Objective: McCune-Albright syndrome (MAS) is a mosaic disease arising from early embryonic somatic activating mutations of GNAS, which encodes the 3 <=, 5 <=-cyclic adenosine monophosphate (cAMP) pathway-associated G-protein, Gs . Constitutive activation of Gs leads to increased cAMP signaling in brain, as well as in peripheral organs, particularly bones. Although subjects with MAS show psychiatric and neurological symptoms, few studies have attempted to assess brain changes in these individuals. This protocol seeks to study changes in the cAMP cascade both in brain and peripheral organs of individuals with MAS using [11C](R)-rolipram PET, which binds to phosphodiesterase 4 (PDE4) and reflects cAMP cascade activity.