Autoimmune Cytopenias Are Highly Associated with Inborn Errors of Immunity and They May Be the Initial Presentations in Cases without Severe Infections.

INTRODUCTION: Inborn errors of immunity (IEIs) are inherited disorders that present with increased susceptibility to infections as well as noninfectious complications. Due to the aberrant immune functions of patients with IEI, autoimmune cytopenia (AIC) may be the initial finding, which makes diagnosis a challenge. We aimed to evaluate the clinical course, laboratory findings, and treatment response of AIC in children with IEI. METHODS: Data of children with autoimmune hemolytic anemia (AIHA) and/or immune thrombocytopenic purpura (ITP) were obtained from a retrospective chart review of IEI patients diagnosed and followed in our center. Demographic and clinical features and therapeutic outcomes were evaluated. Immunologic findings were compared between patients with AIHA, ITP, and Evans syndrome (ES). The patients were also divided into two subgroups based on the presence or absence of immune dysregulation diseases (IDDs), and all data were compared between these two groups. RESULTS: Out of 562 patients with IEI, 6% (n: 34) had AIC which were ITP (23.5%), AIHA (35.5%), and ES (41.2%). AIC was the initial finding in 50% of these 34 patients. Patients with ES had a higher mean percentage of CD8+ T lymphocytes than ITP patients (40.77 ± 20.21% vs. 22.33 ± 12.48%, p = 0.011). Patients with IDDs were more likely to develop ES (p = 0.004), lymphoproliferation (p = 0.005), and resistance to first-line therapy (p = 0.021) than other IEI groups. CONCLUSION: This study shows that AIC may be the initial finding of IEI, particularly when lymphoproliferation and resistance to first-line therapy co-occur. Therefore, detailed investigation should be offered to all patients to avoid diagnostic delay.

HAX1-related congenital neutropenia: Long-term observation in paediatric and adult patients enrolled in the European branch of the Severe Chronic Neutropenia International Registry (SCNIR).

HAX1-related congenital neutropenia (HAX1-CN) is a rare autosomal recessive disorder caused by pathogenic variants in the HAX1 gene. HAX1-CN patients suffer from bone marrow failure as assessed by a maturation arrest of the myelopoiesis revealing persistent severe neutropenia from birth. The disorder is strongly associated with severe bacterial infections and a high risk of developing myelodysplastic syndrome or acute myeloid leukaemia. This study aimed to describe the long-term course of the disease, the treatment, outcome and quality of life in patients with homozygous HAX1 mutations reported to the European branch of the Severe Chronic Neutropenia International Registry. We have analysed a total of 72 patients with different types of homozygous (n = 68), compound heterozygous (n = 3), and digenic (n = 1) HAX1 mutations. The cohort includes 56 paediatric (<18 years) and 16 adult patients. All patients were initially treated with G-CSF with a sufficient increase in absolute neutrophil counts. Twelve patients required haematopoietic stem cell transplantation for leukaemia (n = 8) and non-leukaemic indications (n = 4). While previous genotype-phenotype reports documented a striking correlation between two main transcript variants and clinical neurological phenotypes, our current analysis reveals novel mutation subtypes and clinical overlaps between all genotypes including severe secondary manifestations, e.g., high incidence of secondary ovarian insufficiency.

Central nervous system thrombosis in pediatric acute lymphoblastic leukemia in Turkey: A multicenter study.

BACKGROUND: In patients with acute lymphoblastic leukemia (ALL), the risk of thromboembolism increases due to hemostatic changes secondary to the primary disease and due to treatment-related factors. In this multicenter study, we aimed to research the frequency of central nervous system (CNS) thrombosis occurring during treatment, hereditary and acquired risk factors, clinical and laboratory features of patients with thrombosis, treatment approaches, and thrombosis-related mortality and morbidity rates in pediatric ALL patients. PROCEDURE: Pediatric patients who developed CNS thrombosis during ALL treatment from 2010 to 2021 were analyzed retrospectively in 25 different Pediatric Hematology Oncology centers in Türkiye. The demographic characteristics of the patients, symptoms associated with thrombosis, the stage of the leukemia treatment during thrombosis, the anticoagulant therapy applied for thrombosis, and the final status of the patients recorded through electronic medical records were determined. RESULTS: Data from 70 patients with CNS thrombosis during treatment, out of 3968 pediatric patients with ALL, were reviewed. The incidence of CNS thrombosis was 1.8% (venous: 1.5 %; arterial: 0.03%). Among patients with CNS thrombosis, 47 had the event in the first 2 months. Low molecular weight heparin (LMWH) was the most commonly used treatment with a median of 6 months (min-max: 3-28 months). No treatment-related complications occurred. Chronic thrombosis findings occurred in four patients (6%). In five (7%) patients who developed cerebral vein thrombosis, neurological sequelae (epilepsy and neurological deficit) remained. One patient died related to thrombosis, and the mortality rate was 1.4%. CONCLUSION: Cerebral venous thrombosis and, less frequently, cerebral arterial thrombosis may develop in patients with ALL. The incidence of CNS thrombosis is higher during induction therapy than during other courses of treatment. Therefore, patients receiving induction therapy should be monitored carefully for clinical findings suggestive of CNS thrombosis.

