Syndrome of Inappropriate Antidiuretic Hormone Developing in Pulmonary Tuberculosis

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Pulmonary tuberculosis (PTB) is one of the common illnesses in developing countries, which can present with various clinical manifestations. It is one of the rare pulmonary infections causing hyponatraemia through several mechanisms affecting the adrenal glands, hypothalamus, pituitary gland, meninges or lungs through inappropriate antidiuretic hormone (ADH) secretion or by causing adrenal insufficiency. The pathophysiology of hyponatraemia with these conditions remains elusive. Recent research has demonstrated that inflammatory cytokines, such as interleukin (IL)-1 β and IL-6, are involved in the development of hyponatraemia. While syndrome of inappropriate ADH (SIADH) is a well-known complication of pulmonary inflammatory and infective diseases, the mechanism is poorly understood and has been attributed to hypoxia and decreased vascular volume. We report an unusual presentation of an elderly woman with euvolemic hyponatraemia, which on evaluation was found to be due to PTB causing SIADH. The patient was managed with anti-tuberculosis therapy, to which she responded well, with improvement in clinical parameters and increased sodium levels. This report highlights the occurrence of severe symptomatic hyponatraemia in tuberculosis. Due to the high prevalence and potential complications if left untreated, it is mandatory to consider tuberculosis in the differential diagnosis of hyponatraemia, particularly in elderly patients.