POMC and familial glucocorticoid deficiency: Familial glucocorticoid deficiency (FDG), which is also known as familial glucocorticoid insufficiency, hereditary adrenocortical unresponsiveness to ACTH, and familial Addison’s disease, is a rare, early onset, autosomal recessive disorder characterized by low or undetectable plasma cortisol levels, normal mineralocorticoid levels, excess plasma ACTH, and hypoplasia of adrenal cortex zona fasciculata and zona reticularis.