Hemophagocytic lymphohistiocytosis (HLH) is a rare and very dangerous condition characterized by abnormal activation of the immune system, causing hemophagocytosis, inflammation, and potentially widespread organ damage. The primary (genetic) form, caused by mutations affecting lymphocyte cytotoxicity, is most commonly seen in children. Secondary HLH is commonly associated with infections, malignancies, and rheumatologic disorders. Most current information on diagnosis and treatment is based on pediatric populations. HLH is a disease that should be diagnosed and treated promptly, otherwise it is fatal. Treatment is directed at treating the triggering disorder, along with symptomatic treatment with dexamethasone and etoposide. We present a 56-year-old patient who was admitted with worsening weakness, exertional dyspnea, dry and nonproductive cough, and a 5-pound weight loss associated with loss of appetite. This is among the rare disorders that are not commonly encountered in day-to-day practice. Our differential diagnoses were broad, including infection, such as visceral leishmaniasis, atypical/tuberculous mycobacteria, histoplasmosis, Ehrlichia, Bartonella, Brucella, Adenovirus, disseminated herpes simplex virus (HSV), hematological-like Langerhans cell histiocytosis, or multicentric Castleman disease; drug reaction, such as drug rash with eosinophilia and systemic symptoms (DRESS); and metabolic disorder, including Wolman's disease (infantile lysosomal acid lipase deficiency) or Gaucher's disease. Based on our investigations as described in our case report, it was narrowed down to hemophagocytic lymphohistiocytosis and COVID-19. Two COVID-19 tests were negative. His lab abnormalities and diagnostic testing revealed hemophagocytic lymphohistiocytosis. He was empirically started on antibiotics and dexamethasone, to be continued for 2 weeks then tapered if the patient showed continued improvement. Dexamethasone was tapered over 8 weeks. He improved on just one of the Food and Drug Administration (FDA)-approved medications, proving that treatment should be tailored to the patient. In addition, in this case study, we included the background, etiology, pathogenesis, diagnosis, management, and prognosis of HLH.
Subject(s)COVID-19 , Carcinoma, Neuroendocrine , Lymphohistiocytosis, Hemophagocytic , United States , Male , Child , Humans , Middle Aged , Lymphohistiocytosis, Hemophagocytic/complications , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , COVID-19/complications , Dexamethasone/therapeutic use
The case of a 57-year-old male patient with jaundice, high-grade fever, and upper abdominal pain who was recovering from a mild coronavirus disease-19 (COVID-19) infection is reported. Laboratory analysis showed liver injury with high levels of AST and ALT, as well as an elevated serum ferritin level. The patient underwent a bone marrow biopsy which showed features of hemophagocytic lymphohistiocytosis (HLH), a systemic syndrome caused by immune activation. The patient was successfully treated with etoposide and dexamethasone and kept on maintenance therapy with cyclosporine, with resolution of the HLH. The discussion highlights that COVID-19 infection may cause liver injury, and in severe cases, patients may develop HLH as a cause for liver injury. The incidence of HLH in adults with severe COVID-19 infection is estimated to be lower than 5%. The association between HLH and COVID-19 infection has been studied due to immunological hyperactivation. Signs such as persistent high fever, hepatosplenomegaly, and progressive pancytopenia should raise suspicion for the diagnosis of overlapping HLH. A specific approach using steroids and etoposide, followed by maintenance therapy with cyclosporine, is proposed in the HLH-94 protocol as the mainstay of treatment. It is suggested that HLH should be suspected in patients with laboratory signs of liver injury following COVID-19 infection, especially in patients with high-grade fever and a history of rheumatic conditions.
