The Differential Diagnosis between Cushing's Disease and Pseudocushing Syndrome in a Pre-agonic Patient.

BACKGROUND: The pseudo-Cushing's encompass several disorders that can occur in high-stress situations and that show biochemical features like those of Cushing's syndrome. We present a case with difficult differential diagnosis for overlapping laboratory findings.

CASE REPORT: A 74-year-old man was admitted to our hospital for worsening dyspnoea for a month, 15 kilograms of weight loss in the previous months, asthenia, hypotonia, and muscle hypotrophy. Moreover, due to the onset of acute hypoxic-hypercapnic respiratory failure, the patient was treated with non-invasive ventilation and then admitted to the intensive care unit, for pneumonia and respiratory failure due to Meticillin-sensitive Staphylococcus aureus and Klebsiella Aerogenes. Antibiotic therapy was started. During the treatment in the ICU, the patient underwent endotracheal intubation for the worsening of respiratory function, and inotropic drug therapy was introduced for the development of septic shock. Hormones were tested, showing an ACTH-dependent hypercortisolism. The results of Nugent, Liddle, and the dexamethasone- suppressed CRH stimulation tests suggested a not-neoplastic ACTH-dependent hypercortisolism. The pituitary contrasted magnetic resonance image showed gland hypertrophy, and the abdominal computed tomography ruled out adrenal lesions. Unfortunately, the patient developed a multi-organ failure and died. The autopsy finding confirmed the absence of pituitary and other neuroendocrine tumors and showed bilateral adrenal hypotrophy.

CONCLUSION: Our clinical case described a patient with pseudo-Cushing's syndrome during sepsis and pre-agonist phase, with a difficult differential diagnosis, in which the combination of the low-dose dexamethasone suppression test and the CRH test allowed a conclusive and correct diagnostic orientation.