Plasminogen Activator Inhibitor-1 4G/5G Promoter Polymorphism in Indian Patients with Deep Vein Thrombosis.

A single guanosine deletion/insertion (4G/5G) polymorphism in the promoter region of plasminogen activator inhibitor-1 (PAI-1) gene encoding PAI-1 protein has been investigated in deep vein thrombosis (DVT) patients. The association between PAI-1 4G/5G polymorphism and increased risk of DVT has been reported in some studies, while others have reported a lack of association. The present study aimed to investigate if the PAI-1 4G/5G polymorphism is associated with an increased risk of DVT in the Indian population and to assess its association with thrombophilic risk factors. Fifty-two adult patients with a history of chronic or recurrent DVT and 52 healthy adult controls were genotyped for PAI-1 4G/5G polymorphism. Plasma levels of PAI-1 and other thrombophilic risk factors were also measured. PAI-1 4G/5G polymorphism was not significantly associated with an increased risk of DVT. Protein C deficiency was significantly associated with the 4G/4G genotype. Patients with the 4G/4G genotype had significantly reduced PAI-1 levels as compared to the controls. PAI-1 4G/5G polymorphism did not significantly contribute to an increased risk of DVT in the Indian population. However, in the presence of thrombophilic risk factor abnormalities, the risk of DVT is increased in individuals with the 4G/4G genotype in the Indian cohort. Supplementary Information: The online version contains supplementary material available at 10.1007/s12288-023-01660-3.

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.

Transmission patterns of C1-INH deficiency hereditary angioedema favors a wild-type male offspring: Our experience at Chandigarh, India.

BACKGROUND: Deficiency of C1-inhibitor (C1-INH) protein, caused by pathogenic variants in the Serpin family G member 1 (SERPING1) gene, is the commonest pathophysiological abnormality (in ∼95 % cases) in patients with hereditary angioedema (HAE). C1-INH protein provides negative control over kallikrein-kinin system (KKS). Although the inheritance of the HAE-C1-INH is autosomal dominant, female predominance has often been observed in patients with HAE. OBJECTIVE: To analyze the risk of transmission of SERPING1 gene variant from father or mother to their offspring. METHODS: Pedigree charts of 42 families with a confirmed diagnosis of HAE-C1-INH and a pathogenic variant in the SERPING1 gene were analysed. Patients with HAE who had had at least one child were included for analyses to assess the risk of transmission from the father or mother to their offspring. RESULTS: Overall, 49 % (189/385) of all offspring inherited the genetic defect. In the subgroup analyses, 54.8 % (90/164) female offspring and 44.8 % (99/221; p < 0.02) male offspring inherited the genetic defect. Inheritance of the genetic defect was significantly lower in male offspring. Fathers with SERPING1 gene variant had a statistically significant skewed transmission of the wild type to the male offspring as compared to the variant (57.8 % wild type vs. 42.1 % variant; p < 0.02), whereas no statistically significant difference was found when a father transmitted the variant to a female offspring. Mothers with SERPING1 gene variant had no statistically significant difference in variant transmission to male or female offsprings. CONCLUSION: Results of the study suggest that the transmission pattern of SERPING1 gene variant favours the transmission of wild-type alleles in males, especially when the father is the carrier; hence, overall, fewer males and more female offspring inherited the variant. This could be because of a selection of wild-type male sperms during spermatogenesis, as the KLK system has been reported to play a crucial role in the regulation of spermatogenesis. Although, a similar pattern was observed in the maternal transmission of the SERPING1 gene variant; the difference was not statistically significant, likely because of a small sample size.

X-Linked Lymphoproliferative Syndrome: A Spectrum of Clinical and Immunological Profile and Novel Pathogenic Variants from Chandigarh, India.