Subject(s)COVID-19 , Cyclosporins , Lymphohistiocytosis, Hemophagocytic , Male , Adult , Humans , Middle Aged , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , Lymphohistiocytosis, Hemophagocytic/etiology , COVID-19/complications , Etoposide/therapeutic use , Bone Marrow , Fever
The hyperinflammatory immune response in severe COVID-19 infection shares features with secondary hemophagocytic lymphohistiocytosis (sHLH) in the form of fever, cytopenia, elevated inflammatory markers, and high mortality. There are contrasting opinions regarding utility of HLH 2004 or HScore in the diagnosis of severe COVID-19-related hyperinflammatory syndrome (COVID-HIS). This was a retrospective study of 47 patients of severe COVID-19 infection, suspected to have COVID-HIS and 22 patients of sHLH to other illnesses, to evaluate the diagnostic utility and limitations of HLH 2004 and/or HScore in context to COVID-HIS and to also evaluate the utility of Temple criteria for predicting severity and outcome in COVID-HIS. Clinical findings, hematological, and biochemical parameters along with the predictor of mortality were compared between two groups. Only 6.4% (3/47) of cases fulfilled ≥5/8 HLH 2004 criteria and only 40.52% (19/47) of patients showed HScore >169 in COVID-HIS group. 65.9% (31/47) satisfied the Temple criteria in COVID-HIS as compared with 40.9% (9/22) in the non-COVID group (p = 0.04). Serum ferritin (p = 0.02), lactate dehydrogenase (p = 0.02), direct bilirubin (p = 0.02), and C-reactive protein (p = 0.03) were associated with mortality in COVID-HIS. Both HScore and HLH-2004 criteria perform poorly for identifying COVID-HIS. Presence of bone marrow hemophagocytosis may help to identify about one-third of COVID-HIS missed by the Temple Criteria.
Subject(s)COVID-19 , Lymphohistiocytosis, Hemophagocytic , Humans , Lymphohistiocytosis, Hemophagocytic/complications , Lymphohistiocytosis, Hemophagocytic/diagnosis , COVID-19/complications , Retrospective Studies , Syndrome , C-Reactive Protein
RATIONALE: Coronavirus disease (COVID-19), an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 virus, was reported in Wuhan of China in December 2019. The world is still in a state of pandemic owing to COVID-19. COVID-19 vaccines help our bodies develop immunity against the virus that causes COVID-19 without having to get the illness. Herein, we describe a rare case of a critical disorder, hemophagocytic lymphohistiocytosis (HLH), in a patient with nephritic sclerosis associated with hypertension, following mRNA COVID-19 vaccination. HLH is a life-threatening hyperinflammatory syndrome caused by aberrantly activated macrophages and cytotoxic T cells that may rapidly progress to terminal multiple organ failure. PATIENT CONCERNS: An 85-year-old Japanese woman with chronic renal failure and hypertension was included in this study. Routine laboratory investigations provided the following results: white blood cell (WBC) count, 4.6â ×â 109/L; hemoglobin (Hb), 8.1 g/dL; platelet count, 27â ×â 109/L; blood urea nitrogen 48.9 mg/dL, and serum creatinine 3.95 mg/dL. The patient developed malaise, vomiting, and persistent high fever (up to 39.7°C) on the 12th day after receiving the second dose of the vaccine. Initial evaluation revealed neutropenia. The total WBC count was 0.40â ×â 109/L (Neutrophils 0, Lymphocytes 240/µ, blast 0%); Hb 9.0 g/dL, platelet count 27â ×â 109/L; and, C Reactive Protein 9.64 mg/dL. DIAGNOSIS: Further tests showed hyperferritinemia (serum ferritin 2284.4 µg/L). Bone marrow examination revealed haemophagocytosis. A provisional diagnosis of HLH associated with the Comirnaty® vaccination was made based on the HLH-2004 diagnostic criteria. INTERVENTIONS: The patient was treated with granulocyte colony-stimulating factor and 500 mg methylprednisolone. OUTCOMES: A significant improvement was observed in the patient's condition; the abnormal laboratory results resolved gradually, and the patient was discharged. LESSONS: This case serves to create awareness among clinicians that HLH is a rare complication of COVID-19 vaccination and should be considered, especially in patients with a history of chronic renal failure and hypertension.
