PRKAR1A and primary pigmented nodular adrenocortical disease: This pathway was further implicated in the development of CS due to primary pigmented nodular adrenocortical disease (PPNAD) through the study of another rare familial tumor syndrome, Carney complex (CNC), that is predominantly due to germline inactivating defects in PRKAR1A, which encodes the regulatory subunit type 1α (R1α) of PKA (3).