Wiskott-Aldrich syndrome

Organ-based clues for diagnosis of inborn errors of immunity: A practical guide for clinicians

Inborn errors of immunity (IEI) comprise a group of about 490 genetic disorders that lead to aberrant functioning or the development of distinct immune system components. So far, a broad spectrum of IEI-related manifestations has been noted in the literature. Due to overlapping signs and symptoms of IEI, physicians face challenges in appropriately diagnosing and managing affected individuals. The last decade has witnesses improving in the molecular diagnosis of IEI patients. As a result, it can be the mainstay of diagnostic algorithms, prognosis, and possibly therapeutic interventions in patients with IEI. Furthermore, reviewing IEI clinical complications demonstrates that the manifestations and severity of the symptoms depend on the involved gene that causes the disease and its penetrance. Although several diagnostic criteria have been used for IEI, not every patient can be explored in the same way. As a result of the failure to consider IEI diagnosis and the variety of diagnostic capabilities and laboratory facilities in different regions, undiagnosed patients are increasing. On the other hand, early diagnosis is an almost essential element in improving the quality of life in IEI patients. Since there is no appropriate guideline for IEI diagnosis in different organs, focusing on the clues in the patient's chief complaint and physical exams can help physicians narrow their differential diagnosis. This article aims to provide a practical guide for IEI diagnosis based on the involved organ. We hope to assist clinicians in keeping IEI diagnosis in mind and minimizing possible related complications due to delayed diagnosis.

Allogeneic hemopoietic stem cell transplantation (HSCT) for Wiskott-Aldrich syndrome: a report of the Spanish Working Party for Blood and Marrow Transplantation in Children (GETMON)

Allogeneic stem cell transplantation is the only curative treatment for Wiskott-Aldrich syndrome. The authors retrospectively analyzed the outcome with this procedure in 13 patients with severe Wiskott-Aldrich syndrome transplanted in 5 Spanish centers from 1989 to 2006. A patient was transplanted twice from the same donor due to a late engraftment failure. Age at transplant ranged from 7 to 192 months (median 30 months). There were 10 matched donors (3 related and 7 unrelated), 2 mismatched unrelated, and 1 haploidentical. Conditioning regimen consisted of busulfan and cyclophosphamide (BuCy) in 11 cases and fludarabine and melfalan (1) or BuCy (1). ATG was added in transplants from non-genetically matched donors. GvHD prophylaxis consisted of cyclosporine and methotrexate in most patients plus T-cell depletion in the haploidentical HSCT. Nine of the 13 transplanted patients are alive with complete clinical, immunologic, and hematologic recovery 8-204 months (median 101 months) after HSCT. Eight surviving patients had been transplanted from matched donors (3 related and 5 unrelated) and 1 from a haploidentical donor. Four patients died, 2 transplanted from matched donors (1 from acute GvHD and organ failure, 1 from a lymphoproliferative disorder after a second transplant), and 2 transplanted from mismatched unrelated donors (1 from acute GvHD and organ failure, 1 from graft failure and infection). Allogeneic hemopoietic stem cell transplantation must be utilized in all patients with severe Wisckott-Aldrich syndrome, using the most suitable graft variant for each patient.

Requirement for a complex of Wiskott-Aldrich syndrome protein (WASP) with WASP interacting protein in podosome formation in macrophages

Chemotactic migration of macrophages is critical for the recruitment of leukocytes to inflamed tissues. Macrophages use a specialized adhesive structure called a podosome to migrate. Podosome formation requires the Wiskott-Aldrich syndrome protein (WASP), which is a product of the gene defective in an X-linked inherited immunodeficiency disorder, the Wiskott-Aldrich syndrome. Macrophages from WASP-deficient Wiskott-Aldrich syndrome patients lack podosomes, resulting in defective chemotactic migration. However, the molecular basis for podosome formation is not fully understood. I have shown that the WASP interacting protein (WIP), a binding partner of WASP, plays an important role in podosome formation in macrophages. I showed that WASP bound WIP to form a complex at podosomes and that the knockdown of WIP impairs podosome formation. When WASP binding to WIP was blocked, podosome formation was also impaired. When WASP expression was reduced by small interfering RNA transfection, the amount of the complex of WASP with WIP decreased, resulting in reduced podosome formation. Podosomes were restored by reconstitution of the WASP-WIP complex in WASP knockdown cells. These results indicate that the WASP-WIP complex is required for podosome formation in macrophages. When podosome formation was reduced by blocking WASP binding to WIP, transendothelial migration of macrophages, the most crucial process in macrophage trafficking, was impaired. These results suggest that a complex of WASP with WIP plays a critical role in podosome formation, thereby mediating efficient transendothelial migration of macrophages.

