Bare lymphocyte syndromes (BLS) refer to a group of rare genetic disorders that primarily affect the immune system. These conditions manifest when the body's lymphocytes, a type of white blood cell responsible for fighting infections, fail to mature properly. Synonyms for BLS can include "barely there lymphocyte syndromes", "deficient lymphocyte syndromes", and "lymphocyte maturation disorders". These terms highlight the underlying problem of inadequate lymphocyte development and emphasize the compromised immune function in individuals with BLS. Although BLS is a diverse set of disorders, they all share the common feature of impaired lymphocyte maturation, which can lead to recurrent infections, increased susceptibility to illnesses, and various complications.