Síndrome de Wiskott-Aldrich en España: incidencia, mortalidad y sesgo de género durante 21 años / 21 years of Wiskott-Aldrich syndrome in Spain: incidence, mortality, and gender bias

Introducción El síndrome de Wiskott-Aldrich (SWA) es un trastorno raro ligado al cromosoma X que afecta predominantemente a los hombres. Objetivo Este estudio tiene como objetivo investigar la incidencia y muerte intrahospitalaria asociada al SWA en España, así como su sesgo de género. Métodos Se realizó un estudio epidemiológico retrospectivo de base poblacional de 97 pacientes con SWA diagnosticados en hospitales españoles entre 1997 y 2017, a través del Sistema Nacional del Conjunto Mínimo Básico de Datos al alta hospitalaria. Resultados Nuestros resultados revelaron que la incidencia media anual de SWA en España fue de 1,1 por 10 000 000 habitantes (IC95% 0,45−2,33). El riesgo relativo fue mayor en hombres que en mujeres (2,42). El diagnóstico de SWA se produce a edades más tardías en las mujeres (mediana de edad de 47 años) en comparación con los hombres (mediana de edad de 5,5 años). Solo hombres ingresaron al hospital al menos en 10 ocasiones diferentes y todas las muertes se detectaron en hombres. La tasa de mortalidad intrahospitalaria fue del 9,28% en WAS, siendo la mayoría de las muertes asociadas a hemorragia cerebral o infección. Conclusiones El SWA, una enfermedad rara, se diagnosticó en edades más tardías en mujeres y la mortalidad, mayoritariamente asociada a hemorragia cerebral e infección, afectó a hombres (AU)

Background Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder considered to predominantly affect males. Objective This study aims to investigate the incidence and intrahospital death associated with WAS in Spain as well as the gender bias. Methods A population-based retrospective epidemiological study of 97 WAS patients that were diagnosed in Spanish hospitals between 1997 and 2017 was conducted by using data from the National Surveillance System for Hospital Data. Results Our results revealed that the mean annual incidence of WAS in Spain was 1.1 per 10,000,000 inhabitants (CI95% 0,45-2,33). The relative risk was higher in male than female (2.42). WAS diagnosis occurs at later ages in women (median age of 47 years) compared to men (median age of 5.5 years). Only male were admitted to the hospital at least in 10 different occasions and all deaths were detected in men. The intra-hospital death rate was of 9.28% inWAS, being most of the deaths associated with brain hemorrhage or infection. Conclusions WAS, a rare disease, is diagnoses at later ages in women and the mortality wasfound in males mostly associated with brain hemorrhage and infection (AU)

Wiskott Aldrich syndrome: healthcare utilizations and disparities in transplant care.

Wiskott Aldrich syndrome (WAS) is a rare disease and hematopoietic stem cell transplant (HCT) is considered the treatment modality of choice for WAS. We conducted a cross-sectional analysis on the KIDS' pediatric inpatient database and compared hospitalization rates, complications and healthcare utilizations in the transplant and non-transplant arms. Of the 383 pediatric admissions with diagnosis of WAS between 2006-2012, 114 underwent transplant and 269 did not. The non-transplant arm included older children, female patients and more African Americans. Death rates, income and payer source were similar in both arms, however the total charge for each admission was higher in the transplant arm. Emergency room visits were similar but non-elective admissions were more in the non-transplant arm. Length of stay was prolonged in the transplant arm. When comparing morbidities, lymphomas, ulcerative colitis and autoimmune complications of WAS were seen only in the non-transplant arm. Our study shows that transplant is the largest contributor to healthcare utilization in WAS patients. We identified healthcare disparities based on race and socioeconomic status and found that this rare disease is being appropriately directed to centers with HCT expertise. We noted a change in practice moving away from splenectomy in WAS patients.

Outcomes after Allogeneic Transplant in Patients with Wiskott-Aldrich Syndrome.

Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder characterized by a triad of immunodeficiency, eczema, and thrombocytopenia. Currently, hematopoietic stem cell transplantation (HSCT) is the most reliable curative treatment with excellent results for patients with HLA-matched family or unrelated donors. However, even after fully myeloablative preparative regimens, mixed donor chimerism is a potential concern. We performed a retrospective chart review of 12 children who underwent allogeneic HSCT for WAS to report our experience. The median age at transplant was 10.5 months (range, 3 to 39). The median nucleated cell dose from the marrow was 4.55 × 109/kg (range, .3 to 7.9). The median times to neutrophil and platelet engraftment were 19 days (range, 13 to 27) and 18.5 days (range, 12 to 31), respectively. The rate of overall survival was 92% with median follow-up of 67 months (range, 3 to 146). Two patients developed grade IV acute graft-versus-host disease, and 1 died on day +99. Five of 12 patient's (42%) had mixed donor chimerism (range, 12% to 85%) at day +180. None of the pretransplant patient parameters was predictive of mixed chimerism. Nonetheless, of these 5 patients, 2 had normalization of the platelet count despite the mixed chimerism, 2 had full donor chimerism after receiving a second transplant with the same donor, and 1 remains transfusion dependent awaiting a second transplant. Hence, even with a significant rate of mixed chimerism, HSCT provides substantial benefit to WAS patients, with excellent overall survival.

A risk factor analysis of outcomes after unrelated cord blood transplantation for children with Wiskott-Aldrich syndrome.

Wiskott-Aldrich syndrome is a severe X-linked recessive immune deficiency disorder. A scoring system of Wiskott-Aldrich syndrome severity (0.5-5) distinguishes two phenotypes: X-linked thrombocytopenia and classic Wiskott-Aldrich syndrome. Hematopoietic cell transplantation is curative for Wiskott-Aldrich syndrome; however, the use of unrelated umbilical cord blood transplantation has seldom been described. We analyzed umbilical cord blood transplantation outcomes for 90 patients. The median age at umbilical cord blood transplantation was 1.5 years. Patients were classified according to clinical scores [2 (23%), 3 (30%), 4 (23%) and 5 (19%)]. Most patients underwent HLA-mismatched umbilical cord blood transplantation and myeloablative conditioning with anti-thymocyte globulin. The cumulative incidence of neutrophil recovery at day 60 was 89% and that of grade II-IV acute graft-versus-host disease at day 100 was 38%. The use of methotrexate for graft-versus-host disease prophylaxis delayed engraftment (P=0.02), but decreased acute graft-versus-host disease (P=0.03). At 5 years, overall survival and event-free survival rates were 75% and 70%, respectively. The estimated 5-year event-free survival rates were 83%, 73% and 55% for patients with a clinical score of 2, 4-5 and 3, respectively. In multivariate analysis, age <2 years at the time of the umbilical cord blood transplant and a clinical phenotype of X-linked thrombocytopenia were associated with improved event-free survival. Overall survival tended to be better in patients transplanted after 2007 (P=0.09). In conclusion, umbilical cord blood transplantation is a good alternative option for young children with Wiskott-Aldrich syndrome lacking an HLA identical stem cell donor.

Stem cell transplantation for primary immunodeficiency diseases: the North American experience.

PURPOSE OF REVIEW: This review describes recent studies on outcomes after allogeneic hematopoietic cell transplantation for primary immunodeficiency in North America, including severe combined immunodeficiency (SCID), Wiskott-Aldrich syndrome and chronic granulomatous disease. RECENT FINDINGS: Using uniform diagnostic criteria, the Primary Immune Deficiency Treatment Consortium described the baseline characteristics of newly diagnosed infants with SCID in North America. Analysis of outcomes of hematopoietic cell transplantation for SCID in North America from 2000 to 2009 showed that young infants, and older infants without active infection, had excellent survival irrespective of type of donor or transplant approach with regard to conditioning. Although pretransplant conditioning with chemotherapy had a clear and strong negative impact on survival in infants with active infection at the time of transplant, among survivors, conditioning was associated with improved immune reconstitution. However, the potential late effects of conditioning in these infants remain to be characterized. Advances in transplant outcomes for Wiskott-Aldrich syndrome and chronic granulomatous disease support the strategy of early transplantation before the onset of severe complications; additional multicenter studies are needed to fully define optimal approaches. SUMMARY: The formation of the Primary Immune Deficiency Treatment Consortium, a multiinstitutional North American consortium, has contributed to our understanding of outcomes after transplant for primary immunodeficiency.

Impact of conditioning on outcome of hematopoietic stem cell transplantation for wiskott-Aldrich syndrome.

