Adaptive immune defects in a patient with leukocyte adhesion deficiency type III with a novel mutation in FERMT3

To the Editor,
Leukocyte adhesion deficiency (LAD) is a rare primary immunodeficiency disease characterized by impairment of phagocyte adhesion. Three subtypes have been classified by distinct phases of the adhesion cascade. LAD-III is caused by defects in signaling pathways used for integrin activation in all hematopoietic cell types leading to recurrent infections with poor platelet aggregation resembling Glanzmann’s thrombasthenia. Mutations in FERMT3 have been identified to underlie LAD-III. FERMT3 encodes kindlin-3, one of the focal adhesion proteins which contain a FERM domain located at the carboxyl terminus binding to b-integrin cytoplasmic tails. This molecule cooperates with the cytoskeletal protein talin leading to integrin activation. It also stabilizes active conformations of the integrin subunits and the ligand binding. Evidently, integrins are widely expressed in many cell types including T and B lymphocytes. Defects in integrin function therefore could lead to both innate and adaptive immune dysfunctions. However, almost all reported cases of LAD-III only had innate immune defects. Here, we describe a female Thai patient who was diagnosed with LAD-III, yet presenting with a mild atypical phenotype in which a humoral immune defect was detected.