Update on primary micronodular bilateral adrenocortical diseases.

Purpose Of Review: Primary micronodular bilateral adrenocortical hyperplasias (MiBAH) are rare challenging diseases. Important progress in understanding its pathophysiology and genetics occurred in the last two decades. We summarize those progress and recent data on investigation and therapy of MiBAH focusing on primary pigmented nodular adrenocortical disease (PPNAD).

Recent Findings: Larger recent cohorts of PPNAD patients from various countries have confirmed their variable Cushing's syndrome phenotypes. Age of onset is earlier than other ACTH-independent Cushing's syndrome causes and the youngest case have now occurred at 15 months. Two retrospective studies identified an increased risk of osteoporotic fractures in PPNAD as compared with other Cushing's syndrome causes. The utility of 6-day oral dexamethasone test to produce a paradoxical increase of urinary-free cortisol in PPNAD was confirmed but the mean fold of increase was of 48%, less than previously suggested. Several new genetic variants of the PRKAR1A gene have been reported in PPNAD or Carney complex (CNC). Remission of Cushing's syndrome with unilateral adrenalectomy was reported in a few patients with PPNAD.

Summary: MiBAH, PPNAD and CNC are rare challenging diseases, but with combined expert clinical and genetic approaches a comprehensive investigation and prevention strategy can be offered to affected patients and families.