bare lymphocyte syndrome
A primary immunodeficiency characterized by absent or deficient MHC class I or II molecule expression on immune cells.
Full Definition
Bare lymphocyte syndrome (BLS) encompasses a group of primary immunodeficiencies caused by defects in major histocompatibility complex (MHC) molecule expression. Type I BLS involves absent MHC class I molecules, while Type II BLS involves absent MHC class II molecules. These defects impair antigen presentation to T cells, resulting in severe combined immunodeficiency presentations with recurrent infections, failure to thrive, and poor vaccine responses. Type II BLS is more common and often presents with chronic diarrhea and respiratory infections.
Usage
Usage note: Specify Type I or Type II when the specific form is known; BLS acceptable as abbreviation.
In Context
- "Flow cytometry revealed absent HLA-DR expression, confirming Type II bare lymphocyte syndrome." — Laboratory diagnosis
- "Bare lymphocyte syndrome should be considered in patients with SCID-like presentations and normal lymphocyte counts." — Differential diagnosis