INTRODUCTION: X-linked lymphoproliferative syndrome (XLP) is a rare primary immune deficiency. Two types of XLP have been described: XLP-1 and XLP-2. METHODS: We found 7 patients with XLP (3 had XLP-1 and 4 had XLP-2) after reviewing the data from Pediatric Immunodeficiency Clinic from 1997 to 2021. RESULTS: Mean age at diagnosis was 3.8 years, and mean delay in diagnosis was 2.6 years. Five patients had recurrent episodes of infections. Four patients developed at least one episode of hemophagocytic lymphohistiocytosis (HLH) (2 with XLP-1 and 2 with XLP-2). Of these, 2 had recurrent HLH (both with XLP-2). Epstein-Barr virus (EBV) infection was detected in 2 (1 with XLP-1 and 1 with XLP-2). Both these patients had HLH. One child with XLP-2 had inflammatory bowel disease. Hypogammaglobulinemia was seen in 3 (2 with XLP-1 and 1 with XLP-2). Genetic analysis showed previously reported variants in 5, while 2 had novel variants (one in exon 7 of XIAP gene [c.1370dup p.Asn457Lysfs Ter16] and other had splice site variant in intron 1 of SH2D1A gene [c.138-2_138-1insG]). Episodes of HLH were managed with intravenous immunoglobulin (IVIg), methylprednisolone, oral prednisolone, cyclosporine, and rituximab. Inflammatory bowel disease was managed using oral prednisolone and azathioprine. One patient underwent haploidentical hematopoietic stem cell transplantation. One child with XLP-2 and WAS died because of fulminant pneumonia. DISCUSSION/CONCLUSIONS: XLP should be considered as a strong possibility in any patient with features of HLH, repeated infections with hypogammaglobulinemia, persistent EBV infection, and early-onset IBD.

Clinical, immunological and molecular profiles of DOCK8 deficiency in six patients from a tertiary care centre in North India.

BACKGROUND: Dedicator of cytokinesis protein 8 (DOCK8) deficiency is an autosomal recessive form of combined immunodeficiency. This rare disorder is characterized by an increased predisposition to allergy, autoimmunity and malignancies. OBJECTIVES: To analyse clinical, immunological and molecular profiles of patients with DOCK8 deficiency. METHODS: Clinic records of all patients attending the primary immunodeficiency clinic from 2018 to 2021 were reviewed. Six patients from five families were found to have DOCK8 deficiency. RESULTS: Median age at diagnosis was 7.5 years (range 2-13), with a male/female ratio of 5 : 1. Among the six patients, recurrent eczematous skin lesions were the predominant cutaneous manifestation, present in five patients (83%). Warts and molluscum contagiosum were evident in two patients (33%) and one patient (16%), respectively. Two patients had recalcitrant prurigo nodularis lesions and two had epidermodysplasia verruciformis-like lesions. Food allergies and asthma were reported by one patient each. Of the six patients, recurrent sinopulmonary infections were detected in five (83%). Epstein-Barr virus-driven non-Hodgkin lymphoma with liver metastases was the only case of malignancy, in a 4-year-old boy. IgE was elevated in all patients. Lymphopenia and eosinophilia were observed in three patients (50%) and five patients (83.3%), respectively. Genetic analysis showed DOCK8 pathogenic variants in all patients: homozygous deletion mutations in two patients, compound heterozygous deletion mutations in one, and homozygous nonsense mutations in two. A novel pathogenic homozygous missense variant in the DOCK8 gene was identified in one patient. CONCLUSIONS: DOCK8 deficiency should be considered as a possibility in any patient with early onset eczema, cutaneous viral infections and increased predisposition to allergy, autoimmunity and malignancy.

Delay in diagnosis is the most important proximate reason for mortality in hereditary angio-oedema: our experience at Chandigarh, India.

BACKGROUND: Hereditary angio-oedema (HAE) is a rare autosomal dominant disorder characterized clinically by recurrent episodes of nonpruritic subcutaneous and/or submucosal oedema. Laryngeal oedema is the commonest cause of mortality in patients with HAE. Prior to the availability of first-line treatment options for the management of HAE, mortality was as high as 30%. Mortality has significantly declined in countries where first-line treatment options are available and patients can access these therapies. There is a paucity of literature on the outcomes of patients with HAE in developing countries where availability of and access to first-line treatment options are still a challenge. OBJECTIVES: To report our experience on mortality in patients with HAE and to report factors associated with the death of these patients. METHODS: We carried out a record review of all patients diagnosed with HAE between January 1996 and August 2022. Families with HAE who had reported the death of at least one family member/relative from laryngeal oedema were studied in detail. RESULTS: Of the 65 families (170 patients) registered in the clinic, 16 families reported the death of at least one family member/relative from laryngeal oedema (total of 36 deaths). Of these 16 families, 14 reported that 1 or more family members had experienced at least 1 attack of laryngeal oedema. One patient died during follow-up when she was taking long-term prophylaxis with stanozolol and tranexamic acid, while the remaining 35 patients were not diagnosed with HAE at the time of their death. At the time of death of all 36 patients, at least 1 other family member had symptoms suggestive of HAE, but the diagnosis was not established for the family. CONCLUSIONS: To our knowledge, this is the largest single-centre cohort of patients with HAE in India reporting mortality data and factors associated with death in these families. The delay in diagnosis is the most important reason for mortality.

