A 10–month old baby previously normal, suddenly becomes distressed in his crib. The external appearance of genitalia was normal, except hyperpigmentation. lood glucose showed a level of 30 mg%. What is the most probable diagnosis ?

Familial glucocorticoid deficiency : Familial glucocorticoid deficiency is a rare autosomal recessive condition. It is characterized by adrenal insufficiency. The pathological examination of the adrenal gland reveals that :- Zona glomerulosa ---> well preserved. Zona fasciculata ---> atrophied. Zona reticularis  ---> atrophied. This causes low cortisol concentration because the zona fasciculata is primarily responsible for glucocorticoid production. Because the zona glomerulosa is well preserved mineralocorticoid action is usually unaffected. Low circulating serum cortisol results in lack of feedback inhibition to the hypothalamus which results in increased ACTH secretion from pituitary. Clinical features : Patients with familial glucocorticoid deficiency generally presents with signs and symptoms of adrenal insufficiency with the important distinction that mineralocorticoid production is always normal. The most common initial presenting sign is deep hyperpigmentation of the skin, mucous membrane or both as a result of the action of adrenocorticotrophic hormone (ACTH) on cutaneous melanocyte stimulating hormone (MSH) receptors. The symptoms are compatible with glucocorticoid deficiency. Many patients presents with recurrent hypoglycemia or severe infections. In the neonatal period, frequent presenting signs include - feeding problems, failure to thrive, regurgitation and hypoglycemia manifesting as seizures.