SIADH (Syndrome of Inappropriate ADH Secretion): Perplexing Look of Dengue Fever

Dengue is a mosquito-borne disease (female mosquitoes of the Aedes genus, principally Aedes aegypti) caused by any one of four closely related dengue viruses. It is endemic in tropical and subtropical continent. World health organization (WHO) currently estimates there may be 50 -100 million dengue infections worldwide every year with over 2.5 billion people at risk of dengue. Symptomatic dengue virus infection may manifests as undifferentiated fever, classical dengue fever (with or without unusual hemorrhages), and dengue hemorrhagic fever (with or without shock). Isolated organopathy or expanded dengue syndrome (EDS) was coined by WHO in the year 2012 to describe cases, which do not fall into either dengue shock syndrome or dengue hemorrhagic fever. The atypical manifestations noted in expanded dengue are multisystemic and multifaceted with organ involvement, such as liver, brain, heart, kidney, central/peripheral nervous system, gastrointestinal tract, lympho reticular system. Dengue virus has long been considered as a non-neurotropic virus, as animal studies have shown that virus does not cross blood brain barrier. Hyponatremia may be found in association with dengue fever and is thought to be caused by peripheral fluid extravasation and resulting intravascular hypovolaemia. But hyponatremia due to syndrome of inappropriate secretion of anti-diuretic hormone (SIADH) in Dengue fever is rare. We report a 40 years old male who was diagnosed as Dengue fever (Dengue Ns1Ag positive) with thrombocytopenia and hyponatremia. He was admitted and further investigations revealed SIADH. He responded well to cautious sodium replacement and addition of tolvaptan. He recovered completely and was discharged after one week. Thus, all clinicians should keep in mind the possibility of SIADH as a part of expanded dengue syndrome.