Combined Immune Deficiencies in Children

Combined immune deficiencies are a heterogeneous group of congenital disorders usually attributable to a single gene defect. The hallmark of these disorders is recurrent infections resulting from defects in both T- and B-cell function. This article reviews the basic components of the immune system as well as the clinical presentation, laboratory findings, and treatment for 3 distinct combined immune deficiencies.

Successful unmanipulated haploidentical bone marrow transplantation from an HLA 2-locus-mismatched mother for Wiskott-Aldrich syndrome after unrelated cord blood stem cell transplantation

The authors describe a boy with Wiskott-Aldrich syndrome (WAS) who was diagnosed immediately after birth using flow cytometric and genetic analysis. At 1 year of age he received unrelated cord blood stem cell transplantation (UCBSCT); however, the sex chromosomes of the peripheral blood mononuclear cells showed that the recipient type was over 70%. This rate gradually increased to over 90% after immunosuppressant therapy was discontinued. Clinical manifestations, including high fever, graft-versus-host disease (GVHD)-like eruptions, and signs of infection recurred. Results of flow cytometric and genetic analysis of mononuclear cells from the boy's mother were normal with no mutation. Three months after UCBSCT, he received an unmanipulated HLA-haploidentical 2-locus-mismatched bone marrow transplant (BMT) from his mother. The prophylaxis against GVHD was tacrolimus and short-term methotrexate. Hematopoietic reconstitution was rapid and fluorescence in situ hybridization analysis revealed sustained engraftment. Grade II acute GVHD developed but improved rapidly with the administration of methylprednisolone. The patient is progressing well and displays complete chimerism 2 years after the BMT. This case suggests that unmanipulated haploidentical BMT from the mother might be feasible not only for malignant disease but also for immunodeficiency disease patients who urgently need stem cell transplants and have no HLA-identical donors.

Mutations of the Wiskott-Aldrich Syndrome Protein (WASP): hotspots, effect on transcription, and translation and phenotype/genotype correlation

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive immune deficiency disorder characterized by thrombocytopenia, small platelet size, eczema, recurrent infections, and increased risk of autoimmune disorders and malignancies. X-linked thrombocytopenia (XLT) is an allelic variant of WAS which presents with a milder phenotype, generally limited to thrombocytopenia. WAS and XLT are caused by mutations of the Wiskott-Aldrich syndrome protein (WASP) gene which encodes a 502-amino acid protein, named WASP. WASP is thought to play a role in actin cytoskeleton organization and cell signaling. Here, we report the identification of 141 unique mutations, 71 not previously reported, from 227 WAS/XLT families with a total of 262 affected members. When possible we studied the effects of these mutations on transcription, RNA splicing, and protein expression. By analyzing a large number of patients with WAS/XLT at the molecular level we identified 5 mutational hotspots in the WASP gene and have been able to establish a strong association between genotype and phenotype.

Clinical course of patients with WASP gene mutations

Mutations of the Wiskott-Aldrich syndrome protein (WASP) gene result either in the classic Wiskott-Aldrich syndrome (WAS) or in a less severe form, X-linked thrombocytopenia (XLT). A phenotype-genotype correlation has been reported by some but not by other investigators. In this study, we characterized WASP gene mutations in 50 Japanese patients and analyzed the clinical phenotype and course of each. All patients with missense mutations were WASP-positive. In contrast, patients with nonsense mutations, large deletions, small deletions, and small insertions were WASP-negative. Patients with splice anomalies were either WASP-positive or WASP-negative. The clinical phenotype of each patient was correlated with the presence or absence of WASP. Lack of WASP expression was associated with susceptibility to bacterial, viral, fungal, and Pneumocystis carinii infections and with severe eczema, intestinal hemorrhage, death from intracranial bleeding, and malignancies. Rates for overall survival and survival without intracranial hemorrhage or other serious complications were significantly lower in WASP-negative patients. This analysis provides evidence for a strong phenotype-genotype correlation and demonstrates that WAS protein expression is a useful tool for predicting long-term prognosis for patients with WAS/XLT. Based on data presented here, hematopoietic stem cell transplantation should be considered, especially for WASP-negative patients, while the patients are young to improve prognosis.