PET Imaging of Phosphodiesterase-4 (PDE4) in Brain and Peripheral Organs of McCune-Albright Syndrome

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.

Study population: Participants will include 20 subjects with MAS and 15 healthy subjects group-matched to MAS subjects for age and gender. Both MAS subjects and healthy controls will have one or two PET scans: one whole body and one brain scan. We expect about 10 brain and 10 whole body scan to be performed in each group.

Design: Subjects with MAS will be recruited from participants in 98-D-0145 Screening and Natural History of Patients with Polyostotic Fibrous Dysplasia and the McCune-Albright Syndrome (PI: Alison M. Boyce, MD). Only participants in protocol (98-D-0145) who provided self-consent without a legally authorized representative will be recruited. Brain PET scans will be performed by measuring metabolite-corrected arterial input function. No venous blood sampling will be performed for whole body scans.

Outcome measures: The primary outcome measure will be obtained in brain scans as the amount of radioligand binding quantified as distribution volume (Vt). Calculated from both brain and plasma data, Vt reflects rolipram binding to PDE4, corrected for any individual differences in metabolism of the radioligand or regional blood flow in brain. The secondary outcome measure will be obtained in whole body scans as area under the curve (AUC) of radioactivity expressed as standard uptake value (SUV). SUV is calculated by normalizing radioactivity in PET images to injection activity and body weight. Vt in brain will be compared between subjects with MAS and healthy controls. AUC will be compared within-subjects with MAS between areas of craniofacial fibrous dysplasia and adjacent unaffected bone. AUC of whole body scans will also be compared between subjects with MAS and healthy controls. We hypothesize that subjects with MAS will show greater rolipram binding than healthy controls in brain regions, as well as greater rolipram uptake in bones affected by fibrous dysplasia than in unaffected bones.

• INCLUSION CRITERIA:

Subjects with MAS:

• At least 18 years of age
• Able to provide self-consent
• Diagnosed with MAS under 98-D-0145.
• Have craniofacial fibrous dysplasia

Healthy Subjects:

• At least 18 years of age.
• Healthy based on medical history and physical examination.

Exclusion criteria

Subjects with MAS:

• Serious medical conditions, which may interfere with study procedures. Such conditions include but not limited to significant bone abnormalities in wrist areas of both arms, which makes it difficult to place a radial arterial line, clinically marked dysfunction of liver or kidney, which may delay clearance of [(11)C](R)-rolipram.
• Clinically significant laboratory abnormalities not linked to endocrine abnormalities but that may interfere with the PET measurement or affect safety of the participant during this study.
• Positive HIV test.
• Head trauma resulting in a period of unconsciousness lasting longer than one hour.
• Metallic foreign bodies that would be affected by the magnetic resonance imaging (MRI) magnet, or fear of enclosed spaces likely to make the subject unable to undergo an MRI scan.
• Recent research-related exposure to radiation (i.e., PET from other research) that, when combined with this study, would be above the allowable limits.
• Inability to lie flat on camera bed for about two and a half hours.
• Pregnancy or breastfeeding.
• NIMH employees/staff and their immediate family members will be excluded from the study per NIMH policy.

Healthy Subjects:

• Serious medical conditions, which may interfere with study procedures. Such conditions include but not limited to clinically marked dysfunction of liver or kidney, which may delay clearance of [(11)C](R)-rolipram.
• Clinically significant laboratory abnormalities that may interfere with the PET measurement or affect safety of the participant during this study.
• Personal history of any DSM Axis I disorder.
• Positive HIV test.
• Head trauma resulting in a period of unconsciousness lasting longer than one hour.
• Metallic foreign bodies that would be affected by the MRI magnet, or fear of enclosed spaces likely to make the subject unable to undergo an MRI scan.
• Recent research-related exposure to radiation (i.e., PET from other research) that, when combined with this study, would be above the allowable limits.
• Inability to lie flat on camera bed for about two and a half hours.
• Pregnancy or breastfeeding.
• Current substance use disorder based on DSM.
• NIMH employees/staff and their immediate family members will be excluded from the study per NIMH policy.