A novel mutation in TAP1 gene leading to MHC class I deficiency: Report of two cases and review of the literature

- Two siblings presented with recurrent respiratory infections and bronchiectasia.
- They did not experience skin abscesses, but one had chronic hepatitis B infection.
- Genetic analysis revealed a novel frameshift mutation in exon 10 of the TAP1 gene.

Major histocompatibility complex (MHC) class I deficiency syndrome is a rare primary immunodeficiency caused by mutations in the peptide transporter complex associated with antigen presentation (TAP) gene which plays a crucial role in intracellular peptide antigen presentation. A few cases have been reported to date. Recurrent sinopulmonary infections and skin ulcers are the main characteristics of the syndrome. Here we report two siblings diagnosed with TAP1 deficiency syndrome associated only with recurrent sinopulmonary infections with the description of a novel mutation leading to a premature stop codon in TAP1 gene and review of the relevant literature. Both of the siblings had recurrent sinopulmonary infections since childhood, responded to antibiotherapy well, neither of them had hospitalization history because of infections. One had chronic hepatitis B infection which may possibly be related to TAP1 gene defect.