Frequency of Fc gamma receptor IIIa-158V polymorphisms in Egyptian children with immune thrombocytopenic purpura

ABSTRACT

Immune thrombocytopenic purpura [ITP] is a bleeding disorder of infants, children and adults. The majority of affected children have the acute form of ITP, defined by duration of thrombocytopenia [<150 x 10[9]/L] of <6 months. Previous studies have shown that Fc gamma receptor [FcyRs] play crucial roles in platelet phagocytosis; antibodies bound to platelets have their Fc portion exposed which allows binding to monocytes/macrophages that express Fc receptors for lgG [FcgammaRs]. The Fc gammaRIIla Valine [V] has increased affinity for three separate lgG subclasses when compared with the FcgammaRIlIa Phenylalanine [F]. The aim of the present study was to assess the frequency of occurrence of the high affinity allelic variant FcgammaRllIa-158V in Egyptian children with ITP in comparison to normal individuals. Determination of FcgammaRlIIa genotype was performed for 30 ITP patients and 10 healthy control subjects by nested PCR followed by RFLP analysis. In our study, the allelic frequency of FcgammaRIlIa-158V was [76.6%] among ITP patient group in contrast to [20%] among the control group. These results suggest that FcgammaRllIa-158 V/F polymorphism contributes to the pathogenesis of childhood ITP by increased clearance of antibodysensitized platelets by the high affinity FcgammaRlIIa-158V allelic variant. Besides the epidemiologic and pathophysiologic interest, this knowl edge may be of use in the future designing of novel therapeutic interventions: