Mumps Encephalitis in a Measles Rubella (MR)-Vaccinated Child: A Rare but Preventable Complication.

Mumps is a vaccine-preventable disease caused by the mumps virus, mainly affecting the salivary glands. It can cause serious complications, including mumps encephalitis. Despite widespread immunization practices, mumps outbreaks persist among both vaccinated and unvaccinated populations, raising issues of concern regarding herd immunity. Mumps encephalitis, although rare, can produce serious complications warranting prompt diagnosis and management. Here, in this case report, we present a five-year-old girl who presented with fever, bilateral parotid swelling, and a single episode of abnormal movement in the form of dystonia associated with fixed gaze and disorientation. The patient had received two doses of the measles rubella (MR) vaccine as per India's universal immunization program (UIP). Laboratory investigations showed high amylase levels, positive serum mumps IgM, and cerebrospinal fluid pleocytosis; all indicative of mumps encephalitis. Brain imaging was normal, excluding other neurological causes. Initial empirical antibiotics and acyclovir were discontinued following the diagnosis of mumps encephalitis. The patient showed improvement within 48 hours of supportive treatment. This case highlights the importance of considering mumps encephalitis in pediatric patients with mumps showing neurological symptoms. It also demonstrates the public health impact of omitting the mumps vaccine from India's UIP and the major role of the mumps, measles, and rubella (MMR) vaccination in preventing such complications.