Combined De-Novo Mutation and Non-Random X-Chromosome Inactivation Causing Wiskott-Aldrich Syndrome in a Female with Thrombocytopenia

Wiskott-Aldrich Syndrome: A Report of a Rare X-Linked Disorder

Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive genetic disorder marked by eczema, thrombocytopenia, and immunodeficiency. The associated immune dysregulation increases the risk of autoimmune disorders and lymphoid malignancies. WAS results from mutations in the WAS protein gene on the short arm of the X chromosome. Here, we present the case of a seven-month-old male, born to non-consanguineous parents with no significant birth or family history. The child had height, weight, and head circumference below the third percentile for age and presented with recurrent mild upper respiratory infections, mild eczema, and thrombocytopenia. Despite symptomatic treatment and clinical improvement, platelet counts continued to decline. A provisional diagnosis of immune thrombocytopenia was made, and intravenous immunoglobulin was administered, which halted the downward trend but did not improve platelet counts. Autoimmune testing revealed strong positivity for antinuclear antibodies (ANA). Given the early-onset thrombocytopenia, anemia, and failure to thrive, autoimmune lymphoproliferative syndrome was suspected. However, T cell subset analysis was normal. A bone marrow biopsy suggested myelodysplastic syndrome or myeloproliferative neoplasm, but molecular studies were negative. Due to the early-onset autoimmunity and strongly positive ANA, genetic testing via whole exome sequencing confirmed the diagnosis of WAS.

Wiskott-Aldrich syndrome protein expression in female WAS carriers: A flow cytometry study from North India

INTRODUCTION

Wiskott-Aldrich syndrome (WAS) is a rare X-linked inborn error of immunity characterized by microthrombocytopenia, infections, eczema, and increased predisposition to develop autoimmunity and malignancy. Flow cytometric assay for determining WAS protein (WASp) is a rapid and cost-effective tool for detecting patients. However, very few studies described WASp expression in female carriers. Most WAS carriers are clinically asymptomatic. Active screening of female family members helps identify female carriers, distinguish de novo mutations, and to select appropriate donor prior to curative stem cell transplantation. This study was undertaken to evaluate the diagnostic capability of flow cytometry-based WASp expression in peripheral blood cells to identify carriers and compare WASp expression in different blood cell lineages.

PATIENTS AND METHODS

Female patients, heterozygous for WAS gene, were enrolled in this study conducted at Pediatric Allergy Immunology Unit, Advanced Pediatric Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Flow cytometric assessment of WASp expression in lymphocytes, monocytes, and neutrophils was carried out and compared with healthy control and affected patients. The results were expressed in delta (Δ) median fluorescence intensity (MFI) as well as stain index (SI), which is the ratio of ΔMFI of patient and ΔMFI of control.

RESULTS

Thirteen mothers and two sisters of genetically confirmed WAS patients were enrolled in the study. All enrolled females were clinically asymptomatic and did not have microthrombocytopenia. Low WASp expression (SI < 1) was seen in lymphocytes and monocytes in 10 (66.6%) carriers. Females with variants in proximal exons (exons 1 and 2) were found to have lesser expression than those with distal (exons 3-12) variants.

CONCLUSION

Flow cytometry is a rapid, easily available, cost-effective tool for WASp estimation. Lymphocytes followed by monocytes are the best cell lineages for WASp estimation in carrier females. However, genetic testing remains the gold standard, as carrier females with variants in distal exons may have normal WASp expression.

From Mendel to mycoses: Immuno-genomic warfare at the human-fungus interface

Fungi are opportunists: They particularly require a defect of immunity to cause severe or disseminated disease. While often secondary to an apparent iatrogenic cause, fungal diseases do occur in the absence of one, albeit infrequently. These rare cases may be due to an underlying genetic immunodeficiency that can present variably in age of onset, severity, or other infections, and in the absence of a family history of disease. They may also be due to anti-cytokine autoantibodies. This review provides a background on how human genetics or autoantibodies underlie cases of susceptibility to severe or disseminated fungal disease. Subsequently, the lessons learned from these inborn errors of immunity marked by fungal disease (IEI-FD) provide a framework to begin to mechanistically decipher fungal syndromes, potentially paving the way for precision therapy of the mycoses.

