Adult-onset neurodegeneration in XMEN diseasee

Background: XMEN (X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV), and N-linked glycosylation defect) disease results from loss-of-function mutations in MAGT1, a protein that serves as a magnesium transporter and a subunit of the oligosaccharyltransferase (OST) complex. MAGT1 deficiency dis-rupts N-linked glycosylation, a critical regulator of immune function. XMEN results in recurrent EBV infections and a propensity for EBV-driven malignancies. Although XMEN is recognized as a systemic congenital disorder of glycosylation (CDG), its neurological involvement is rare and poorly characterized. Cases: Two young men, ages 32 and 33, are described here with truncating mutations in MAGT1, progressive behavioral changes, and neurodegenerative symptoms. These features manifested well into adulthood. Both patients still presented with many of the molecular and clinical hallmarks of the typical XMEN patient, including chronic EBV viremia and decreased expression of NKG2D. Conclusion: While previously unrecognized, XMEN may include prominent and disabling CNS manifestations. How MAGT1 deficiency directly or indirectly contributes to neurodegeneration remains unclear. Elucidating this mechanism may contribute to the understanding of neurodegeneration more broadly.