TAP deficiency syndrome

Bare lymphocyte syndrome (BLS) is characterized by a severe down-regulation of HLA class I and/or class II molecules. In type 1 BLS the defect is confined to HLA class I molecules, while in type 2 BLS HLA class II molecules are down-regulated 1. Characterization of 22 patients with type 1 BLS over the last 22 years has revealed the existence of several clinically and immunologically distinct disease subsets 1–20. In this review we will focus on a recently characterized group of patients with a distinct disease phenotype due to a defective TAP complex, the peptide transporter complex associated with antigen presentation 2–15. We will describe clinical manifestations and immunological findings of patients suffering from TAP deficiency syndrome, and discuss the differential diagnosis and therapeutic options.