Case report: A late and isolated presentation of meningoencephalomyelitis uncovers a novel pathogenic variant in the gene.

Background: Bare lymphocyte syndrome type II (BLS II) is a rare form of severe combined immunodeficiency caused by mutations in the gene, which regulates major histocompatibility complex class II (MHC II) expression.

Objective: We report the case of a Saudi boy with a novel mutation in the gene who presented with acute and late meningoencephalomyelitis, resulting in severe neurodevelopmental regression.

Methods: We reviewed the patient's clinical and laboratory data obtained from medical records and performed a literature search on BLS II.