A previously healthy 6 week old female infant, is found unresponsive in on the bed. In the emergency depament, she is noted to be well developed and well nourished with normal blood pressure and appearance of the genitalia but with increased pigmentation of her skin. Her blood glucose level is 30 mg/dL. What is the most likely diagnosis?

Infant is showing features of familial glucocoicoid deficiency a rare autosomal recessive disorder characterized by primary adrenal insufficiency without mineralocoicoid deficiency. In this condition there is adrenocoical resistance to ACTH. Patients presents during early infancy with hypoglycemia, hyperpigmentation, low plasma coisol and failure to respond to ACTH stimulation with increased steroidogenesis. Zona fasciculate and reticularis in these patients are reduced to a narrow band of fibrous tissue whereas the zona glomerulosa is well preserved. Patients are treated with replacement doses of hydrocoisone or equivalent doses of other glucocoicoids. They do not require mineralocoicoid supplementation as their zona glomerulosa is normal.