From MedlinePlus Genetics
There are multiple types of familial glucocorticoid deficiency, which are distinguished by their genetic cause.

A shortage of adrenal hormones (adrenal insufficiency) causes the signs and symptoms of familial glucocorticoid deficiency. These signs and symptoms often begin in infancy or early childhood. Most affected children first develop low blood glucose (hypoglycemia). These hypoglycemic children can fail to grow and gain weight at the expected rate (failure to thrive). If left untreated, hypoglycemia can lead to seizures, learning difficulties, and other neurological problems. Hypoglycemia that is left untreated for prolonged periods can lead to neurological damage and death. Other features of familial glucocorticoid deficiency can include recurrent infections and skin coloring darker than that of other family members (hyperpigmentation).

Familial glucocorticoid deficiency is a condition that occurs when the adrenal glands, which are hormone-producing glands located on top of each kidney, do not produce certain hormones called glucocorticoids. These hormones, which include cortisol and corticosterone, aid in immune system function, play a role in maintaining normal blood sugar (glucose) levels, help trigger nerve cell signaling in the brain, and serve many other purposes in the body.  https://medlineplus.gov/genetics/condition/familial-glucocorticoid-deficiency