Family Knowledge, Attitudes, and Practices Toward Severe Congenital Neutropenia.

Severe congenital neutropenia is a rare disorder. The survival and quality of life of patients radically improved through infection prevention, use of granulocyte colony-stimulating factor, and the appropriate use of antibiotics during infections. The aim of this study was to evaluate the precautions taken by families to prevent infections, the level of knowledge regarding the disease, and the impact of external factors such as education and economic status on behavior and compliance in patients and caregivers in terms of the following treatment protocols. Questionnaires were designed with the aim of determining how the social, cultural, and economic conditions of the families of children with severe congenital neutropenia affected their behavior and knowledge levels. They were completed using one-on-one video interviews with the caregivers. Thirty-one patients from 25 families were enrolled into the study. No correlations between family disease knowledge, parent education levels, working status of the mother, sibling numbers, economic status, ease of hospital access, and/or residential location were found. An increase in disease knowledge of patients and caregivers, as well as proven approaches to living with the disease, would directly correlate to increased life quality and long-term survival rates of patients.

Invasive Fungal Infections in Children With Acute Myeloid Leukemia: A Single-center Experience Over 19 Years.

OBJECTIVE: Invasive fungal infections (IFIs) remain a significant cause of morbidity and mortality in children with acute myeloid leukemia (AML). This study aimed to evaluate the incidence, risk factors, etiology, and outcome of IFIs in children with AML and the effect of mold-active antifungal prophylaxis. MATERIALS AND METHODS: We retrospectively reviewed pediatric patients treated for AML between January 2004 and December 2022. Proven, probable, or possible IFIs were defined using standardized definitions of the European Organization for the Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) classification published at 2008. RESULTS: A total of 298 febrile neutropenia episodes from 78 patients were evaluated. Proven, probable, and possible IFI rates were 3%, 2.6%, and 9.4%, respectively. Profound neutropenia was detected in 18 (58%) and prolonged neutropenia in 20 (64.5%) of the IFI episodes.. Invasive aspergillosis accounted for the majority of IFI episodes; however, non-albicans Candida spp. were the most isolated pathogens in the proven group. Patients with relapsed AML were particularly at risk for the development of IFI ( P =0.02). A significant decrease in IFI episodes was achieved with mold-active antifungal prophylaxis with voriconazole ( P =0.01, odds ratio: 0.288, %95 CI:0.104-0.797). The overall mortality was 35.8%, and the IFI-attributable mortality rate was 25%. In the multivariate analysis, relapsed disease was the most significant risk factor associated with mortality ( P =0.006, odds ratio:4.745; 95% CI: 1.573-14.316). CONCLUSION: Mold-active prophylaxis reduced the rate of IFIs in this cohort however IFI-related mortality was still high as 25% in pediatric AML patients. Relapsed AML was the most significant risk factor associated with mortality.

A rare complication of leukostasis with AML M4 patient: Microcirculatory dysfunction of upper extremities.

BACKGROUND: In children with acute myeloid leukemia, the incidence of hyperleukocytosis is 5-33%. Patients with AML and hyperleukocytosis have a higher early mortality rate than patients with nonhyperleukocytic AML because of the increased risk of severe pulmonary and neurologic complications. Leukapheresis provides rapid cytoreduction and reduces early mortality rates. CASE PRESENTATION: In this report, we present a case with microcirculatory failure of upper extremities as a rare symptom of hyperleukocytic AML M4 at initial presentation. CONCLUSIONS: Early diagnosis and treatment of patients with AML admitted to emergency services with these symptoms is too important to prevent from loss of extremities. Most of the complications of hyperleukocytosis can be reversible with early treatment.