Tuberculosis and Bacillus Calmette-Guérin Disease in Patients with Chronic Granulomatous Disease: an Experience from a Tertiary Care Center in North India.

Chronic granulomatous disease (CGD) is a phagocytic defect characterized by recurrent bacterial and fungal infections. We report clinical profile of patients with CGD and mycobacterial infections in a cohort from North India. A review of clinical and laboratory records was carried out for patients with CGD registered at our center between 1990 and 2021. Of the 99 patients with CGD, 22 had mycobacterial infections-Mycobacterium tuberculosis and M. bovis-BCG in 11 each. Among the children with M. bovis-BCG infection, 6 had localized and 5 had disseminated BCG disease. Median age at onset of symptoms and diagnosis of BCG disease was 5 months and 15 months, respectively. While disseminated forms of BCG were noted only in CYBB defect, none of the patients with NCF1 defect developed complications due to BCG vaccine. A recurring radiological feature was left axillary lymph node calcification, which was present in around 50% of CGD patients with BCG infections. Of 11 patients with tuberculosis, pulmonary, pleuro-pulmonary, abdominal, and disseminated forms were present in 6, 1, 2, and 2, respectively. Median age at onset of symptoms and diagnosis of tuberculosis was 129 months and 130 months, respectively. Molecular defects were identified in CYBB (5), NCF1 (4), and CYBA (1). Incidence of tuberculosis and BCG-related complications in patients with CGD is higher than the normal population. Screening for CGD is warranted in any patient with adverse reactions to BCG vaccination, calcification of left axillary lymph node, and persistent, recurrent or disseminated forms of tuberculosis.

Intravenous Immunoglobulin in Kawasaki Disease-Evolution and Pathogenic Mechanisms.

Kawasaki disease (KD) is an acute vasculitis of childhood that affects the medium vessels with a special predilection to the involvement of coronary arteries. The major morbidity of this disease is due to coronary artery aneurysm, which occurs in about 25-30% of untreated cases. For decades now, intravenous immunoglobulin (IVIg) has consistently been shown to reduce the risk of CAAs to less than 5%. However, the mechanism of immunomodulation remains unclear. Several studies on the role of IVIg in the modulation of toll-like receptor pathways, autophagy, and apoptosis of the mononuclear phagocytic system, neutrophil extracellular trap, and dendritic cell modulation suggest a modulatory effect on the innate immune system. Similarly, certain studies have shown its effect on T-cell differentiation, cytokine release, and regulatory T-cell function. In this review, we discuss the potential mechanisms underlying the immunomodulatory actions of IVIg in patients with Kawasaki disease. Furthermore, we provide a summary of the evidence regarding various infusion protocols and dosages utilized in the treatment of KD patients.

Kawasaki Disease and Inborn Errors of Immunity: Exploring the Link and Implications.

The exact etiopathogenesis of Kawasaki disease (KD), the most common childhood vasculitis, remains unknown; however, an aberrant immune response, possibly triggered by an infectious or environmental agent in genetically predisposed children, is believed to be the underlying pathogenetic mechanism. Patients with inborn errors of immunity (IEI) are predisposed to infections that trigger immune dysregulation due to an imbalance in various arms of the immune system. KD may develop as a complication in both primary and secondary immunodeficiencies. KD may occur either at disease presentation or have a later onset in IEIs. These include X-linked agammaglobulinemia (XLA), selective IgA deficiency, transient hypogammaglobulinemia of infancy; Wiskott-Aldrich syndrome (WAS), hyper IgE syndrome (HIES); chronic granulomatous disease (CGD), innate and intrinsic immunity defects, and autoinflammatory diseases, including PFAPA. Hitherto, the association between KD and IEI is confined to specific case reports and case series and, thus, requires extensive research for a comprehensive understanding of the underlying pathophysiological mechanisms. IEIs may serve as excellent disease models that would open new insights into the disease pathogenesis of children affected with KD. The current review highlights this critical association between KD and IEI supported by published literature.