Subject(s)COVID-19 Vaccines , COVID-19 , Hypertension , Kidney Failure, Chronic , Lymphohistiocytosis, Hemophagocytic , Aged, 80 and over , Female , Humans , BNT162 Vaccine , COVID-19/complications , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Hypertension/complications , Kidney Failure, Chronic/complications , Lymphohistiocytosis, Hemophagocytic/chemically induced , Lymphohistiocytosis, Hemophagocytic/diagnosis , Vaccination/adverse effects
Subject(s)Antiprotozoal Agents , COVID-19 , Leishmaniasis, Visceral , Lymphohistiocytosis, Hemophagocytic , Humans , Leishmaniasis, Visceral/complications , Leishmaniasis, Visceral/diagnosis , Leishmaniasis, Visceral/drug therapy , Lymphohistiocytosis, Hemophagocytic/complications , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , COVID-19/complications , Antiprotozoal Agents/therapeutic use
Haemophagocytic lymphocytic histiocytosis (HLH) is a rare, life-threatening condition caused by abnormal activation of cytotoxic T lymphocytes, natural killer cells and macrophages resulting in hypercytokinaemia and immune-mediated injury of multiple organ systems. Secondary HLH occurs in the setting of a malignant, infectious or autoimmune stimulus. Macrophage activation syndrome (MAS) is the term used to describe HLH that develops secondary to rheumatological diseases such as lupus and juvenile idiopathic arthritis, among others. Commonly observed and documented symptoms include fever, organomegaly and lymphadenopathy. Given the potential for multiorgan failure in HLH/MAS, early identification, diagnosis and initiation of treatment is essential. We present a case of secondary HLH/MAS with acute inflammatory gastroenteritis in a middle-aged woman with a history of systemic lupus erythematosus.
Subject(s)Arthritis, Juvenile , Gastroenteritis , Lupus Erythematosus, Systemic , Lymphohistiocytosis, Hemophagocytic , Macrophage Activation Syndrome , Arthritis, Juvenile/complications , Female , Gastroenteritis/complications , Gastroenteritis/diagnosis , Humans , Lupus Erythematosus, Systemic/complications , Lymphohistiocytosis, Hemophagocytic/complications , Lymphohistiocytosis, Hemophagocytic/diagnosis , Macrophage Activation Syndrome/complications , Macrophage Activation Syndrome/etiology , Middle Aged
Subject(s)COVID-19/complications , Liver Failure, Acute/diagnosis , Liver Failure, Acute/etiology , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/etiology , Biomarkers , COVID-19/diagnosis , COVID-19/epidemiology , Cause of Death , Disease Susceptibility , Fatal Outcome , Female , Humans , Infant , Intensive Care Units, Pediatric , Liver Failure, Acute/epidemiology , Lymphohistiocytosis, Hemophagocytic/epidemiology , Symptom Assessment
Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with SARS-CoV-2 have cytokine storm. Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH that help in guiding its treatment. This study was the first to investigate serum sCD25 and sCD163 levels in SARS-CoV-2. Serum sCD25 and sCD163 were measured by ELISA in 29 patients with SARS-CoV-2, aged between 2 months and 16 years (13 had COVID-19 and 16 had multisystem inflammatory syndrome in children (MIS-C)), in comparison to 30 age- and sex-matched healthy control children and 10 patients with HLH. Levels of these markers were re-measured in 21 patients with SARS-CoV-2 who were followed up 3 months after recovery. Patients with SARS-CoV-2 had significantly higher serum sCD25 and sCD163 than healthy control children (P < 0.001). SARS-CoV-2 patients had significantly higher sCD25 than patients with HLH (P < 0.05). Serum sCD25 was a good differentiating marker between patients with SARS-CoV-2 and HLH. Although there was a significant decrease of serum sCD25 and sCD163 of the 21 SARS-CoV-2 patients who were followed up, these levels were still significantly higher than the healthy controls levels (P < 0.001). Conclusion: Serum sCD25 and sCD163 levels were up-regulated in SARS-CoV-2 patients. Serum sCD25 was a good differentiating marker between SARS-CoV-2 and HLH. This initial report requires further studies, on large scales, to investigate the relationship between SARS-CoV-2 and both sCD25 and sCD163, including the disease severity and outcome. The therapeutic role of sCD25 and sCD163 antagonists should also be studied in SARS-CoV-2 patients. What is Known: â¢ Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with COVID-19 have cytokine storm due to excessive pro-inflammatory host response. â¢ Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH. Monitoring of serum sCD25 and sCD163 levels can also help in guiding the treatment. What is New: â¢ Serum sCD25 and sCD163 levels are up-regulated in patients with COVID-19, including patients presenting with multisystem inflammatory syndrome in children (MIS-C). â¢ Serum sCD25 is a good differentiating marker between SARS-CoV-2 and HLH.