Clinical features and prognostic factors of Magnusiomyces (Saprochaete) infections in haematology. A multicentre study of SEIFEM/Fungiscope.

BACKGROUND: Our multicentre study aims to identify baseline factors and provide guidance for therapeutic decisions regarding Magnusiomyces-associated infections, an emerging threat in patients with haematological malignancies. METHODS: HM patients with proven (Magnusiomyces capitatus) M. capitatus or (Magnusiomyces clavatus) M. clavatus (formerly Saprochaete capitata and Saprochaete clavata) infection diagnosed between January 2010 and December 2020 were recorded from the SEIFEM (Sorveglianza Epidemiologica Infezioni nelle Emopatie) group and FungiScope (Global Emerging Fungal Infection Registry). Cases of Magnusiomyces fungemia were compared with candidemia. RESULTS: Among 90 Magnusiomyces cases (60 [66%] M. capitatus and 30 (34%) M. clavatus), median age was 50 years (range 2-78), 46 patients (51%) were female and 67 (74%) had acute leukaemia. Thirty-six (40%) of Magnusiomyces-associated infections occurred during antifungal prophylaxis, mainly with posaconazole (n = 13, 36%) and echinocandins (n = 12, 34%). Instead, the candidemia rarely occurred during prophylaxis (p < .0001). First-line antifungal therapy with azoles, alone or in combination, was associated with improved response compared to other antifungals (p = .001). Overall day-30 mortality rate was 43%. Factors associated with higher mortality rates were septic shock (HR 2.696, 95% CI 1.396-5.204, p = .003), corticosteroid treatment longer than 14 days (HR 2.245, 95% CI 1.151-4.376, p = .018) and lack of neutrophil recovery (HR 3.997, 95% CI 2.102-7.601, p < .001). The latter was independently associated with poor outcome (HR 2.495, 95% CI 1.192-5.222, p = .015). CONCLUSIONS: Magnusiomyces-associated infections are often breakthrough infections. Effective treatment regimens of these infections remain to be determined, but neutrophil recovery appears to play an important role in the favourable outcome.

Modern management of iron overload in thalassemia major patients guided by MRI techniques: real-world data from a long-term cohort study.

Monitoring liver and cardiac iron stores by magnetic resonance imaging (MRI) enables identifying patients at risk of organ-specific morbidity and better tailoring of iron chelation therapy in thalassemia. Nevertheless, serum ferritin (SF) remains the only tool for monitoring iron status in most resource-poor regions. In this study, we assessed the impact of using MRI techniques to guide iron chelation therapy on iron overload outcomes in a cohort of 99 patients with thalassemia major (TM, mean age at baselines 20.7 ± 6.9 years) followed from 2006 to 2019. We also assessed the ability of SF trends to predict changes in consecutive liver iron concentration (LIC) and cardiac T2* (cT2*) measurements. The most commonly used chelator was deferasirox at baseline (65%) and final (72%) assessments. Overall, patients with safe LIC values (< 7 mg/g dw) increased from 57 to 77%, and safe cT2* values (> 20 ms) increased from 72 to 86%. We obtained the most significant improvement in patients with severe and moderate liver (p = 0.006 and p < 0.001) and cardiac (p < 0.0013 and p < 0.0001) iron overload at baseline. SF trends were in the same direction in 64% of changes in LIC, but only 42% of changes were proportional. Most of the changes in SF (64%) and LIC (61%) could not predict changes in cT2*. Moreover, downward trends in SF and LIC were associated with worsening cardiac iron in 29% and 23.5% of consecutive cT2* measurements. Liver and cardiac MRI-driven oral iron chelation improved the iron status of subjects with TM and demonstrated the importance of using validated MRI techniques in critical clinical decisions.

Assessment of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia: A Multicenter Study From Turkey.

