Unrelated bone marrow transplantation with a reduced toxicity myeloablative conditioning regimen in Wiskott-Aldrich syndrome

Genetic classification and confirmation of inherited platelet disorders: current status in Korea

Inherited platelet disorders (IPDs), which manifest as primary hemostasis defects, often underlie abnormal bleeding and a family history of thrombocytopenia, bone marrow failure, hematologic malignancies, undefined mucocutaneous bleeding disorder, or congenital bony defects. Wide heterogeneity in IPD types with regard to the presence or absence of thrombocytopenia, platelet dysfunction, bone marrow failure, and dysmegakaryopoiesis is observed in patients. The individual processes involved in platelet production and hemostasis are genetically controlled; to date, mutations of more than 50 genes involved in various platelet biogenesis steps have been implicated in IPDs. Representative IPDs resulting from defects in specific pathways, such as thrombopoietin/MPL signaling; transcriptional regulation; granule formation, trafficking, and secretion; proplatelet formation; cytoskeleton regulation; and transmembrane glycoprotein signaling are reviewed, and the underlying gene mutations are discussed based on the National Center for Biotechnology Information database and Online Mendelian Inheritance in Man accession number. Further, the status and prevalence of genetically confirmed IPDs in Korea are explored based on searches of the PubMed and KoreaMed databases. IPDs are congenital bleeding disorders that can be dangerous due to unexpected bleeding and require genetic counseling for family members and descendants. Therefore, the pediatrician should be suspicious and aware of IPDs and perform the appropriate tests if the patient has unexpected bleeding. However, all IPDs are extremely rare; thus, the domestic incidences of IPDs are unclear and their diagnosis is difficult. Diagnostic confirmation or differential diagnoses of IPDs are challenging, time-consuming, and expensive, and patients are frequently misdiagnosed. Comprehensive molecular characterization and classification of these disorders should enable accurate and precise diagnosis and facilitate improved patient management.

Successful Reduced Intensity Allogeneic Transplant With Full Donor Chimerism and Good Quality of Life in Adolescent Patient With Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked disease characterized by microthrombocytopenia, eczema, immune deficiency, and autoimmune phenomena. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment. Myeloablative conditioning is the most common regimen used for HSCT in patients with WAS to avoid the risk of mixed donor chimerism and autoimmunity post-HSCT. There is limited data on the use of reduced intensity conditioning for HSCT in patients with WAS. Here, we report a case with severe phenotype of WAS transplanted successfully with reduced intensity conditioning, which is an acceptable conditioning regimen and can be considered in patients with WAS with significantly impaired organ functions.

A novel large deletion and single nucleotide insertion in the Wiskott-Aldrich syndrome protein gene

Deletion mutations of WAS are relatively rare and the precise localization of large deletions in the genome has rarely been described in previous studies. We report here a 5-month-old boy with a large deletion mutation in WAS that completely abolished protein expression. To localize the deletion, a 2816-bp-length sequence that spans between exons 9 and 12 was amplified. PCR amplification of the patient's sample revealed a single band of about 1 kb in contrast to the 2816-bp-amplicon in the control. Genomic DNA sequencing of the patient revealed a 1595-bp-deletion and an adenine insertion (g.5247_6841del1595insA). This large deletion of WAS resulted in partial loss of exon 10 and intron 11, and a complete loss of intron 10 and exon 11.

Hematopoietic cell transplantation for Wiskott-Aldrich syndrome: advances in biology and future directions for treatment

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by a triad of diagnostic clinical elements: immunodeficiency, eczema, and hemorrhage caused by thrombocytopenia with small-sized platelets. The formal proof that hematopoietic cell transplantation (HCT) could be used to cure WAS revealed a requirement for both immunosuppression and myelosuppression that still underlies the standard approach to curative therapy today. The current short- and long-term toxicities of HCT are the main stumbling block for the ability to cure every patient with WAS and X-linked thrombocytopenia, and much remains to be done.

Evidence for long-term efficacy and safety of gene therapy for Wiskott-Aldrich syndrome in preclinical models

Wiskott-Aldrich Syndrome (WAS) is a life-threatening X-linked disease characterized by immunodeficiency, thrombocytopenia, autoimmunity, and malignancies. Gene therapy could represent a therapeutic option for patients lacking a suitable bone marrow (BM) donor. In this study, we analyzed the long-term outcome of WAS gene therapy mediated by a clinically compatible lentiviral vector (LV) in a large cohort of was(null) mice. We demonstrated stable and full donor engraftment and Wiskott-Aldrich Syndrome protein (WASP) expression in various hematopoietic lineages, up to 12 months after gene therapy. Importantly, we observed a selective advantage for T and B lymphocytes expressing transgenic WASP. T-cell receptor (TCR)-driven T-cell activation, as well as B-cell's ability to migrate in response to CXCL13, was fully restored. Safety was evaluated throughout the long-term follow-up of primary and secondary recipients of WAS gene therapy. WAS gene therapy did not affect the lifespan of treated animals. Both hematopoietic and nonhematopoietic tumors arose, but we excluded the association with gene therapy in all cases. Demonstration of long-term efficacy and safety of WAS gene therapy mediated by a clinically applicable LV is a key step toward the implementation of a gene therapy clinical trial for WAS.