Mometasone Furoate–Induced Iatrogenic Cushing’s Syndrome and Secondary Adrenal Insufficiency: A Case Report

Intranasal corticosteroids (INCS) are widely used to treat allergic rhinitis and nasal obstruction. While their safety profile is generally well established, both local and systemic side effects can occur. While it is well-known that a chronic exposure to systemic glucocorticoid treatment could determine Cushing's syndrome (CS) and suppression of the hypothalamic-pituitary-adrenal (HPA) axis, there is less awareness when the administration is topical or intranasal. We report the case of an 8-year-old Caucasian girl who developed Cushingoid features following prolonged INCS treatment-initially with betamethasone and subsequently with mometasone furoate. Endocrine testing revealed undetectable baseline and after stimulation cortisol levels, suggesting a condition of adrenal insufficiency secondary to the prolonged glucocorticoid exogenous administration. Temporary hydrocortisone replacement therapy was required. Even if extremely rare, pediatricians should be aware that high-dose and long-term nasal steroid administration may cause iatrogenic CS, as well as systemic glucocorticoid treatment. Clinical features are characterized by the complications of glucocorticoid excess and by the potential life-threatening complications of adrenal insufficiency. Pediatric follow-up should be scheduled during the prolonged steroid treatment and at discontinuation, with prompt referral to a Pediatric Endocrinologist if signs and symptoms of CS (or adrenal insufficiency) are noticed.