Síndrome de Wiskott-Aldrich en España: incidencia, mortalidad y sesgo de género durante 21 años

Antecedentes

El síndrome de Wiskott-Aldrich (SWA) es un raro trastorno ligado al cromosoma X que se considera que afecta predominantemente a varones.

Objetivo

El objetivo de este estudio consistía en investigar la incidencia y la mortalidad intrahospitalaria del SWA en España, así como el sesgo de género.

Métodos

Se llevó a cabo un estudio epidemiológico retrospectivo poblacional en 97 pacientes con SWA diagnosticados en hospitales españoles entre 1997 y 2017, utilizando para ello datos del Sistema Nacional de Vigilancia de Datos Hospitalarios.

Resultados

Nuestros resultados revelaron que la incidencia anual media del SAW en España fue de 1,1 caso por cada 10 millones de habitantes (IC del 95 %, 0,45-2,33). El riesgo relativo fue mayor en los varones que en las mujeres (2,42). El diagnóstico de SWA se establece a una edad más avanzada en las mujeres (mediana de 47 años) que en los varones (mediana de 5,5 años). Únicamente los varones ingresaron en el hospital en al menos 10 ocasiones diferentes y todas las muertes se detectaron en varones. La tasa de mortalidad intrahospitalaria fue del 9,28 % en el SAW y la mayoría de las muertes se asociaron a hemorragia cerebral o infección.

Conclusiones

El SWA, una enfermedad rara, se diagnostica a una edad más avanzada en las mujeres y la mortalidad se observó exclusivamente en varones, asociada en la mayoría de los casos a hemorragia cerebral e infección.

Diagnosis and clinical management of Wiskott-Aldrich syndrome: current and emerging techniques

INTRODUCTION

Wiskott-Aldrich syndrome (WAS) serves as the prototype of how variants in a gene which encodes a protein central to actin cytoskeletal homeostasis can manifest clinically in a variety of ways including infection, atopy, autoimmunity, inflammation, bleeding, neutropenia, non-malignant lymphoproliferation, and malignancy. Despite the discovery of the WAS gene almost 30 years ago, our understanding of the pathophysiological mechanisms underlying WAS continues to unfold.

AREAS COVERED

This review will provide an overview of the approach to the diagnosis of WAS as well as the management of its associated complications. Advances in the use of allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy as well as the associated challenges unique to WAS will be discussed.

EXPERT OPINION

Basic research, combined with clinical research focusing on longitudinal analysis of WAS patients, will help clarify determinants that influence WAS pathogenesis as well as clinical complications and outcomes. Advances in curative approaches including the use of alternative donor HSCT for WAS continue to evolve. Gene therapy employing safer and more effective protocols ensuring full correction of WAS will provide life-saving benefit to WAS patients that are unable to undergo HSCT.

Molecular Mechanisms of Skewed X-Chromosome Inactivation in Female Hemophilia Patients-Lessons from Wide Genome Analyses

