LAUSR

Abstract Objectives We intend to describe a case of McCune-Albright Syndrome (MAS), a rare disease characterized by fibrous dysplasia (FD), cutaneous hyperpigmentation and hyperfunctioning endocrinopathies (HFE). Case presentation We report the case of a 13-year-old male child who presented with a café-au-lait macule in the lumbosacral region and disabling polyostotic FD, requiring several surgical interventions and bisphosphonates from the age of 3 years (Y) + 9 months (M) due to persistent and severe pain. Hyperthyroidism (HT) became apparent at 5 Y + 1 M with a T3/T4 ratio greater than 20. Treatment with anti-thyroid drugs (ATD) was carried out for 7 Y and there was a progressive improvement in pain complaints 8 M after starting ATD, allowing treatment with pamidronate to be discontinued. Total thyroidectomy was performed at 12 Y + 5 M. Conclusions This is a case of MAS-associated HT that reflects the deleterious effect of thyroid hormone excess on FD, reinforcing the need of having a low threshold for suspicion of HFE that may arise.