Which clinical history findings are characteristic of McCune-Albright syndrome (MAS)?

Updated: Jan 17, 2019
  • Author: Gabriel I Uwaifo, MD; Chief Editor: George T Griffing, MD  more...
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Answer

Hyperthyroidism rarely occurs in MAS without several other features of the syndrome also being present. A family history of autoimmune thyroid disorders supports a diagnosis of Graves disease, though Graves disease can occur in the absence of a family history. If no other features of MAS are present, autoimmune thyroid disease is far more likely. In cases of unexplained hyperthyroidism, surreptitious administration of thyroid hormone should be considered; again, this explanation would be more likely in the absence of physical findings of MAS.

Infantile Cushing syndrome may initially be seen without other signs of MAS. Cortisol excess should be considered in any infant with profound failure to thrive, hypertension, muscle weakness, and easy bruising. Unlike older children with cortisol excess, infants may have decreased appetite and food intake.

In the absence of other signs of MAS, exogenously administered steroids should be considered before excess cortisol is attributed to an activating mutation of the alpha subunit of the stimulatory G protein (Gs alpha; GNAS1 gene). Injections of steroids can be long-lasting; triamcinolone acetonide has caused Cushing syndrome for well over 1 year after the final injection, presumably as a result of an inability to metabolize and excrete the steroid.

Growth hormone (GH) excess coexisting with MAS is uncommon and generally is not found until early adulthood or mid-adulthood. Patients with MAS and GH excess present with the same paradoxic responses as regular patients with acromegaly upon thyrotropin-releasing hormone stimulation and upon oral glucose tolerance tests.

Associated hypogonadotropic hypogonadism may be present, particularly in the setting of hyperprolactinemia. Hyperprolactinemia in the absence of acromegaly has not been described in patients with MAS.

Rarely, MAS has been associated with high-output congestive heart failure similar to that seen in Paget disease.


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