Impact of COVID-19 Pandemic on Clinical Care of Patients and Psychosocial Health of Affected Families with Chronic Granulomatous Disease: an Observational Study from North India.

Day-to-day clinical management of patients with inborn errors of immunity, including chronic granulomatous disease (CGD), has been affected by the coronavirus disease-2019 (COVID-19) pandemic. There is a dearth of information on impact of this pandemic on clinical care of children with CGD and psychological profile of the caretakers. Among the 101 patients with CGD followed up in our center, 5 children developed infection/complications associated with COVID-19. Four of these children had a mild clinical course, while 1 child developed features of multisystem inflammatory syndrome in children (MISC) requiring intravenous glucocorticoids. Parents and caretakers of CGD patients (n = 21) and 21 healthy adults with similar ages and genders were also evaluated on the following scales and questionnaires: COVID-19 Fear Scale (FCV 19S), Impact of Event Scale (IES-R), Depression, Anxiety, and Stress Scale (DASS 21), Preventive COVID-19 Behavior Scale (PCV 19BS), and a "COVID-19 Psychological wellbeing questionnaire." Median age of the parents/caregivers was 41.76 years (range: 28-60 years). Male:female ratio was 2:1. In the study group, 71.4% had higher IES scores compared to 14.3% in controls. The caregivers had a high prevalence of stress, anxiety, avoidance behavior, and depression compared to controls (p < 0.001). Children with CGD have had predominantly mild infection with COVID-19; however, caregivers/parents of these children were at risk of developing psychological distress. The COVID-19 pandemic has brought to light the importance of patients' and caretakers' mental health which needs periodic assessment and appropriate interventions.

Microbiome and Its Dysbiosis in Inborn Errors of Immunity.

Inborn errors of immunity (IEI) can present with infections, autoimmunity, lymphoproliferation, granulomas, and malignancy. IEIs are due to genetic abnormalities that disrupt normal host-immune response or immune regulation. The microbiome appears essential for maintaining host immunity, especially in patients with a defective immune system. Altered gut microbiota in patients with IEI can lead to clinical symptoms. Microbial dysbiosis is the consequence of an increase in pro-inflammatory bacteria or a reduction in anti-inflammatory bacteria. However, functional and compositional differences in microbiota are also involved. Dysbiosis and a reduced alpha-diversity are well documented, particularly in conditions like common variable immunodeficiency. Deranged microbiota is also seen in Wiskott-Aldrich syndrome, severe combined immunodeficiency, chronic granulomatous disease, selective immunoglobulin-A deficiency, Hyper IgE syndrome (HIGES), X-linked lymphoproliferative disease-2, immunodysregulation, polyendocrinopathy, enteropathy, x-linked syndrome, and defects of IL10 signalling. Distinct gastrointestinal, respiratory, and cutaneous symptoms linked to dysbiosis are seen in several IEIs, emphasizing the importance of microbiome identification. In this study, we discuss the processes that maintain immunological homeostasis between commensals and the host and the disruptions thereof in patients with IEIs. As the connection between microbiota, host immunity, and infectious illnesses is better understood, microbiota manipulation as a treatment strategy or infection prevention method would be more readily employed. Therefore, optimal prebiotics, probiotics, postbiotics, and fecal microbial transplantation can be promising strategies to restore the microbiota and decrease disease pathology in patients with IEIs.

Kawasaki disease and the environment: an enigmatic interplay.

