POMC and autosomal dominant cerebellar ataxia: Approximately 6% of all NFPAs are silent corticotroph adenomas (SCA),18 that is, pituitary adenomas with positive immunoreactivity for ACTH but without any signs or symptoms of Cushing syndrome; plasma ACTH concentrations are usually normal.19 In the setting of a lack of clinical or biochemical manifestations of hypercortisolism, differentiating between NFPAs and SCAs relies on histopathologic evidence of ACTH secretion.20