Wiskott-Aldrich Syndrome Presenting with JMML-Like Blood Picture and Normal Sized Platelets

Clinical Features and Outcomes of 23 Patients with Wiskott-Aldrich Syndrome: A Single-Center Experience

Objective

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immune deficiency characterized by microthrombocytopenia, eczema, and recurrent infections. We aimed to evaluate the clinical features and outcomes of a WAS cohort.

Materials and Methods

We retrospectively evaluated the clinical courses, immunological features, treatments, and outcomes in a total of 23 WAS patients together with data related to 11 transplanted cases among them between 1982 and 2019.

Results

Before admission, 11 patients (48%) were misdiagnosed with immune thrombocytopenia. WAS scores were mostly 4 or 5. Eleven patients were transplanted and they had an overall survival rate of 100% during a median follow-up period of 8.5 years (range: 8 months to 20 years). Five patients who were not transplanted died at a median of 7 years (range: 2-26 years). Nontransplanted patients had high morbidity due to organ damage, mostly caused by autoimmunity, bleeding, and infections. Two novel mutations were also defined.

Conclusion

All male babies with microthrombocytopenia should be evaluated for WAS. Hematopoietic stem cell transplantation should be performed at the earliest age with the best possible donors.

Somatic mutations activating Wiskott-Aldrich syndrome protein concomitant with RAS pathway mutations in juvenile myelomonocytic leukemia patients

The WAS gene product is expressed exclusively in the cytoplasm of hematopoietic cells and constitutional genetic abrogation of WASP leads to Wiskott-Aldrich syndrome (WAS). Moreover, mutational activation of WASP has been associated with X-linked neutropenia. Although studies reported that patients with constitutional WAS mutations affecting functional WASP expression may present juvenile myelomonocytic leukemia (JMML)-like features, confounding differential diagnosis above all in the copresence of mutated RAS, an activating somatic mutation of WASP has not been previously described in JMML patients. In our ongoing studies on JMML genomics, we at first detected a somatic WAS mutation in a major clone found at two consecutive relapses in one of two twins with JMML. Both twins were treated with hematopoietic stem cell transplantation after diagnosis of JMML. The somatic WAS mutation detected here displayed an activating WASP phenotype. Screening of 46 sporadic JMML patients at disease onset for mutations in the same PBD domain of WAS revealed two additional singleton patients carrying minor mutated clones. This is the first study to associate somatically acquired WASP mutations with a hematopoietic malignancy and increases insight in the complexity of the genomic landscape of JMML that shows low recurrent mutations concomitant with general hyperactivation of RAS pathway signaling.