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for Wiskott-Aldrich syndrome (WAS). The aim of this retrospective study is to report the effect of the conditioning regimen and donor source on disease-free survival (DFS) in children undergoing HSCT for WAS. Fourteen children who underwent HSCT at 4 Israeli centers from 1996 to 2011 were included in this study. Five children were transplanted from matched related donors (4/5 siblings, 1/5 fully matched uncle) and other donors were used in 9 children. Six patients were conditioned with full dose busulfan/cyclophosphamide (Bu/Cy) whereas 8 patients were conditioned with other regimens. Thirteen of 14 patients (92.8%) are alive with a median follow-up of 3.4 years (range, 5 mo to 12.5 y). Nine patients (64.3%) survive with complete clinical, immunologic, and hematologic recovery. Children conditioned with full dose Bu/Cy had a 100% DFS, compared with children conditioned with other regimens, 25%±19% (P=0.022). Donor source was not associated with DFS. Graft failure was related to the use of conditioning regimens other than full dose Bu/Cy and not to the donor source. Further studies are required to determine the best conditioning regimen and optimal donor source for children with WAS.

Risk factor analysis of bloodstream infection in pediatric patients after hematopoietic stem cell transplantation.

Bloodstream infection (BSI) is a recognized cause of morbidity and mortality in children after hematopoietic stem cell transplantation (HSCT). However, there are limited reports on BSI after HSCT in pediatric patients in multiple centers. This study was a retrospective cohort analysis of consecutive patients who underwent allogeneic and autologous HSCT at the Department of Paediatrics, Hokkaido University Hospital, between 1988 and 2009; the Department of Paediatrics, Sapporo Hokuyu Hospital, between 2007 and 2009; and the Department of Paediatrics, Asahikawa Medical University, between 1989 and 2009. A total of 277 patients underwent HSCT during the study period. In this multicenter analysis, cases of BSI after HSCT were recorded in the early posttransplant period (within the first 100 d), and BSI was observed in 24 of 277 HSCT patients. Multivariate analysis showed that nonmalignant disease was an independent factor associated with BSI after HSCT (hazard ratio 6.3 for aplastic anemia or Wiskott-Aldrich syndrome patients; confidence interval, 1.4-12.8; P = 0.012). We conclude that aplastic anemia and Wiskott-Aldrich syndrome were the novel risk factors for BSI in pediatric patients after HSCT.

Outcomes of hematopoietic stem cell transplantation in primary immunodeficiency: a report from the Australian and New Zealand Children's Haematology Oncology Group and the Australasian Bone Marrow Transplant Recipient Registry.

We performed a retrospective analysis on the outcomes of 135 hematopoietic stem cell transplantations (HSCTs) for primary immunodeficiency disorders in Australian and New Zealand Children's Haematology Oncology Group transplantation centers between 1992 and 2008. The most common indications for HSCT were severe combined immunodeficiency, Wiskott-Aldrich syndrome, and chronic granulomatous disease. Five-year overall survival (OS) was 72% for the entire cohort. Disease-specific 5-year OS was 70% for severe combined immunodeficiency, 81% for Wiskott-Aldrich syndrome, and 69% for chronic granulomatous disease. Transplantation-related mortality (TRM) was 10% at day +100. TRM and OS were equivalent in recipients of related and unrelated donor transplants. Source of stem cells had no impact on TRM or OS with outcomes following unrelated umbilical cord blood similar to unrelated bone marrow. The presence of interstitial pneumonitis, active cytomegalovirus infection, or veno-occlusive disease were all independent variables that significantly decreased OS. This large series supports the use of HSCT as curative therapy for a range of primary immunodeficiency disorders, demonstrating excellent survival after both related and unrelated donor transplantation.

IBD and IBD mimicking enterocolitis in children younger than 2 years of age.