Assestment of minimal residual disease (MRD) in childhood acute lymphoblastic leukemia (ALL) is of utmost importance both for risk classification and tailoring of the therapy. The data of pediatric ALL patients that received treatment with Berlin-Frankfurt-Münster (BFM) protocols were retrospectively collected from 5 university hospitals in Turkey. Of the 1388 patients enrolled in the study 390 were treated according to MRD-based protocols. MRD assestment was with real time quantitative polymerase chain reaction (qPCR) in 283 patients and with multiparametric flow cytometry (MFC)-MRD in 107 patients. MRD monitoring had upstaged a total of 8 patients (2%) from intermediate risk group to high-risk group. Univariate analysis revealed age 10 years or above, prednisone poor response, PCR-MRD ≥10-3 on day 33 and on day 78 as poor prognostic factors affecting event-free survival (EFS). Detection of >10% blasts on day 15 with MFC (MFC-high-risk group) was not shown to affect EFS and/or overall survival (log-rank P=0.339). Multiple logistic regression analysis revealed PCR-MRD ≥10-3 on day 78 as the only poor prognostic factor affecting EFS (odds ratio: 8.03; 95% confidence interval: 2.5-25; P=0.000). It is very important to establish the infrastructure and ensure necessary standardization for both MRD methods for optimal management of children with ALL.

Hepatitis-Associated Aplastic Anemia: Etiology, Clinical Characteristics and Outcome.

Hepatitis-associated aplastic anemia (HAA) is a form of acquired aplastic anemia (AA) in which bone marrow failure develops after an acute attack of hepatitis. Bone marrow failure leading to AA is generally severe in cases of HAA and fatal if left untreated. This retrospective multicenter study investigated clinical and laboratory characteristics, possible causes, treatment, and outcome of HAA in children. Twenty patients from 8 centers were included in the study. Aspartate aminotransferase and alanine aminotransferase were <3 to 5×upper limit of normal (ULN) in 2 patients, <5 to 10×ULN in 2 patients, and >10×ULN in 16 patients. Acute liver failure developed in 5 (29%) patients. Pancytopenia was simultaneously present in 6 of 20 (30%) patients. Eleven of the 20 patients (55%) were alive, in remission and transfusion free. Those who were alive either had undergone hematopoietic stem cell transplantation and/or immunosuppressive treatment, except 1 patient who had received no treatment. Patients with the diagnosis of acute hepatitis should be evaluated and followed up carefully for presence of cytopenia, so that definitive treatment of AA can be initiated in a timely and appropriate manner when needed.

Central Nervous System Fungal Infections in Children With Leukemia and Undergoing Hematopoietic Stem Cell Transplantation: A Retrospective Multicenter Study.

BACKGROUND: Central nervous system fungal infections (CNSFI) are seen in patients with hematologic malignancies and have high morbidity and mortality. Because of their rarity, there is limited data on CNSFI in children with no established treatment protocols or guidelines. MATERIALS AND METHODS: In this multicenter retrospective study, 51 pediatric patients with leukemia, 6 of whom had undergone bone marrow transplantation, with proven or probable CNSFI were evaluated. Fungal infections were defined as proven or probable based on European Organisation for Research and Treatment of Cancer criteria. Proven CNSFI was diagnosed by appropriate central nervous system (CNS) imaging or tissue sample findings in combination with positive microbiological results of cerebrospinal fluid. A positive culture, microscopic evidence of hyphae, a positive result of the galactomannan assays are defined as positive microbiological evidence. Probable CNSFI was defined as appropriate CNS imaging findings together with proven or probable invasive fungal infections at another focus without CNS when there is no other explanatory condition. Data was collected by using the questionnaire form (Supplemental Digital Content 1, http://links.lww.com/JPHO/A541 ). RESULTS: Seventeen patients had proven, 34 patients had probable CNSFI. Headaches and seizures were the most common clinical findings. The median time between the onset of fever and diagnosis was 5 days. The most common fungal agent identified was Aspergillus . Sixteen patients received single-agent, 35 received combination antifungal therapy. Surgery was performed in 23 patients. Twenty-two patients (43%) died, 29 of the CNSFI episodes recovered with a 20% neurological sequelae. CONCLUSION: CNSFIs should be considered in the differential diagnosis in patients with leukemia and refractory/recurrent fever, headache, neurologicalocular symptoms, and a radiologic-serological evaluation should be performed immediately. Early diagnosis and prompt management, both medical and surgical, are essential for improving clinical outcomes.

A Novel Homozygous TRNT1 Mutation in a Child With an Early Diagnosis of Common Variable Immunodeficiency Leading to Mild Hypogammaglobulinemia and Hemolytic Anemia.

