Clinical and genetic heterogeneity of micronodular adrenal hyperplasia

Micronodular adrenal hyperplasia is a rare cause of ACTH-independent Cushing syndrome. It can be divided into two entities: primary pigmented nodular adrenocortical disease (PPNAD) and non-pigmented micronodular adrenocortical disease, among which familial and sporadic forms are distinguished. The most common is the genetically determined familial form PPNAD, as one of the components of Carney complex. The vast majority of patients have identifiable pathogenic variants in the PRKAR1A gene. In addition to the PRKAR1A gene mutations, inactivating mutations in the genes encoding phosphodiesterases (PDE11A4 and PDE8B), as well as PRKACA gene amplification, have been described in individuals with isolated forms. Despite the relative antiquity of the description of micronodular adrenal hyperplasia and the Carney comlex, a detailed study of pathophysiological mechanisms, genetic and clinical aspects of this pathology, nowadays, clinicians continue to face «atypical» cases. Thus, the nature of this disease is not well understood and requires further research. This review presents the accumulated data on micronodular adrenal hyperplasia, genetics aspects, and also describes 2 unique clinical cases of isolated PPNAD with unilateral adrenalectomy results.