Inflammatory bowel disease (IBD) is uncommon in children younger than 2 years of age. The criteria for differentiating IBD from other diseases with similar clinical presentation is unclear. We describe 16 patients who, between 1984 and 2004, received a histological diagnosis of IBD during the first two years of life. Six patients presented with histological Crohn's disease, eight with ulcerative colitis and two with indeterminate colitis. The median age at diagnosis was 125 days (range 1 day to 18 months) and the medium follow up was 89 months (range 65 days to 20 years). The disease appeared to be very severe: four children (25%) underwent total parenteral nutrition (TPN), two received colectomy (12.5%) and three patients died. Many of the patients required an aggressive, multidrug, immunosuppressive approach (azathioprine [AZA], Infliximab, thalidomide, cyclosporine A). One child presented with a hypogammaglobulinaemia without any specific immunodeficiency, while in the other patients, Wiskott-Aldrich syndrome (WAS) (4 cases) and chronic granulomatous disease (CGD) (2 cases) were identified. In 6/16 cases, allergic colitis was first considered; these cases initially underwent cow's milk protein-free diet as the only therapy before IBD was finally diagnosed. In conclusion, early IBD has a severe prognosis and often needs an aggressive therapeutic approach. Furthermore, an improper diagnosis of allergic colitis might cause an important diagnostic delay. Some severe immunodeficiencies, such as WAS and CGD, may represent a problem in terms of differential diagnosis and might be wrongly diagnosed as very early onset IBD.

Results and long-term outcome in 39 patients with Wiskott-Aldrich syndrome transplanted from HLA-matched and -mismatched donors.

In this report, we present an analysis in 39 WAS patients treated by hematopoietic stem cell transplantation (HSCT) in our center since 1983. Fifteen patients received transplants from HLA-identical unrelated donors, 15 from nonidentical parental donors, and 9 from matched siblings. The overall survival rate is 90% in patients with matched donors and 50% in patients after nonidentical transplantation, with a mean follow-up time of 11 years. Treatment failures in the latter group were mainly related to graft rejections and to GvHD and infections following repeat transplants. Long-term survivors in both patient groups remain with few exceptions free of late complications and with stable graft function and complete donor cell chimerism. Based on our findings, we recommend early and prompt treatment of each diagnosed WAS patient if an HLA-matched, related or unrelated, donor can be identified. If this is not the case, HLA-nonidentical donor transplantation represents an alternative to be considered early in patients with severe disease.

Outcome in patients with Wiskott-Aldrich syndrome following stem cell transplantation: an analysis of 57 patients in Japan.

A total of 57 patients with Wiskott-Aldrich syndrome (WAS) were studied after undergoing stem cell transplantation (SCT) in Japan between January 1985 and December 2004. Eleven patients received transplants from human leucocyte antigen (HLA)-matched related donors, 10 from HLA-mismatched related donors, 21 from unrelated bone marrow donors, and 15 from unrelated cord blood donors. Nine of the 57 patients rejected the initial graft. The overall 5-year survival rate was 73.7% and the 5-year failure-free survival rate was 65.7% (failure was defined as rejection or death). The overall 5-year survival rates for patients receiving bone marrow and cord blood from unrelated donors were both 80.0%. Based on univariate analysis, the factors associated with poor survival were: transplantation from an HLA-mismatched related donor, patient age of more than 5 years at the time of transplantation, and a conditioning regimen other than busulfan and cyclophosphamide (BU-CY) or busulfan, cyclophosphamide and antithymocyte globulin (BU-CY-ATG). In a multivariate analysis, a conditioning regimen other than BU-CY and BU-CY-ATG was the only independent factor associated with transplantation failure. Given the improved outcome for WAS patients following transplantation from an unrelated donor, we conclude that patients with WAS should receive SCT as soon as possible after diagnosis.

Autoimmunity in Wiskott-Aldrich syndrome: risk factors, clinical features, and outcome in a single-center cohort of 55 patients.