Kawasaki disease (KD) is a common systemic vasculitis of childhood. Although it has been almost 6 decades since Dr. Tomisaku Kawasaki reported the first case series of KD, the underlying cause remains a mystery. KD is a self-limiting disease. However, a dreaded complication is development of coronary artery abnormalities (CAAs). KD is the most common cause of acquired heart disease in children in the developed world and is being increasingly reported from developing countries too. Over the years, significant observations have been made about epidemiology of KD. It usually affects children below 5, has male preponderance and has significantly higher incidence in North East Asian countries. While several hypotheses have been proffered for etiology of KD, none have been conclusive. These include associations of KD epidemics in Japan and the United Stated with changes in tropospheric wind patterns suggesting wind-borne agents, global studies showing peaks of incidence related to season, and increased rates in populations with a higher socioeconomic profile related to hygiene hypothesis and vaccination. Furthermore, the self-limiting, febrile nature of KD suggests an infectious etiology, more so with sudden decline noted in cases in Japan with onset of COVID-19 mitigation measures. Finally, single nucleotide polymorphisms have been identified as possible risk alleles in patients with KD and their significance in the pathogenesis of this disease are also being defined. The purpose of this review is to elucidate the puzzling associations of KD with different environmental factors. Looking at patterns associated with KD may help us better predict and understand this disease.

Challenges in the diagnosis of periodic fever, aphthous stomatitis, pharyngitis, and adenitis syndrome in developing countries-A decade of experience from North India.

Background: Reports of periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome from developing countries are sparse. Recognizing PFAPA is often challenging in these regions due to a higher incidence of infectious illnesses and significant resource constraints. Herein, we present our experience from North India regarding the diagnosis and management of PFAPA syndrome. Methods: We reviewed cases of non-monogenic periodic fever syndrome diagnosed at our center from January 2011 to December 2021. A total of 17 children who fulfilled the Marshall criteria for PFAPA syndrome were included. Data regarding basic clinical features, treatment/outcome, and performance of the recently proposed Eurofever/PRINTO and Takeuchi criteria were analyzed. Results: Besides recurrent fever, the triad of oral aphthae, pharyngitis, and adenitis was noted in only 18% of patients. Episodes of exudative pharyngitis/tonsillitis were documented in 24%. These figures were lower than the values reported from developed countries. The Takeuchi and Eurofever/PRINTO criteria were fulfilled in 76% and 71% cases, respectively. In addition to antipyretics and supportive care, intermittent steroid therapy was the main treatment modality used. Additional treatment with colchicine (n = 3) and thalidomide (n = 1) was used successfully in a few patients. Before the diagnosis of PFAPA, all patients had received multiple courses of antimicrobials (without microbiological confirmation). These included multiple courses of antibacterials for fever, pharyngotonsillitis, and/or cervical adenitis in all patients and antivirals for fever and aphthous stomatitis in a patient. Empiric antitubercular therapy had also been administered in two patients. Conclusions: A significant proportion of patients with PFAPA seem to remain undiagnosed in the Indian subcontinent. Increased awareness and improvement in basic healthcare facilities are crucial in enhancing the recognition of PFAPA, which would eliminate the unprecedented scale of undesirable antimicrobial use in such children.

Autoimmune Cytopenias in Common Variable Immunodeficiency Are a Diagnostic and Therapeutic Conundrum: An Update.

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency (PID). CVID is a heterogenous condition and clinical manifestations may vary from increased susceptibility to infections to autoimmune manifestations, granulomatous disease, polyclonal lymphoproliferation, and increased risk of malignancy. Autoimmune manifestations may, at times, be the first and only clinical presentation of CVID, resulting in diagnostic dilemma for the treating physician. Autoimmune cytopenias (autoimmune haemolytic anaemia and/or thrombocytopenia) are the most common autoimmune complications seen in patients with CVID. Laboratory investigations such as antinuclear antibodies, direct Coomb's test and anti-platelet antibodies may not be useful in patients with CVID because of lack of specific antibody response. Moreover, presence of autoimmune cytopenias may pose a significant therapeutic challenge as use of immunosuppressive agents can be contentious in these circumstances. It has been suggested that serum immunoglobulins must be checked in all patients presenting with autoimmune cytopenia such as immune thrombocytopenia or autoimmune haemolytic anaemia. It has been observed that patients with CVID and autoimmune cytopenias have a different clinical and immunological profile as compared to patients with CVID who do not have an autoimmune footprint. Monogenic defects have been identified in 10-50% of all patients with CVID depending upon the population studied. Monogenic defects are more likely to be identified in patients with CVID with autoimmune complications. Common genetic defects that may lead to CVID with an autoimmune phenotype include nuclear factor kappa B subunit 1 (NF-kB1), Lipopolysaccharide (LPS)-responsive beige-like anchor protein (LRBA), cytotoxic T lymphocyte antigen 4 (CTLA4), Phosphoinositide 3-kinase (PI3K), inducible T-cell costimulatory (ICOS), IKAROS and interferon regulatory factor-2 binding protein 2 (IRF2BP2). In this review, we update on recent advances in pathophysiology and management of CVID with autoimmune cytopenias.