Subject(s)COVID-19 , Interleukin-2 Receptor alpha Subunit/blood , Lymphohistiocytosis, Hemophagocytic , Antigens, CD , Antigens, Differentiation, Myelomonocytic , Biomarkers , COVID-19/complications , COVID-19/diagnosis , Child , Cytokine Release Syndrome , Humans , Infant , Lymphohistiocytosis, Hemophagocytic/diagnosis , Receptors, Cell Surface , SARS-CoV-2 , Systemic Inflammatory Response Syndrome
CONTEXT.: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder of immune regulation that can eventually result in end-organ damage and death. HLH is characterized by uncontrolled activation of cytotoxic T lymphocytes, natural killer cells, and macrophages that can lead to a cytokine storm. The diagnosis of HLH is often challenging due to the diverse clinical manifestations and the presence of several diagnostic mimics. The prognosis is generally poor, warranting rapid diagnosis and aggressive management. OBJECTIVE.: To provide a comprehensive review of the pathogenesis, clinical features, diagnosis, and management of HLH. DATA SOURCES.: Peer-reviewed literature. CONCLUSIONS.: HLH is a condition where a complete understanding of the pathogenesis, early diagnosis, and proper management has an important role in determining patient outcome. Genetic mutations causing impairment in the function of cytotoxic T lymphocytes and natural killer cells have been identified as the root cause of familial HLH; however, the specific pathogenesis of acquired HLH is unclear. The HLH-2004 protocol used in the diagnosis of HLH was originally developed for the pediatric population. The HLH-2004 protocol still forms the basis of the diagnosis of HLH in adults, although its use in adults has not been formally validated yet. Treatment of HLH is primarily based on the HLH-94 protocol, which involves suppressing the inflammatory response, but the treatment needs to be modified in adults depending on the underlying cause and comorbidities.
Subject(s)Lymphohistiocytosis, Hemophagocytic , Child , Humans , Killer Cells, Natural , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/genetics , Lymphohistiocytosis, Hemophagocytic/therapy , Macrophages
BACKGROUND: Multisystem inflammatory syndrome in children (MIS-C) is a potentially life-threatening sequela of severe acute respiratory syndrome coronavirus 2 infection characterized by hyperinflammation and multiorgan dysfunction. Although hyperinflammation is a prominent manifestation of MIS-C, there is limited understanding of how the inflammatory state of MIS-C differs from that of well-characterized hyperinflammatory syndromes such as hemophagocytic lymphohistiocytosis (HLH). OBJECTIVES: We sought to compare the qualitative and quantitative inflammatory profile differences between patients with MIS-C, coronavirus disease 2019, and HLH. METHODS: Clinical data abstraction from patient charts, T-cell immunophenotyping, and multiplex cytokine and chemokine profiling were performed for patients with MIS-C, patients with coronavirus disease 2019, and patients with HLH. RESULTS: We found that both patients with MIS-C and patients with HLH showed robust T-cell activation, markers of senescence, and exhaustion along with elevated TH1 and proinflammatory cytokines such as IFN-Î³, C-X-C motif chemokine ligand 9, and C-X-C motif chemokine ligand 10. In comparison, the amplitude of T-cell activation and the levels of cytokines/chemokines were higher in patients with HLH when compared with patients with MIS-C. Distinguishing inflammatory features of MIS-C included elevation in TH2 inflammatory cytokines such as IL-4 and IL-13 and cytokine mediators of angiogenesis, vascular injury, and tissue repair such as vascular endothelial growth factor A and platelet-derived growth factor. Immune activation and hypercytokinemia in MIS-C resolved at follow-up. In addition, when these immune parameters were correlated with clinical parameters, CD8+ T-cell activation correlated with cardiac dysfunction parameters such as B-type natriuretic peptide and troponin and inversely correlated with platelet count. CONCLUSIONS: Overall, this study characterizes unique and overlapping immunologic features that help to define the hyperinflammation associated with MIS-C versus HLH.
