EP835 - ECE_3442 - Allergy to dexamethasone: a rare pitfall in endocrine practice

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Abstract Background Dexamethasone is widely used in endocrinology, particularly for diagnostic suppression tests. Hypersensitivity reactions to corticosteroids are rare, with a reported frequency ranging from 0.2% to 5%. This condition may represent both a diagnostic and therapeutic challenge. Case Presentation We report the case of a 55-year-old woman admitted to our department for evaluation of resistant hypertension evolving for six years, complicated with a left ventricular hypertrophy. Her medical history included type 2 diabetes treated with dual therapy, obesity (BMI: 39 kg/m2), and documented allergies to penicillin and paracetamol. Secondary causes of hypertension were investigated. Renal artery CT angiography excluded a renovascular cause. During the low-dose dexamethasone suppression test, the patient developed a mild acute urticarial reaction a few minutes after dexamethasone administration. The reaction persisted throughout the test, and resolved spontaneously afterward. Subsequent skin prick testing confirmed an allergy to both dexamethasone and betamethasone. As the dexamethasone suppression test was uninterpretable in this context, Cushing's syndrome was excluded using alternative screening methods: Late-night cortisol and 24-hour urinary free cortisol levels were normal. Further evaluation of contributing factors to resistant hypertension revealed severe obstructive sleep apnea syndrome (OSAS), confirmed by polysomnography. The patient was managed with lifestyle and dietary measures, GLP-1 receptor agonist therapy (semaglutide), and continuous positive airway pressure for OSAS. After six months of follow-up, she achieved a 7% weight loss, with good blood pressure control under dual therapy and improved glycemic control on GLP-1 therapy. Conclusions Corticosteroid allergy is a rare but clinically significant condition that can complicate endocrine diagnostic procedures. Alternative diagnostic strategies should be considered when evaluating hypercortisolism in patients with confirmed corticosteroid hypersensitivity. Late-night salivary cortisol or repeated urinary free cortisol may represent safe alternatives for Cushing's syndrome screening in these patients.

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