الفهرس 
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Abstract
The Wiskott-Aldrich syndrome protein (WASp) is a multifaceted protein comprising 502 amino acids encoded by the WASp gene. The WASp gene mutation is connected to three distinct phenotypes: the classic WAS; the milder phenotype XLT; and congenital XLN with variable myelodysplasia.
Occasionally, WAS/XLT is misdiagnosed as ITP before other clinical features are fully developed, which can lead to inappropriate treatment and delays in life-saving definitive therapy.
Thus, the purpose of this study was to assess WASp expression on CD3+ T-cells by flow cytometry in terms of percentage of CD3+T cells with positive WASp and the median log (mean fluorescence intensity: MFI) of WASp in male infants and children diagnosed with chronic ITP and others with unexplained thrombocytopenia with or without eczema, recurrent infections.
Twenty-two male infants and children were enrolled in the study whose ages ranged between 2.5-14 years with mean (SD) of 8 (4)years. They were recruited from the Pediatric Hematology and Oncology Unit, and the Pediatric Allergy, Immunology and Rheumatology Unit, Children’s Hospital, Ain Shams University as follow: chronic ITP represented the main diagnosis in 19 patients (86%), two patients with WAS (one was probable and the other was genetically confirmed during the study) fulfilling a score of 3 and 4 respectively by the 5-point severity scoring system for WASp gene mutations related diseases) and the remaining patient had unexplained thrombocytopenia and positive family history of similar condition in his brother and maternal uncle and was genetically diagnosed with XLT.
The current study revealed that the MPV of the studied patients were within normal limits and was comparable to the healthy controls. Similarly, WASp expression on CD3+ T-cells of all studied patients was comparable to the healthy controls; Interestingly, the patient with probable WAS had defective WASp expression (45 %) 4 years ago, measured at the Clinical Immunology Laboratory, Department of Pediatric Immunology at Abu El Reesh Children’s Hospital, Cairo University. This might be related to the phenomenon of somatic reversion with partial improvement of the phenotype. There was a significant positive correlation between the percentage of CD3+ T-cells with positive WASp and the median log (MFI) of WASp expression.
There was no significant association between the absolute lymphocyte count and WASp expression among the studied patients. Of worth to note, that none of the patients had lymphopenia and among the studied patients, the 3 patients with WASp gene mutations (one was probable) and some chronic ITP patients had normal immunoglobulins levels except one patient with chronic ITP was found to have selective IgA deficiency and all had within normal lymphocytes subpopulations by flow cytometry
In conclusion, our study findings are in favor of the assessment of WASp expression on CD3+ T-cells, among other clinical clues including eczema, failure to thrive, autoimmunity, recurrent infection, and/or positive family history, to consider WAS/XLT in infants and children with persistent or chronic thrombocytopenia, and that normal WASp expression or MPV does not exclude the possibility of WAS/XLT in the presence of other suggestive clinical features to consider genetic diagnosis. We recommended further studies on wider scale to evaluate male pediatric patients with unexplained thrombocytopenia especially with positive family history and/or additional features of unusual allergy or infections for possible WAS/XLT.