OBJECTIVES: To evaluate the occurrence of autoimmune and inflammatory complications in Wiskott-Aldrich syndrome (WAS) and to determine risk factors and the prognosis of such complications with the aim of improving the definition of treatment options. METHODS: We reviewed the records of 55 patients with WAS evaluated at Necker-Enfants Malades Hospital (Paris) from 1980 to 2000. RESULTS: Forty patients (72%) had at least 1 autoimmune or inflammatory complication. Autoimmune hemolytic anemia was detected in 20 cases (36%); in all cases, onset occurred before the age of 5 years. Other complications included neutropenia (25%), arthritis (29%), skin vasculitis (22%), cerebral vasculitis (7%), inflammatory bowel disease (9%), and renal disease (3%). The median survival of the entire population was 14.5 years. Two autoimmune complications and 1 biological factor were predictive of a poor prognosis in this population: autoimmune hemolytic anemia, severe thrombocytopenia recurring after splenectomy, and high serum immunoglobulin M (IgM) levels before splenectomy. Autoimmune hemolytic anemia was significantly more observed in patients with high serum IgM level. CONCLUSIONS: High serum IgM concentration before splenectomy was identified as a risk factor for autoimmune hemolytic anemia; however, it must be confirmed. Autoimmune hemolytic anemia and severe thrombocytopenia recurring after splenectomy were 2 indicators of a poor prognosis. Those results suggest that patients with WAS and IgM levels more than mean + 2 standard deviations before splenectomy should be placed under strict surveillance. Furthermore, severe autoimmune complications should lead, as early as possible, to hematopoietic stem cell transplantation using the best available donor.

A defect in hematopoietic stem cell migration explains the nonrandom X-chromosome inactivation in carriers of Wiskott-Aldrich syndrome.

A defect in cell trafficking and chemotaxis plays an important role in the immune deficiency observed in Wiskott-Aldrich syndrome (WAS). In this report, we show that marrow cells from WAS protein (WASP)-deficient mice also have a defect in chemotaxis. Serial transplantation and competitive reconstitution experiments demonstrated that marrow cells, including hematopoietic progenitors and stem cells (HSCs), have decreased homing capacities that were associated with a defect in adhesion to collagen. During development, HSCs migrate from the liver to the marrow and the spleen, prompting us to ask if a defect in HSC homing during development may explain the skewed X-chromosome inactivation in WAS carriers. Preliminary evidence has shown that, in contrast to marrow progenitor cells, fetal liver progenitor cells from heterozygous females had a random X-chromosome inactivation. When fetal liver cells from WASP-carrier females were injected into irradiated recipients, a nonrandom inactivation of the X-chromosome was found at the level of hematopoietic progenitors and HSCs responsible for the short- and long-term hematopoietic reconstitution. Therefore, the mechanism of the skewed X-chromosomal inactivation observed in WAS carriers may be related to a migration defect of WASP-deficient HSCs.

[Wiskott-Aldrich syndrome: the possibilities of diagnosis and treatment]. / Wiskott-Aldrich sindromas: diagnozavimo bei gydymo galimybes.

Wiskott-Aldrich syndrome is congenital X-linked immunodeficiency characterized by frequent infections, thrombocytopenia with small platelets, eczema and increased risk of autoimmune disorders and malignancies. This article is review of Wiskott-Aldrich syndrome actual diagnostics and treatment problems. Diagnostics problems exist due to clinical heterogenity of this syndrome, which is caused by mutations of the responsible gene. Recent 15-year studies showed, that bone marrow transplantations or use of cord blood as a source of stem cells prolonged median survival from 6.5 to 11 years. However, widespread use of splenectomy, intravenous immune globulin and prophylactic antibiotics did not change survival or appearance of infections, bleeding and autoimmune diseases. An attractive option for Wiskott-Aldrich syndrome is gene therapy, which leads to complete cure.

Impact of donor type on outcome of bone marrow transplantation for Wiskott-Aldrich syndrome: collaborative study of the International Bone Marrow Transplant Registry and the National Marrow Donor Program.

Human leukocyte antigen (HLA)-identical sibling bone marrow transplantation is an effective treatment for Wiskott-Aldrich syndrome. However, most children with this disease lack such donors and many patients receive transplants from alternative donors. This study compared outcomes of HLA-identical sibling, other related donor, and unrelated donor transplantation for Wiskott-Aldrich syndrome. The outcome of 170 transplantations for Wiskott-Aldrich syndrome, from 1968 to 1996, reported to the International Bone Marrow Transplant Registry and/or National Marrow Donor Program were assessed. Fifty-five were from HLA-identical sibling donors, 48 from other relatives, and 67 from unrelated donors. Multivariate proportional hazards regression was used to compare outcome by donor type and identify other prognostic factors. Most transplant recipients were younger than 5 years (79%), had a pretransplantation performance score greater than or equal to 90% (63%), received pretransplantation preparative regimens without radiation (82%), and had non-T-cell-depleted grafts (77%). Eighty percent received their transplant after 1986. The 5-year probability of survival (95% confidence interval) for all subjects was 70% (63%-77%). Probabilities differed by donor type: 87% (74%-93%) with HLA-identical sibling donors, 52% (37%-65%) with other related donors, and 71% (58%-80%) with unrelated donors (P =.0006). Multivariate analysis indicated significantly lower survival using related donors other than HLA-identical siblings (P =.0004) or unrelated donors in boys older than 5 years (P =.0001), compared to HLA-identical sibling transplants. Boys receiving an unrelated donor transplant before age 5 had survivals similar to those receiving HLA-identical sibling transplants. The best transplantation outcomes in Wiskott-Aldrich syndrome are achieved with HLA-identical sibling donors. Equivalent survivals are possible with unrelated donors in young children.

