Natural history and early diagnosis of LAD-1/variant syndrome |
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Authors: | Kuijpers Taco W van Bruggen Robin Kamerbeek Nanne Tool Anton T J Hicsonmez Gonul Gurgey Aytemiz Karow Axel Verhoeven Arthur J Seeger Karl Sanal Ozden Niemeyer Charlotte Roos Dirk |
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Institution: | Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands. t.w.kuijpers@amc.uva.nl |
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Abstract: | The syndrome of leukocyte adhesion deficiency (LAD) combined with a severe Glanzmann-type bleeding disorder has been recognized as a separate disease entity. The variability in clinical and cell biological terms has remained largely unclear. We present data on 9 cases from 7 unrelated families, with 3 patients being actively followed for more than 12 years. The disease entity, designated LAD-1/variant syndrome, presents early in life and consists of nonpussing infections from bacterial and fungal origin, as well as a severe bleeding tendency. This is compatible with 2 major blood cell types contributing to the clinical symptoms (ie, granulocytes and platelets). In granulocytes of the patients, we found adhesion and chemotaxis defects, as well as a defect in NADPH oxidase activity triggered by unopsonized zymosan. This last test can be used as a screening test for the syndrome. Many proteins and genes involved in adhesion and signaling, including small GTPases such as Rap1 and Rap2 as well as the major Rap activity-regulating molecules, were normally present. Moreover, Rap1 activation was intact in patients' blood cells. Defining the primary defect awaits genetic linkage analysis, which may be greatly helped by a more precise understanding and awareness of the disease combined with the early identification of affected patients. |
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