Lymphoproliferation in Inborn Errors of Immunity: The Eye Does Not See What the Mind Does Not Know.

Inborn errors of immunity (IEIs) are a group of heterogeneous disorders characterized by a broad clinical spectrum of recurrent infections and immune dysregulation including autoimmunity and lymphoproliferation (LP). LP in the context of IEI may be the presenting feature of underlying immune disorder or may develop during the disease course. However, the correct diagnosis of LP in IEI as benign or malignant often poses a diagnostic dilemma due to the non-specific clinical features and overlapping morphological and immunophenotypic features which make it difficult to treat. There are morphological clues to LP associated with certain IEIs. A combination of ancillary techniques including EBV-associated markers, flow cytometry, and molecular assays may prove useful in establishing a correct diagnosis in an appropriate clinical setting. The present review attempts to provide comprehensive insight into benign and malignant LP, especially the pathogenesis, histological clues, diagnostic strategies, and treatment options in patients with IEIs.

Bone Marrow Metastasis in a Suspected Case of Angiosarcoma Unravelled by Immunohistochemistry.

A 40-year-old female presented with progressive fatigue and left upper abdominal discomfort for 1 month. CT scan revealed ill-defined hypervascular lesions in the liver and diffuse enlargement of the spleen. She had severe anemia with leukoerythroblastic reaction. Bone marrow smears revealed clusters and discrete spindle cells, few plump and round cells. Trephine biopsy revealed an infiltrative spindle-cell neoplasm replacing the marrow with the focal presence of epithelioid cell clusters. On immunostaining, the tumor cells were positive for CD34, CD31, Friend Leukemia Virus Integration-1 (FLI1), and vimentin, consistent with metastatic angiosarcoma. There were multiple small aggregates of 5-10 MIB-1 positive tumor cells (overall positivity < 1%). She succumbed to her illness before initiation of any therapy. Bone marrow metastasis of angiosarcoma is extremely rare. The aggressive clinical course and judicious use of immunohistochemical markers are required for definitive diagnosis.

Deficiency of Human Adenosine Deaminase Type 2 - A Diagnostic Conundrum for the Hematologist.

Deficiency of adenosine deaminase type 2 (DADA2) was first described in 2014 as a monogenic cause of polyartertitis nodosa (PAN), early onset lacunar stroke and livedo reticularis. The clinical phenotype of DADA2 is, however, very broad and may involve several organ systems. Apart from vasculitis, children may present with i) Hematological manifestations (ii) Lymphoproliferation and iii) Immunodeficiencies. Patients with DADA2 can have variable patterns of cytopenias and bone marrow failure syndromes. Patients with DADA2 who have predominant haematological manifestations are associated with ADA2 gene variants that result in minimal or no residual ADA2 activity. Lymphoproliferation in patients with DADA2 may range from benign lymphoid hyperplasia to lymphoreticular malignancies. Patients may present with generalized lymphadenopathy, splenomegaly, autoimmune lymphoproliferative syndrome (ALPS) like phenotype, Hodgkin lymphoma, T-cell large granular lymphocytic infiltration of bone marrow and multicentric Castleman disease. Immunodeficiencies associated with DADA are usually mild. Affected patients have variable hypogammaglobulinemia, decrease in B cells, low natural killer cells, common variable immunodeficiency and rarely T cell immunodeficiency. To conclude, DADA2 has an extremely variable phenotype and needs to be considered as a differential diagnosis in diverse clinical conditions. In this review, we describe the evolving clinical phenotypes of DADA2 with a special focus on haematological and immunological manifestations.