Psychogenic polydipsia: A diagnostic challenge

Primary polydipsia (PP) is a disorder that is clinically characterised by excessive thirst accompanied by increased fluid intake and subsequent excessive excretion of urine without an obvious cause. PP in childhood due to psychogenic causes is a rare condition and may be more prevalent than thought. The differential diagnosis of polydipsia and polyuria is broad due to extensive associated disease spectrum, including renal, endocrine, and neurological diseases. Furthermore, differentiating PP from diabetes insipidus (DI) is essential because the treatment of the latter could be deleterious in patients with PP. We present the case of a 3-year-old boy who presented with psychogenic polydipsia. In the present case, the child was started on desmopressin, considering it a case of DI, in view of the history of increased water intake and urinary output. However, a detailed psychological assessment of the child revealed the case to be an autism spectrum disorder. Subsequently, desmopressin was discontinued, and there was a rapid normalisation of fluid intake along with significant reduction in the urine output after starting psychological intervention and implementing strict water restriction. This confirmed the diagnosis as a case of psychogenic polydipsia, which is a common occurrence in children with developmental disorders.