Introduction: Hemophilia A (HA) is an X-linked bleeding disorder caused by factor VIII (FVIII) deficiency or dysfunction due to F8 gene mutations. HA carriers are usually asymptomatic because their FVIII levels correspond to approximately half of the concentration found in healthy individuals. However, in rare cases, a carrier may exhibit symptoms of moderate to severe HA primarily due to skewed inactivation of her non-hemophilic X chromosome. Aim: The aim of the study was to investigate X-chromosome inactivation (XCI) patterns in HA carriers, with special emphasis on three karyotypically normal HA carriers presenting with moderate to severe HA phenotype due to skewed XCI, in an attempt to elucidate the molecular mechanism underlying skewed XCI in these symptomatic HA carriers. The study was based on the hypothesis that the presence of a pathogenic mutation on the non-hemophilic X chromosome is the cause of extreme inactivation of that X chromosome. Methods: XCI patterns were studied by PCR analysis of the CAG repeat region in the HUMARA gene. HA carriers that demonstrated skewed XCI were further studied by whole-exome sequencing (WES) followed by X chromosome-targeted bioinformatic analysis. Results: All three HA carriers presenting with the moderate to severe HA phenotype due to skewed XCI were found to carry pathogenic mutations on their non-hemophilic X chromosomes. Patient 1 was diagnosed with a frameshift mutation in the PGK1 gene that was associated with familial XCI skewing in three generations. Patient 2 was diagnosed with a missense mutation in the SYTL4 gene that was associated with familial XCI skewing in two generations. Patient 3 was diagnosed with a nonsense mutation in the NKAP gene that was associated with familial XCI skewing in two generations. Conclusion: Our results indicate that the main reason for skewed XCI in our female HA patients was negative selection against cells with a disadvantage caused by an additional deleterious mutation on the silenced X chromosome, thus complicating the phenotype of a monogenic X-linked disease. Based on our study, we are currently offering the X inactivation test to symptomatic hemophilia carriers and plan to expand this approach to symptomatic carriers of other X-linked diseases, which can be further used in pregnancy planning.

Case Report: Wiskott-Aldrich Syndrome Caused by Extremely Skewed X-Chromosome Inactivation in a Chinese Girl

Wiskott-Aldrich syndrome (WAS) is a rare X-linked immunodeficiency disorder caused by abnormal expression of Wiskott-Aldrich syndrome protein due to WAS gene mutation, which is generally characterized by microthrombocytopenia, eczema, recurrent infections, and high risk of autoimmune complications and hematological malignancies. Although affected males with WAS usually manifest severe symptoms, female carriers have no significant clinical manifestations. Here, we describe a Chinese girl diagnosed with WAS carrying a heterozygous missense mutation in exon 2 of the WAS gene. The patient presented with persistent thrombocytopenia with small platelets and decreased WAS protein detected by flow cytometry and western blot analysis. The methylation analysis of the HUMARA gene displayed an extremely skewed X-chromosome inactivation (SXCI) pattern, where the X-chromosomes bearing normal WAS gene were predominantly inactivated, leaving the mutant gene active. Hence, our results suggest that completely inactivating the unaffected paternal X-chromosomes may be the reason for such phenotype in this female patient. SXCI has important implications for genetic counseling of female carriers with a family history of WAS.

The Phenotype and Treatment of WIP Deficiency: Literature Synopsis and Review of a Patient With Pre-transplant Serial Donor Lymphocyte Infusions to Eliminate CMV

Early diagnosis of primary immunodeficiency disorders (PID) is vital and allows directed treatment, especially in syndromes with severe or profound combined immunodeficiency. In PID patients with perinatal CMV or other opportunistic, invasive infections (e.g., Pneumocystis or Aspergillus), multi-organ morbidity may already arise within the first months of life, before hematopoietic stem cell transplantation (HSCT) or gene therapy can be undertaken, compromising the definitive treatment and outcome. Deficiency of Wiskott-Aldrich syndrome (WAS) protein-interacting protein (WIP deficiency) causes an autosomal recessive, WAS-like syndrome with early-onset combined immunodeficiency that has been described in three pedigrees to date. While WAS typically includes combined immunodeficiency, microthrombocytopenia, and eczema, the clinical and laboratory phenotypes of WIP-deficient patients-including lymphocyte subsets, platelets, lymphocyte proliferation in vitro, and IgE-varied widely and did not entirely recapitulate WAS, impeding early diagnosis in the reported patients. To elucidate the phenotype of WIP deficiency, we provide a comprehensive synopsis of clinical and laboratory features of all hitherto-described patients (n = 6) and WIP negative mice. Furthermore, we summarize the treatment modalities and outcomes of these patients and review in detail the course of one of them who was successfully treated with serial, unconditioned, maternal, HLA-identical donor lymphocyte infusions (DLI) against life-threatening, invasive CMV infection, followed by a TCRαβ/CD19-depleted, treosulfan/melphalan-conditioned, peripheral blood HSCT and repetitive, secondary-prophylactic, CMV-specific DLI with 1-year post-HSCT follow-up. This strategy could be useful in other patients with substantial premorbidity, considered "too bad to transplant," who have an HLA-identical family donor, to eliminate infections and bridge until definitive treatment.

