McCune–Albright syndrome and type 1 diabetes mellitus: a novel presentation

Abstract McCune–Albright syndrome (MAS) is caused by postzygotic somatic activating mutations of GNAS and is classically characterized by the clinical triad of peripheral precocious puberty, café‐au‐lait pigmentation, and polyostotic fibrous dysplasia. It can also present with other hyperfunctioning endocrinopathies, including growth hormone excess, hyperprolactinemia, hypercortisolemia, hyperthyroidism, and renal phosphate wasting due to excess fibroblast growth factor 23. We review the clinical, biochemical, radiological, and genetic findings in a 7‐year‐old girl diagnosed with MAS at age 4 and then with autoimmune type 1 diabetes mellitus at age 7. While MAS is associated with hyperglycemia secondary to growth hormone excess and hypercortisolemia, an association with diabetes mellitus has not been demonstrated. We review the unique presentation of a patient with these two rare conditions.