X-Linked Agammaglobulinemia With Chronic Meningoencephalitis: A Diagnostic Challenge.

X-linked agammaglobulinemia (XLA) is a primary disorder of humoral immunity characterized by Bruton tyrosine kinase gene mutations resulting in a primary antibody deficiency. While an intact T-cell function largely protects against majority of viral infections, enteroviruses are notorious for infecting these patients due to impaired mucosal immunity. Although the incidence of enteroviral meningoencephalitis in XLA is only 1-5%, yet the mortality is quite high. A typical presentation of enteroviral encephalitis in XLA is a subacute to chronic nervous system infection. A progressive loss of motor and cognitive milestones, spastic quadriplegia, coma, and death are common presentations. The histopathological features reflect gliosis, gradual neuronal loss, neuronophagia, and microglial proliferation. We describe the clinical and brain histopathological findings in a 2-year-old boy with XLA and progressive encephalitis, possibly due to an enteroviral infection.