Neuropsychological Profile of a Girl with Wiskott-Aldrich Syndrome

We report the neuropsychological profile of a 6-year-old girl with Wiskott-Aldrich syndrome, a rare X-linked immunodeficiency disorder associated with thrombocytopenia, eczema, recurrent infections, and malignancy. Wiskott-Aldrich syndrome occurs almost exclusively in males and is extremely rare in females, with no known research focused on cognitive and academic functioning in this population. Our patient was referred due to concerns about her memory and academic functioning. She had a history of progressive thrombocytopenia and hematopoietic stem cell transplantation at age 15 months. Standardized measures of intellectual ability, language, visual-spatial and visual-motor skills, attention, memory, and academic achievement were administered. The results showed average to above-average performance in multiple areas of cognitive and academic functioning, with weaknesses in phonological awareness and rapid naming. The advent of hematopoietic stem cell transplantation has led to considerable improvement in the long-term prognosis of children with Wiskott-Aldrich syndrome. Although the impact of this syndrome and related conditions on neurocognitive development is presently unknown, this case highlights both the importance of considering base rates for commonly occurring conditions and the significant role neuropsychology can play in identifying cognitive strengths and weaknesses in the context of the developing brain.

Identification of Intellectual Disability Genes in Female Patients with a Skewed X-Inactivation Pattern

Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males because of the hemizygous state of their X chromosome. Carrier females are generally unaffected because of the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analyzed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6%) had extreme skewing (>90%), which is significantly higher than observed in the general population (3.6%; P = 0.029). Whole-exome sequencing of 19 females with extreme skewing revealed causal variants in six females in the XLID genes DDX3X, NHS, WDR45, MECP2, and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in three of these patients. Moreover, variants likely accounting for skewing only were detected in MED12, HDAC8, and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients.

Haemophilia A and cardiovascular morbidity in a female SHAM syndrome carrier due to skewed X chromosome inactivation

We have recently described a severe haemophilia A and moyamoya (SHAM) syndrome caused by Xq28 deletions encompassing F8 and the BRCC3 familial moyamoya gene. The phenotype includes haemophilia A, moyamoya angiopathy, dysmorphia and hypertension. The genetic analysis of the family of our SHAM patient demonstrated carrier state in proband's mother and sister. The patient's mother is apparently well, whereas his currently 18-years-old sister presents with mild haemophilia A, coarctation of the aorta, hypertension, and ventricular arrhythmia. We performed X chromosome inactivation assay based on HpaII methylation analysis of a polymorphic short tandem repeat (STR) in the X linked AR (androgen receptor) gene and used quantitative real-time RT PCR to measure the expression of genes from the deleted region in proband's family members. We found an extremely skewed X chromosome inactivation pattern in the female members of the family leading to preferential inactivation of the X chromosome without Xq28 deletion in patient's sister. We demonstrated differential expression of the genes from the deleted region in four members of the family, that tightly correlates with the clinical features. In conclusion, we show that the haematologic and cardiovascular morbidity and the discrepancy between patient's sister and mother despite the same genetic lesion are due to skewed X chromosome inactivation leading to clinically relevant differential expression of SHAM syndrome genes. This report highlights the role for BRCC3 in cardiovascular physiology and disease, and demonstrates that in some complex hereditary syndromes full diagnostics may require the examination of both genetic and epigenetic events.