Subject(s)COVID-19 , Lymphohistiocytosis, Hemophagocytic , COVID-19/complications , Child , Cytokines/metabolism , Humans , Ligands , Lymphohistiocytosis, Hemophagocytic/diagnosis , Systemic Inflammatory Response Syndrome , Vascular Endothelial Growth Factor A
Haemophagocytic lymphohistiocytosis (HLH) is one of the rare haematological syndromes more commonly reported in infants/children than adults. This disease is known for its aggressive dysregulated immune response affecting the host rapidly, causing multiorgan dysfunction and thus carries a high mortality. The disease still remains cryptic in this current decade despite all the developments in the ever-evolving field of haematology. Due to its rare occurrence and being more frequent in infants and the paediatric population, the literature lacks enough data to standardise therapies. Such events in adults and the elderly are invariably related to an underlying insult such as infections, other autoimmune or rheumatological diseases or drugs. We describe an interesting case of a middle-aged Caucasian woman who presented with fever, pancytopenia and hepatitis, who was eventually diagnosed with HLH just in time to receive the life-saving specific treatment as per available guidelines.
Subject(s)Arthritis, Rheumatoid , Lymphohistiocytosis, Hemophagocytic , Adult , Aged , Anticonvulsants/therapeutic use , Arthritis, Rheumatoid/complications , Arthritis, Rheumatoid/drug therapy , Child , Female , Fever/complications , Humans , Lamotrigine/therapeutic use , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , Lymphohistiocytosis, Hemophagocytic/etiology , Middle Aged
BACKGROUND AND OBJECTIVES: To compare previous hemophagocytic lymphohistiocytosis criteria with adult coronavirus disease 2019 (COVID-19)-associated hyperinflammatory syndrome (cHIS) criteria for the diagnosis of hyperinflammation in pediatric patients with COVID-19. The secondary objective was to assess treatment response to intravenous (IV) anakinra in these patients. METHODS: This case series included children admitted to the PICU for COVID-19 pneumonia with hyperinflammation and treated with IV anakinra between July 2020 to April 2021. Hyperinflammatory criteria were determined for each patient. Clinical course, chest imaging, and inflammatory marker trends were assessed pre- and post-anakinra treatment. RESULTS: All patients had a cHIS criteria score of ≥5. Two patients met 2004-hemophagocytic lymphohistiocytosis criteria. Only the patient that required extracorporeal membrane oxygenation met the H-Score cut-off value. All but one patient had a decrease in their inflammatory markers and improvement in clinical status with early initiation of adjunctive IV anakinra. CONCLUSIONS: In this case series, adult cHIS criteria were successfully used to identify pediatric COVID-19 patients with hyperinflammation. Ferritin levels decreased after the early initiation of IV anakinra.