Although sideroblastic anemias (SAs) may be associated with different etiologies, deterioration of mitochondrial heme biosynthesis in bone marrow erythroid cells is a general abnormality. Congenital SA associated with immunodeficiency, periodic fever, and developmental delay is because of loss-of-function mutations in the TRNT1 gene. We report a patient with a novel homozygous mutation in the TRNT1 gene presenting with anemia with siderocytes, hypogammaglobulinemia, hepatosplenomegaly, and brittle hair but without periodic fever or developmental delay. The patient was presented to emphasize the power of reverse phenotyping in the differential diagnosis of primary immunodeficiency patients with atypical features and to raise awareness for TRNT1 disease in case of coexistent SA and hypogammaglobulinemia.

Is Monitoring of Cytomegalovirus Disease Required in Nontransplant Pediatric Acute Lymphoblastic Leukemia?

INTRODUCTION: Cytomegalovirus (CMV) infections in developing countries are experienced at an early age. This study was performed to investigate the frequency of reactivation and risk factors of infection acquired at an early age of nontransplant acute lymphoblastic leukemia (ALL) patients receiving immunosuppressive therapy with weekly monitoring of CMV levels in Turkey. MATERIALS AND METHODS: This was a retrospective, single-center study of 172 pediatric patients (102 boys and 70 girls) with ALL. All patients were monitored routinely for CMV-DNA at the initial presentation of leukemia and twice a week during chemotherapy. The CMV immunoglobulin (Ig)M/IgG titers were measured at admission. RESULTS: CMV seropositivity at baseline was 90,11%. The overall prevalence of CMV infection (viremia) was 70.34%, 116 of whom were seropositive for CMV IgG and 5 of whom were negative for CMV at the time of ALL diagnosis. Reactivation was more common than de novo CMV infections (P=0.000). CMV seropositivity at the beginning of the leukemia diagnosis was found to be an independent predictor for developing CMV infection (P=0.001). A total of 60 CMV infection episodes were treated with antivirals. Four of these included organ involvement. The duration of CMV-DNA viremia episodes was longer in patients with CMV-DNA ≥1000 copies/mL (n=45) than in those with lower CMV-DNA levels (P=0.002). Infection was shown not to be associated with chemotherapy phase. CONCLUSION: This study suggests the importance of monitoring for CMV infections in developing countries because of frequent reactivations in seropositive ALL patients. It should be kept in mind that low CMV-DNA levels may also lead to organ involvement.

Management of a Patient With Congenital Biallelic CSF3R Mutation With GM-CSF.

Severe Congenital Neutropenia (SCN) is a rare inherited disease characterized by an absolute neutrophil count (ANC) lower than 500/µL. Genetic heterogeneity and biallelic CSF3R mutation has rarely been identified as an underlying genetic defect in SCN. The majority of SCN patients respond to granulocyte colony stimulating factor treatment; however, in patients with inherited CSF3R mutation, ANC cannot generally be increased with granulocyte colony stimulating factor treatment. In such cases, granulocyte macrophage colony stimulating factor presents as an effective treatment option. Herein, we report a case of a 5-year-old SCN girl with homozygous c610-611 del ins AG (p.Q204R) mutation in the CSF3R gene, who was successfully treated with granulocyte macrophage colony stimulating factor.

Coexistence of Gaucher Disease and severe congenital neutropenia.

Gaucher Disease (GD) is the most common lysosomal storage disorder has traditionally been classified into three clinical phenotypes. Type 3 GD is characterized by neurological involvement but neurological symptoms generally appear later in life than in type 2 disease. Neutropenia is much rarer than other hematological manifestations in GD and has not been scrutinized adequately. Severe congenital neutropenia (SCN) is a rare disease entity which is characterized by a paucity of peripherally circulating neutrophils with arrest of neutrophil maturation at the promyelocyte stage and consequent increased susceptibility to severe and recurrent infections. We report a patient who presented in the first year of life with visceral involvement and severe neutropenia in whom the propositus had a unique coexistence of Gaucher Disease and severe congenital neutropenia associated with a mutation in HAX1. In contrast to his expired siblings he had experienced no severe infections. These clinical observations suggest that enzyme replacement therapy may display a modulating factor with respect to the clinical course of SCN. SYNOPSIS: Our patient is the only report of the combination of Gaucher Disease and Kostmann Syndrome in the literature. The clinical course of our patient is not severe when comparing with exitus siblings and other Kostmann Syndrome patients. But when considering the patient's only clinical difference is ERT, this case is very important to emphasise the role of enzyme replacement therapy in bone marrow.