A female patient with incomplete hemophagocytic lymphohistiocytosis caused by a heterozygous XIAP mutation associated with non-random X-chromosome inactivation skewed towards the wild-type XIAP allele

X-linked lymphoproliferative disease (XLP) is a rare inherited immunodeficiency that often leads to hemophagocytic lymphohistiocytosis (HLH). XLP can be classified as XLP1 or XLP2, caused by mutations in SH2D1A and XIAP, respectively. In women, X-chromosome inactivation (XCI) of most X-linked genes occurs on one of the X chromosomes in each cell. The choice of which X chromosome remains activated is generally random, although genetic differences and selective advantage may cause one of the X chromosomes to be preferentially inactivated. Here we describe three patients with pancytopenia, including one female patient, in a Japanese family with a novel XIAP mutation. All three patients exhibited deficient XIAP protein expression, impaired NOD2/XIAP signaling, and augmented activation-induced cell death. In the female patient, the paternally derived X chromosome was non-randomly and exclusively inactivated in her peripheral blood and hair root cells. In contrast to asymptomatic females, this patient exhibied non-random XCI skewed towards the wild-type XIAP allele. This is the first report of a female patient with incomplete HLH resulting from a heterozygous XIAP mutation in association with non-random XCI.

Wiskott-Aldrich syndrome in a girl caused by heterozygous WASP mutation and extremely skewed X-chromosome inactivation: a novel association with maternal uniparental isodisomy 6

Wiskott-Aldrich syndrome (WAS) is an X-linked disease characterized by microthrombocytopenia, eczema and immune deficiency, caused primarily by mutations in the WASP (Wiskott-Aldrich syndrome protein) gene. Female carriers are usually asymptomatic because of the preferential activation of the normal, nonmutated X-chromosome in their hematopoietic cells. We report our observations of a female child with WAS, who displayed symptoms of congenital thrombocytopenia. DNA sequencing analysis of the WASP gene revealed a heterozygous nonsense mutation in exon 10. The expressions of WASP and normal WASP mRNA were defective. We found preferential inactivation of the X-chromosome on which wild-type WASP was located. Single-nucleotide polymorphism microarray testing and the analysis of the polymorphic variable number of tandem repeat regions revealed maternal uniparental isodisomy of chromosome 6 (UPD6). Our results underscore the importance of WASP evaluation in females with congenital thrombocytopenia and suggest that UPD6 might be related to the pathophysiology of nonrandom X-chromosome inactivation.

Identification of novel informative loci for DNA-based X-inactivation analysis

The HUMARA assay, the most common method for evaluation of X-inactivation skewing in blood cells, has been reported to be usable in only about 80% of females, emphasizing the need for alternative methods for testing of HUMARA-uninformative individuals. We conducted an in silico search for potentially polymorphic tri-to-hexanucleotide repeats in the proximity of CpG islands located in 5' regions of X-chromosome genes to design five candidate assays (numbered I, II, III, IV, and V) combining methylation-specific restriction digest with PCR amplification in a manner similar to the HUMARA assay. The results obtained by these assays in 100 healthy females were compared to X-inactivation skewing measured by the AR-MSP method which is based on methylation-specific PCR amplification of the first exon of the AR gene. On the basis of statistical evidence, three of the novel assays (II, IV, and V), which were informative in 18%, 61%, and 55% of females in the cohort, respectively, may be used as alternatives or conjointly with the HUMARA assay to improve its reliability. The three new assays were combined with the HUMARA assay into a novel X-inactivation test leading to the increase of informative females in the cohort from 67% to 96%.

Wiskott-Aldrich syndrome: diagnosis, current management, and emerging treatments

Wiskott–Aldrich syndrome (WAS) is a rare X-linked primary immunodeficiency disorder characterized by the triad of eczema, thrombocytopenia, and severe and often recurrent infections. Despite the rarity of this disorder, our understanding of the molecular and cellular pathogenesis of WAS has continued to increase. Advances in the use of diagnostic tools, the provision of supportive care, and improvements in allogeneic hematopoietic stem cell transplantation have significantly reduced the morbidity and mortality associated with this disorder. Exciting advancements in the care of patients with WAS have also occurred, including the successful application of autologous gene-modified hematopoietic stem cell transplantation.