A serious and unusual presentation of congenital isolated ACTH deficiency due to TBX19 mutation, beyond the neonatal period

Summary Congenital isolated adrenocorticotrophic hormone (ACTH) deficiency due to T-box transcription factor-19 (TBX19 mutation) (MIM 201400; ORPHA 199296) usually presents in the neonatal period with severe hypoglycemia, seizures, and sometimes prolonged cholestatic jaundice. We report a case with an unusual presentation that delayed the diagnosis. A 9-month-old female patient with no relevant personal history was admitted to the emergency department due to a hypoglycemic seizure in the context of acute gastroenteritis. There was rapid recovery after glucose administration. At age 4, she presented with tonic-clonic seizures, fever, and gastrointestinal symptoms and came to need support in an intensive care unit. Low serum cortisol was documented and hydrocortisone was initiated. After normalization of inflammatory parameters, the patient was discharged with hydrocortisone. The genetic investigation was requested and compound heterozygous mutations in TBX19 were detected. This is a rare case of presentation of TBX19 mutation outside the neonatal period and in the setting of acute disease, which presented a diagnostic challenge. Learning points Congenital isolated adrenocorticotrophic hormone deficiency due to TBX19 mutation usually presents with neonatal hypoglycemia and prolonged cholestatic jaundice. An uneventful neonatal period, however, does not exclude the diagnosis as the disease may be asymptomatic at this stage. In the context of idiopathic hypoglycemia, even in the context of acute disease, hypocortisolism must always be excluded. Genetic evaluation should be performed in cases of congenital central hypocortisolism to allow proper counselling.