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

Area of Science:

• Immunology
• Genetics
• Pediatrics

Background:

• Major histocompatibility complex (MHC) class II deficiency is a rare primary immunodeficiency disorder (PID).
• Fewer than 200 cases are documented globally.
• It affects the adaptive immune system's ability to present antigens.

Observation:

• An 8-month-old girl presented with recurrent pneumonia, prolonged fever, and antibiotic resistance.
• She exhibited low serum immunoglobulin levels, but normal counts for NK, B, and T cells.
• Flow cytometry revealed negative HLA-DR proteins on peripheral blood mononuclear cells (PBMCs).

Findings:

• Whole exome sequencing (WES) identified a novel homozygous mutation in the RFXANK gene (NM_001278728: exon 5: c.495G>A: p.Trp165*).
• The patient was diagnosed with MHC class II deficiency despite having normal CD4+ T cell counts.
• Intra-venous immune-globulin (IVIG) replacement and broad-spectrum antibiotics were initiated.

Implications:

• This case highlights that MHC class II deficiency should be considered in consanguineous families, even with normal CD4+ T cell counts.
• WES is an effective diagnostic tool for this rare PID.
• Hematopoietic stem cell transplantation (HSCT) can be a life-saving treatment.