Nephrogenic diabetes insipidus as the first manifestation of Ectopic ACTH syndrome in a HIV infected patient

The Ectopic Adrenocorticotrophic Hormone (ACTH) Syndrome (EAS) is a high mortality paraneoplastic syndrome, which represents 10-15% of Cushing Syndromes (CS). Around 70% of tumors are located in the chest, neck or adrenals. It frequently has atypical manifestations, leading to delay in diagnosis. Here, we report a particular case of EAS manifested predominantly by nephrogenic diabetes insipidus (NDI). A 48 years old man, HIV infected, was admitted with polyuria, polidipsia and lower limb weakness. He had hipertension, crackles in the right hemithorax and linphanedophathy. Laboratory assessments showed hyperglycemia, hypernatremia, severe hypocalemia, metabolic alkalosis and low urinary osmolarity, which persisted after water deprivation test and desmopressin administration, characterizing a NDI. Chest images showed a lung tumor, which, in conjunction with the clinical and laboratorial picture lead to the suspicion of EAS. Cortisol levels after dexametasona were 143μg/dL and serum ACTH was 630pg/mL. Pituitary was normal and adrenals showed bilateral hyperplasia. Lymph node biopsy revealed a neuroendocrine tumor with positive immunohistochemistry for ACTH. Patient died a few days later due to nosocomial pneumonia. The EAS can be associated with very high cortisol levels, which evolves rapidly, resulting in the absence of typical features of CS. The knowledge of the different clinical presentations is essential to establish prompt diagnostic and support. This syndrome has to be considered in patients with a neoplasm and diabetes insipidus, especially if accompanied by signs of excess of mineralocorticoid action. Although the ideal treatment is excision of the tumor, adrenolitic drugs may help to reduce complications and improve survival.