Homozygous c.130-131 ins A (pW44X) mutation in the HAX1 gene as the most common cause of congenital neutropenia in Turkey: Report from the Turkish Severe Congenital Neutropenia Registry.

BACKGROUND: Severe congenital neutropenia is a rare disease, and autosomal dominantly inherited ELANE mutation is the most frequently observed genetic defect in the registries from North America and Western Europe. However, in eastern countries where consanguineous marriages are common, autosomal recessive forms might be more frequent. METHOD: Two hundred and sixteen patients with severe congenital neutropenia from 28 different pediatric centers in Turkey were registered. RESULTS: The most frequently observed mutation was HAX1 mutation (n = 78, 36.1%). A heterozygous ELANE mutation was detected in 29 patients (13.4%) in our cohort. Biallelic mutations of G6PC3 (n = 9, 4.3%), CSF3R (n = 6, 2.9%), and JAGN1 (n = 2, 1%) were also observed. Granulocyte colony-stimulating factor treatment was given to 174 patients (80.6%). Two patients died with infectious complications, and five patients developed myelodysplastic syndrome/acute myeloblastic leukemia. The mean (± mean standard error) follow-up period was 129.7 ± 76.3 months, and overall survival was 96.8% (CI, 94.4-99.1%) at the age of 15 years. In Turkey, severe congenital neutropenia mostly resulted from the p W44X mutation in the HAX1 gene. CONCLUSION: In Turkey, mutation analysis should be started with HAX1, and if this is negative, ELANE and G6PC3 should be checked. Because of the very high percentage of consanguineous marriage, rare mutations should be tested in patients with a negative mutation screen.

Congenital Neutropenia Patient With Hypomorphic Biallelic CSF3R Mutation Responding to GCSF.

Congenital neutropenia (CN) is a rare disorder, and the most common gene responsible for CN is ELANE. Furthermore, the mutations of HAX1, G6PC3, and JAGN1 genes may cause CN. These patients generally find great benefit from subcutaneous administration of Granulocyte Colony Stimulating Factor (GCSF). In recent years, Biallelic Colony Stimulating Factor 3 Receptor (CSF3R) mutations have been described as an underlying defect of CN in several children. In contrast to the previous group, the patients who have a CSF3R mutation do not respond to GCSF treatment. Here, we present a CN patient with hypomorphic biallelic CSF3R mutation responding to GCSF.

Hepatosplenic Fungal Infections in Children With Leukemia-Risk Factors and Outcome: A Multicentric Study.

BACKGROUND: Invasive fungal infections, including hepatosplenic fungal infections (HSFI), cause significant morbidity and mortality in children with leukemia. There are not enough data to support for the best approach to diagnosis of HSFI in children, nor for the best treatment. PROCEDURE: In this multicentric study, we assessed the demographic data, clinical and radiologic features, treatment, and outcome of 40 children with leukemia and HSFI from 12 centers. RESULTS: All cases were radiologically diagnosed with abdominal ultrasound, which was performed at a median of 7 days, of the febrile neutropenic episode. Mucor was identified by histopathology in 1, and Candida was identified in blood cultures in 8 patients. Twenty-two had fungal infection in additional sites, mostly lungs. Nine patients died. Four received a single agent, and 36 a combination of antifungals. CONCLUSIONS: Early diagnosis of HSFI is challenging because signs and symptoms are usually nonspecific. In neutropenic children, persistent fever, back pain extending to the shoulder, widespread muscle pain, and increased serum galactomannan levels should alert clinicians. Abdominal imaging, particularly an abdominal ultrasound, which is easy to perform and available even in most resource-limited countries, should be recommended in children with prolonged neutropenic fever, even in the absence of localizing signs and symptoms.

HAX1 mutation positive children presenting with haemophagocytic lymphohistiocytosis.

The genetic basis of haemophagocytic lymphohistiocytosis (HLH) has not been elucidated in 10% of affected patients. In this study, we report four HLH episodes in three patients with HAX1 gene mutations. We screened the mutations associated with congenital neutropenia (CN) because the neutropenia persisted following HLH treatment. There were homozygous HAX1 mutations detected in all patients. This is the first case series of patients with CN caused by HAX1 mutation who presented with HLH. We hypothesize that severe neutropenia persists after an HLH episode in children without HLH mutations (especially infants) because these patients have CN caused by HAX1 mutations.