Wiskott-Aldrich syndrome: fatal consequences of splenectomy in an unrecognised attenuated variant.

Monozygotic twin males with an attenuated variant of the Wiskott-Aldrich syndrome (WAS) are described. Diagnostic features included moderate thrombocytopenia with small platelet size and abnormal platelet aggregation responses, chronic eczema, depressed serum IgM and low isoagglutinin titre. Splenectomy was performed on one twin at age seven years who survived a complicating pneumococcal septicaemia ten days after the procedure, but who succumbed to fulminating infection three years later. The importance of recognising the attenuated variants of WAS is discussed.

Phagocyte function and immunological findings in a Wiskott-Aldrich syndrome long-term survivor.

The case reported concerns a 19-year-old man who presented with clinical and laboratory findings compatible with the Wiscott-Aldrich Syndrome. Our patients is the eighth reported case of a long-term survivor with this syndrome. Immunologic studies revealed, in spite of a normal lymphocyte number, an impaired delayed hypersensitivity and a failure of response to mitogens and irradiated allogeneic cells. IgE and IgA levels were high while IgM levels were low. Studies of phagocytic cells showed normal phagocytosis, candidacidal activity, IgG receptors and phagocytic metabolic burst. However, the patient's neutrophils and monocytes responded poorly to chemoattractants and the serum generated less chemotactic activity than normal sera. Detailed studies revealed the presence in the patient's serum of 2 different inhibitors of chemotaxis: a cell-directed inhibitor and an inhibitor of chemotactic factors.

The Wiskott-Aldrich syndrome in the United States and Canada (1892-1979).

Information was collected on 301 cases of the Wiskott-Aldrich syndrome in the United States and Canada Examination of available medical records, death certificates and published case reports on these patients showed that they came from a wide geographic area and many diverse ethnic and racial groups. No significant difference was found in the incidence of cases born between 1947 and 1976; the overall rate was 4.0 per million live male births in the United States. Median survival has increased with time from eight months for patients born before 1935 to 6.5 years for those born after 1964. Seventy-six of the 301 patients (25%) were still alive at last follow-up and ranged in age from 1 to 36 years with a median of 10 years. Causes of death were primarily limited to infections or bleeding, but malignancy represented a significant problem. Twelve percent of the group (36 of 301) developed malignancy, the predominant types being lymphorecticular tumors (23 of 36) and leukemia (7 of 36). The overall relative risk for malignancy was found to be greater than 100 times that of the general population and was found to increase with increasing age.

Splenectomy in the management of the thrombocytopenia of the Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome is an X-linked immunodeficiency disorder consisting of the triad of frequent infections, eczema, and profound thrombocytopenia. We evaluated the effects of splenectomy on hemostatic improvement and subsequent clinical course in 16 patients with the Wiskott-Aldrich syndrome. All 16 had an increase in platelet counts to at least 100,000 per cubic millimeter after splenectomy, with the mean increasing from 19,900 per cubic millimeter preoperatively to 262,700 per cubic millimeter after splenectomy. In addition, platelet size, which is characteristically small in this disease, also became normal. Survival after splenectomy correlated with the prophylactic use of antibiotics. Five of seven patients not taking prophylactic antibiotics died of sepis within 33 months of surgery. The mean survival of the nine patients maintained with prophylactic antibiotics, however, was at least 91.4 months, with six of these patients still alive an average of 11.0 years or more after splenectomy. Thus, splenectomy is a useful therapy for a major cause of morbidity and mortality in this complex syndrome.