Novel Inherited N-terminus TAP1 Variants and Severe Clinical Manifestations- Are Genotype-Phenotype Correlations Emerging?

Major histocompatibility complex class I deficiency results from deleterious biallelic variants in TAP1, TAP2, TAPBP, and B2M genes. Only a few patients with variant-curated TAP1 deficiency (TAP1D) have been reported in the literature and the clinical phenotype has been variable with an emphasis on autoimmune and inflammatory complications. We report TAP1D in a Nepalese girl with a severe clinical phenotype with serious viral infections at a very young age. A novel frameshift termination variant near the protein's amino (N-) terminal was found. Variants in exon 1 of the TAP1 gene (as in our case) have not been reported previously. We also perform a brief review of TAP1D that hints at potential genotype-phenotype correlations. However, these findings need to be interpreted with due prudence given the small number of patients with TAP1D reported thus far.