Background: Bare lymphocyte syndrome type II (BLS II) is a rare form of severe combined immunodeficiency caused by mutations in the CIITA 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 CIITA 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.
Results: The patient presented with acute meningoencephalomyelitis confirmed by MRI findings and was later found to carry a homozygous pathogenic variant in the CIITA gene p.(Leu473Hisfs*15). The patient had no MCH II expression, confirming the genetic diagnosis of autosomal recessive BLS II. Surprisingly, the patient's prior clinical history was unremarkable for significant infections or autoimmunity.
Conclusions: We report a case with a novel CIITA gene mutation presenting atypically with a late and isolated severe infection. Isolated severe meningoencephalomyelitis may be a manifestation of primary immunodeficiency.
Keywords: CIITA gene; MHC II; genetic disorder; meningoencephalomyelitis; neurologic disease; novel mutation; type II bare lymphocyte syndrome.
© 2023 Alosaimi, Hamad, AlShammari, Jamjoom and Musibeeh.