Pyrexia of Unknown Origin due to Secondary Adrenal Insufficiency: A Case Report

Abstract

Adrenal insufficiency is a critical condition that can often present with non specific symptoms, posing a diagnostic challenge in the context of co-existing conditions. Authors hereby, report a complex case of secondary adrenal insufficiency revealed through persistent fever and hyponatremia in a 73-year-old female with a multifaceted medical history, including hypertension, diabetes, and Takotsubo cardiomyopathy. Her symptoms of intermittent fever and diarrhoea were refractory to treatment, leading to hospital readmission. Initial laboratory investigations highlighted hyponatremia, low haemoglobin, elevated inflammatory markers, and low cortisol levels. Although a urinary tract infection with multidrug-resistant Klebsiella was identified and treated, her febrile state persisted. Extensive serological testing for a broad range of infectious diseases yielded negative results, excluding infectious etiologies as the cause of her fever. Imaging studies, including chest X-ray, Electrocardiogram (ECG), echocardiogram, Positron Emission Tomography (PET) scan, Computed Tomography (CT), and transesophageal echocardiography, failed to identify a source of infection or malignancy. Notably, a low random cortisol level coupled with an inappropriately low Adrenocorticotropic Hormone (ACTH) level prompted further endocrine evaluation. Magnetic Resonance Imaging (MRI) revealed an empty sella turcica, confirming secondary adrenal insufficiency. This diagnosis was substantiated by the patient’s positive response to steroid therapy, which led to clinical improvement and eventual discharge. The present case underlines the importance of considering adrenal insufficiency in patients presenting with unexplained hyponatremia and fever, particularly when other common aetiologies have been ruled out. It also illustrates the potential for critical endocrine disorders to mimic sepsis, underscoring the necessity of a comprehensive diagnostic approach in the face of complex presentations.