MHC Class II Deficiency with Normal CD4+ T Cell Counts: A Case Report.

Major histocompatibility complex (MHC) class II deficiency is a rare primary immunodeficiency disorder (PID) with less than 200 cases worldwide. Here, we report an 8 month-old girl with MHC class II deficiency with a novel homozygous mutation in RFXANK gene (NM_001278728: exon 5: c.495G>A: p.Trp165*) and normal CD4+ T cell counts, diagnosed by whole exome sequencing (WES) and negative HLA-DR proteins on peripheral blood mononuclear cell (PBMC) in flow cytometry. She was referred with pneumonia, prolonged fever, resistance to antibiotics (ceftriaxone, clindamycin, and vancomycin), and low serum immunoglobulin (IG) levels, while natural killer (NK), B, and T cells were normal. She received intra-venous immune-globulin (IVIG) replacement, broad spectrum antibiotics, and anti-fungal treatments. The presented case report is interesting not only because of the rarity of the PID but also due to normal CD4+ T cell counts. According to our experience, we suggest that physicians consider MHC class II deficiency in families with consanguineous marriages, even with normal CD4+ T cell counts. At the first, the diagnosis of the disease could be successfully perform using WES, and finally, treatment with hematopoietic stem cell transplantation can save the patients' lives.