A case of silent 21‐hydroxylase deficiency with persistent adrenal insufficiency after removal of an adrenal incidentaloma

A case of an adrenal incidentaloma in a 57‐year‐old man with silent 21‐hydroxylase deficiency is reported. Abdominal computed tomography revealed a right adrenal tumour of 6cm in diameter. There was no evidence of adrenal hormone excess. However, after surgical removal of the adrenal tumour, the patient developed acute adrenal insufficiency. Adrenocortical function has remained low ever since surgery. Pathological examination of the tumour revealed a cortical adenoma. On the basis of increased plasma renin activity and serum 17α‐hydroxyprogesterone concentration and decreased 21‐hydroxylase activity of the adenoma tissue, the patient was diagnosed as having systemic 21‐hydroxylase deficiency. There are two possible mechanisms for the persistent adrenal insufficiency; first the residual left adrenal gland may have been originally hypo‐functioning for some reason and, second, the left gland may have lost the ability to regenerate following prolonged suppression by the adenoma. In cases of adrenal incidentalomas with 21‐hydroxylase deficiency, the indications for surgical removal should be carefully considered.