Subject(s)COVID-19 , Lymphohistiocytosis, Hemophagocytic , Pneumonia , Adult , COVID-19/complications , Child , Humans , Interleukin 1 Receptor Antagonist Protein/therapeutic use , Lymphohistiocytosis, Hemophagocytic/complications , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , Pneumonia/drug therapy , Systemic Inflammatory Response Syndrome
PURPOSE: The coronavirus disease 2019 (COVID-19) pandemic has led to the approval of novel vaccines with different mechanisms of action. Until now, more than 4.7 billion persons have been vaccinated around the world, and adverse effects not observed in pre-authorization trials are being reported at low frequency. METHODS: We report a case of severe hemophagocytic lymphohistiocytosis (HLH) after SARS-CoV-2 immunization and performed a literature search for all reported cases of COVID-19 vaccine-associated HLH. RESULTS: A 24-year-old female developed HLH after immunization with the mRNA COVID-19 vaccine Comirnaty. Diagnosis was made according to HLH-2004 criteria; the HScore was 259 (> 99% HLH probability) with maximum ferritin of 138.244 µg/L. The patient was initially treated with intravenous immunoglobulins (IVIGs) and dexamethasone without response. The addition of the human interleukin 1 receptor antagonist Anakinra resulted in full recovery within 6 weeks after vaccination. A literature search revealed 15 additional cases of HLH after SARS-CoV-2 vaccination, the majority after immunization with Comirnaty (n = 7) or the viral vector vaccine Vaxzevria (n = 6). Treatment modalities included corticosteroids (n = 13), Anakinra (n = 5), IVIGs (n = 5), and etoposide (n = 2). Eight patients underwent combination treatment. Three of 16 patients died. CONCLUSION: COVID-19 vaccines may occasionally trigger HLH, and Anakinra may be an efficacious treatment option for this condition.
Subject(s)COVID-19 Vaccines , COVID-19 , Lymphohistiocytosis, Hemophagocytic , Adrenal Cortex Hormones , Adult , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Dexamethasone/therapeutic use , Etoposide , Female , Ferritins , Humans , Immunoglobulins, Intravenous , Interleukin 1 Receptor Antagonist Protein , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/drug therapy , Lymphohistiocytosis, Hemophagocytic/etiology , RNA, Messenger , Receptors, Interleukin-1 , SARS-CoV-2 , Vaccination , Young Adult
Cytokine storm is an umbrella term that describes an inflammatory syndrome characterized by elevated levels of circulating cytokines and hyperactivation of innate and/or adaptive immune cells. One type of cytokine storm is hemophagocytic lymphohistiocytosis (HLH), which can be either primary or secondary. Severe COVID-19-associated pneumonia and acute respiratory distress syndrome (ARDS) can also lead to cytokine storm/cytokine release syndrome (CS/CRS) and, more rarely, meet criteria for the diagnosis of secondary HLH. Here, we review the immunobiology of primary and secondary HLH and examine whether COVID-19-associated CS/CRS can be discriminated from non-COVID-19 secondary HLH. Finally, we review differences in immunobiology between these different entities, which may inform both clinical diagnosis and treatment of patients.
Subject(s)COVID-19/complications , Cytokine Release Syndrome/etiology , Cytokine Release Syndrome/therapy , Lymphohistiocytosis, Hemophagocytic/diagnosis , Lymphohistiocytosis, Hemophagocytic/etiology , Antibodies, Monoclonal/therapeutic use , Antibodies, Neutralizing/therapeutic use , Cytokine Release Syndrome/virology , Humans , Interleukin 1 Receptor Antagonist Protein/therapeutic use , Lymphohistiocytosis, Hemophagocytic/immunology , Lymphohistiocytosis, Hemophagocytic/therapy
BACKGROUND: Based on the information obtained so far, COVID- 19 is relatively mild in children. We will present a 6-month-old male patient infected with COVID -19 in April 2020, while receiving HLH 2004 chemotherapy protocol with the diagnosis of familial (Genetic / Primary) Hemophagocytic Lymphohistiocytosis (HLH). CASE: Herein we present a case accompanied by a defective perforin gene defect in the primary HLH pathogenesis, Covid-19 infection with the presence of fever and hyperferritinemia, which was evaluated in favor of reactivation and the patient was given both the HLH-2004 chemotherapy protocol treatment and COVID -19 therapy as recommended by the guidelines. Our patient improved clinically and in terms of laboratory test results at the end of the 15 < sup > th < /sup > day of hospitalization and was discharged. CONCLUSIONS: It should be remembered that COVID-19 can be seen with different clinical manifestations in the pediatric age group, and COVID-19 tests should be recommended, especially in children with immunosuppression and fever.