MHC class I deficiency (MHC1D) is a rare recessive genetic immune disorder endorsed by a partial or complete absence of major histocompatibility complex (MHC) or human leukocyte antigen (HLA) expression. BLS could be grouped as Type I, Type II and Type III based on defective surface MHC expression. The mutations in the TAP subunits are one of the most common features of BLS type I. MHC I deficiency due to tapasin (TAPBP) deficiency was also discovered recently.
