Evaluation of the FCGR2B polymorphism in children with immune thrombocytopenia.

Background: Childhood immune thrombocytopenia (ITP) is an immune-mediated disease characterized by an isolated low platelet count. Pathogenesis of ITP is complex but many patients have platelet specific autoantibodies leading to accelerated clearance of opsonized platelets by Fc-gamma receptor (FcγR) bearing phagocytes, particularly in the spleen. In humans, there are three main types of Fcγ receptors: high-affinity FcγRI and low-affinity FcγRII and FcγRIII. About FcγRII, genetic variation of FCGR2B is associated with response to IVIg treatment in patients with Kawasaki disease and ITP.

Methods: We used a TaqMAMA genotyping assay for detection of rs1050501 FCGR2B polymorphism in children with chronic ITP. A SNP rs1050501 (GenBank access number NG_023318.1, Homo sapiens Fc fragment of IgG receptor IIb [FCGR2B]) on chromosome 1 showing a T/C transition in position 15894 on FCGRB2 gene was chosen in this study. A series of experiments was conducted to evaluate the performance of the FCGR2B-MAMAPCR real time on a QuantStudio™ 5 Real-Time PCR System as compared to the 7500 Real-Time PCR System.

Results: Background noise, genotypes discrimination, variability, allele and genotype frequencies and concordance were obtained. About clinical validation, all 60 samples collected from chronic ITP patients were analyzed. We found 53 on the 60 patients (88.4%) were homozygotes (52 TT and 1 CC) and 7/60 (11.6%) heterozygotes (TC).

Conclusions: The ability of the FCGR2B-MAMAPCR real time to detect rs1050501 FCGR2B polymorphism in children with chronic ITP on the QuantStudio™ 5 System is comparable to that on the 7500 System.