poses significant management challenges in infants.

Case History: 7-month-old infant girl born to non-consanguineous parents, who presented with per vaginal bleeding and breast development. She exhibited excessive sweating since birth, along with rapid weight gain and height acceleration over the past 2-3 months. Physical examination revealed extensive café-au-lait spots, tachycardia, and elevated blood pressure. Pubertal examination indicated stage 2 breast development without axillary and pubic hair. Investigations confirmed gonadotrophin-independent puberty, thyrotoxicosis, with high levels of 8 am cortisol and ACTH following ODST. Gonadotrophin independent puberty was treated with letrozole 1.25 mg/ daily an aromatase inhibitor. Treatment with carbimazole (0.75 mg/kg/day) initially led to neutropenia, necessitating a switch to Lugol's iodine, which successfully resolved the thyrotoxicosis and neutropenia within 10 days. Cortisol normalized when thyrotoxicosis became under control. carbimazole was then reintroduced and increased to 1 mg/kg/day. Patient currently maintains normal development with controlled thyrotoxicosis on a reduced dose (0.5 mg/kg/day) of carbimazole. MRI pituitary was normal with sphenoid bone FD.

Discussion: MAS can be complicated with fibrous dysplasia and multiple endocrinopathies. Early onset Cushing syndrome and Cushing diseases are difficult to manage with high mortality. Peripheral precocious puberty treated in females with aromatase inhibitors and in males with aromatase inhibitors and anti-androgens. FD can lead to deformities, bone pain and fractures. Dysplastic bones can lead to FGF 23 mediated hypophosphaturia which need phosphate replacement. Early-onset hyperthyroidism in MAS typically requires surgical intervention by experienced surgeons Our case demonstrates successful management with higher doses of carbimazole in infants, leading to controlled thyrotoxicosis without the need for immediate surgery. Nevertheless, definitive surgical intervention may still be necessary in the future.