A 36-day-old male infant was admitted to the intensive care unit (ICU) with severe lethargy, tachypnea, severe dehydration, 12% weight loss since birth, diarrhea, and fever (38 °C). His prenatal and birth history (term; birth weight, 3500 g) were unremarkable, and he exhibited normal male genital development. The biochemical measurements showed hyponatremia (Na, 126 mmol/L), normochloremia (Cl, 100 mmol/L), hyperkalemia (K, 10.8 mmol/L), and hypoglycemia (glucose, 50 mg/dL). He also had metabolic acidosis due to diarrhea. Arterial blood gas analysis showed a pH of 7.17, a carbon dioxide partial pressure of 24 mmHg (reference range: 35–45), and a bicarbonate concentration of 8.9 mEq/L (reference range: 22–26). The low plasma bicarbonate concentration of 8.9 mEq/L (15.1 mEq/L lower than normal levels) was associated with the reduced carbon dioxide partial pressure of approximately 24 mmHg. The patient was given 20 cc/kg of fluid with 5% dextrose, sodium chloride, and sodium bicarbonate for 1 h followed by maintenance fluid. Antibiotics (cefotaxime and gentamicin) were administered after a diagnosis of sepsis. After the initial interventions, his general condition seemed to be recovered, although hyponatremia and hyperkalemia persisted (Na, 128 mmol/L; K, 6.7 mmol/L). Further biochemical investigation showed an extremely high adrenocorticotropic hormone (ACTH) level (2000 pg/mL; reference range: 0–10.12 pmol/mL), high plasma renin activity (16.8 μg/mL/hr.; reference range: 0.32–1.84 μg/mL/hr) and a low aldosterone level (0.69 ng/dL; reference range: 2.0–110.0 ng/dL). He seemed to exhibit clinical decompensation after being in a highly fragile condition. A stressor (in the case, the infection) seemed to trigger an adrenal crisis. The patient’s karyotype was 46,XY. His 17-hydroxyprogesterone level (0.83 ng/mL; reference range: 0.7–2.5 ng/mL) and testosterone level (0.95 ng/mL; reference range: < 1.77 ng/ml) were normal, so we excluded congenital adrenal hyperplasia. The child was diagnosed with adrenal insufficiency and administered 6 mg of hydrocortisone and 0.1 mg of fludrocortisone (Florinef) once daily. His electrolyte imbalance and hypoglycemia were also corrected (arterial blood gas analysis: pH 7.34, PCO2 37 mmHg, HCO3 20 mmol/L; Na, 137 mmol/L; K, 5.7 mmol/L; glucose, 90 mg/dL). The patient was required to maintain glucocorticoid and mineralocorticoid treatment after discharge. We informed the patient’s parents that the glucocorticoid should be administered at an increased dose during stressful situations such as surgery, inflammation and trauma. Because his parents’ medication compliance was low, the patient was frequently hospitalized for adrenal crisis. At the age of 17 years, the patient showed no signs of puberty and had no axillary or pubic hair (Tanner stage 1). His basal gonadotropin levels were measured; the LH level was 0.40 mIU/mL, and the FSH level was 3.26 mIU/mL. A GnRH test (Relefact, 0.1 mg, Aventis Pharma, gonadorelin acetate) was performed, which showed prepubertal gonadotropin peak levels (LH 1.07 mU/mL, FSH, 3.58 mU/mL). These results, together with the lack of any sign of puberty, were consistent with the diagnosis of HH. The patient was given testosterone replacement therapy, which induced clinical signs of puberty, including a growth spurt. Other hormone levels were also tested. The results of the thyroid function test were in the normal ranges (T3 11.40 ng/dL, TSH 0.72 mIU/L, free T4 1.27 ng/dL). The growth hormone axis test results were also within normal ranges (insulin-like growth factor 1159.0 ng/mL;reference range: 57–426 ng/mL, basal growth hormone 0.26 ng/mL; reference range: 0.18–9.76 ng/mL). Abdominal computed tomography conducted at the time HH was diagnosed revealed severe atrophy of both adrenal glands. At the age of 24, the patient’s height was 180 cm (in approximately the 75th centile). He continued to have very low levels of arginine vasopressin (AVP, 1.47 pg/mL) and exhibited hypernatremia (146.1 mmol/L) and persistent strong thirst. He presented with polydipsia and polyuria (7 L/day), and his urinalysis showed low specific gravity (1.002) and low urine osmolarity (54 mOsm/kg H2O). Because his serum glucose and HbA1c levels were in the normal range, we ruled out diabetes mellitus. He underwent a water deprivation test, and the results revealed that the urine was not concentrated based on osmolality and that the urine output and serum sodium level were not changed, thus excluding primary polydipsia. We then conducted a vasopressin challenge test to check for central diabetes insipidus and found that the patient’s urine was five times more concentrated than normal according to osmolality. Subsequently, the patient was diagnosed with central diabetes insipidus. Magnetic resonance imaging showed a loss of signal in the posterior pituitary gland and an abnormal mass in the maxillary sinus. The signal changes in the posterior pituitary gland were consistent with central diabetes insipidus. After diagnosis, the symptoms were controlled with desmopressin spray (15 μg per dose twice a day). Because there has been no change in size, the left maxillary sinus mass is presumed to be a schwannoma and is being observed every 6 months without excision. We shared the diagnosis and treatment plan with the patient. An outside laboratory then conducted quantitative polymerase chain reaction (PCR) analysis to identify mutations in DAX1. PCR revealed that a base located at position 543 on gene DAX1, the causative gene of AHC, was deleted, which caused the 183rd amino acid, glycine, to be replaced with valine. This mutation was a frameshift mutation resulting in replacement of the 81st amino acid codon with a stop codon, which induced a loss of function. The initial sequencing results (at 17 years old) were misread, but our hospital’s molecular diagnostic team found the errors when they reread the PCR sequencing results. In summary, this male exhibited no genital abnormality at birth and was determined to be 46,XY with adrenal insufficiency, HH and central diabetes insipidus, consistent with the diagnosis of AHC, despite the unusual presence of diabetes insipidus. For maintenance, he was prescribed hydrocortisone, a mineralocorticoid and vasopressin.