Hemophagocytic Lymphohistiocytosis in Children

Dengue-Associated Hemophagocytic Lymphohistiocytosis: A Narrative Review of Its Identification and Treatment

Dengue's lack of specific treatments beyond supportive care prompts a focus on uncovering additional pathophysiological factors. Dengue-associated hemophagocytic lymphohistiocytosis (HLH), characterized by dysregulated macrophage activation and cytokine storm, remains underexplored despite its potential to worsen disease severity and mortality. While rare, dengue-associated HLH disproportionately affects severe cases, significantly impacting mortality rates. To mitigate high mortality, early identification and familiarity with dengue-associated HLH are imperative for prompt treatment by clinicians. This narrative review therefore aims to examine the current clinical and therapeutic knowledge on dengue-associated HLH, and act as a resource for clinicians to improve their management of HLH associated with severe dengue. Dengue-associated HLH should be considered for all cases of severe dengue and may be suspected based on the presence of prolonged or recurrent fever for >7 days, or anemia without intravascular hemolysis or massive bleeding. Diagnosis relies on fulfilling at least five of the eight HLH-2004 criteria. Treatment predominantly involves short courses (3-4 days) of high-dose steroids (e.g., dexamethasone 10 mg/m2), with additional therapies considered in more severe presentations. Notably, outcomes can be favorable with steroid therapy alone.

Secondary hemophagocytic lymphohistiocytosis in children (Review)

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening condition characterized by hyperinflammation in an uncontrolled and ineffective immune response. Despite great improvement in diagnosis and treatment, it still represents a challenge in clinical management, with poor prognosis in the absence of an aggressive therapeutic approach. The present literature review focuses on secondary HLH at pediatric age, which represents a heterogeneous group in terms of etiology and therapeutic approach. It summarizes the most recent evidence on epidemiology, pathophysiology, diagnosis, treatment and prognosis, and provides a detailed description and comparison of the major subtypes of secondary HLH. Finally, it addresses the open questions with a focus on diagnosis and new treatment insights.

Presentations and outcomes of familial hemophagocytic lymphohistiocytosis in the pediatric intensive care units (PICUs)

Objectives

We aimed to describe Familial Hemophagocytic Lymphohistiocytosis (F-HLH) patients' clinical features, intensive care courses, and outcomes.

Methods

Multi-center retrospective cohort study of pediatric patients diagnosed with F-HLH from 2015 to 2020 in five tertiary centers in Saudi Arabia. Patients were classified as F-HLH based on their genetic confirmation of known mutation or on their clinical criteria, which include a constellation of abnormalities, early disease onset, recurrent HLH in the absence of other causes, or a family history of HLH.

Results

Fifty-eight patients (28 male, 30 female), with a mean age of 21.0 ± 33.9 months, were included. The most common principal diagnosis was hematological or immune dysfunction (39.7%), followed by cardiovascular dysfunction in 13 (22.4%) patients. Fever was the most common clinical presentation in 27.6%, followed by convulsions (13.8%) and bleeding (13.8%). There were 20 patients (34.5%) who had splenomegaly, and more than 70% of patients had hyperferritinemia >500 mg/dl, hypertriglyceridemia >150 mg/dl and hemophagocytosis in bone marrow biopsy. Compared to deceased patients 18 (31%), survivors had significantly lower PT (p = 041), bilirubin level of <34.2 mmol/L (p = 0.042), higher serum triglyceride level (p = 0.036), and lesser bleeding within the initial 6 h of admission (p = 0.004). Risk factors for mortality included requirements of higher levels of hemodynamic (61.1% vs. 17.5%, p = 0.001) and respiratory (88.9% vs. 37.5%, p < 0.001) support, and positive fungal cultures (p = 0.046).

Conclusions

Familial HLH still represents a challenge in the pediatric critical care setting. Earlier diagnosis and prompt initiation of appropriate treatment could improve F-HLH survival.

Pediatric hemophagocytic lymphohistiocytosis in a tropical country: Results of a multicenter study in Thailand

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening condition caused by genetic mutation or various triggers disturbing the immune system.

METHODS

A multicenter retrospective study of pediatric patients with HLH receiving a diagnosis between January 2005 and December 2019 from three pediatric oncology centers was conducted to explore the clinical characteristics and determine prognostic factors associated with outcomes among Thai children.

RESULTS

In all, 78 patients with HLH with a median age at diagnosis of 3.17 (range, .08-17.83) years were enrolled. The male to female ratio was 1.2:1. The most common type of HLH was infection-associated hemophagocytic syndrome (IAHS) (n = 59, 75%) of which Epstein-Barr virus was the most common pathogen. Thrombocytopenia, hyperbilirubinemia, and treatment response at weeks 2 and 8 after initiating treatment were associated with mortality. Platelet count <50,000 cells/mm³ was the only independent prognostic factor to define survival outcome (p-value .035). Two-year overall survival rate was 71.3% (95% confidence interval, 59.2%-80.3%). Survival rates between IAHS, malignant associated HLH, macrophage activation syndrome, and unspecific HLH did not significantly differ (p-value .571).

CONCLUSION

IAHS was the most common cause among pediatric HLH in Thailand. The outcomes of Thai children with HLH were comparable to those of developed countries. Platelet count <50,000 cells/mm³ was the only independent prognostic factor to define survival outcome.

Outcome of Viral-associated Hemophagocytic Lymphohistiocytosis at a Tertiary Hospital

BACKGROUND

Little is known about viral-associated hemophagocytic lymphohistiocytosis (HLH) in Oman. This study was done to assess the epidemiology, clinical features and outcome of viral-associated HLH in our setting.

METHODS

We retrospectively reviewed children (0-18 years) managed for viral-associated HLH at the Sultan Qaboos University Hospital, Oman, over a 15-year period (2006-2020). Patients' medical records were used to describe their demographic, clinical and laboratory features, management and outcome.

RESULTS

Fifty-six children were managed for HLH at Sultan Qaboos University Hospital over the last 15 years (2006-2020) of whom a third (19; 34%) had a viral trigger. The median age at the time of diagnosis of viral-associated HLH was 83 (13-96) months. Fever, cytopenia, hyperferritinemia and evidence of hemophagocytosis in bone marrow were the most consistent findings. Most of these children had either genetic predisposition to HLH (8/19; 42%) or underlying immunodeficiency secondary to malignant conditions or chemotherapy/hematopoietic stem cell transplantation (6/19; 32%). Epstein-Barr virus (9; 47%) followed by cytomegalovirus (6; 31%) was the most common viral trigger in our setting. Treatment included antivirals (8; 42%), HLH 2004 protocol (4; 21%), rituximab (4; 21%) and hematopoietic stem cell transplantation (3; 16%). Fourteen children (74%) had full recovery.

CONCLUSIONS

In our small cohort, viral-associated HLH was more frequently encountered in children with genetic predisposition to HLH or children with underlying immunodeficiency. In addition, we found that the outcome is overall good for children who have no genetic predisposition to HLH and children with genetic predisposition who underwent hematopoietic stem cell transplantation.

Clinical Features and Prognostic Factors of Early Outcome in Pediatric Hemophagocytic Lymphohistiocytosis: A Retrospective Analysis of 227 Cases

Hemophagocytic lymphohistiocytosis (HLH) is a rare but life-threatening clinical syndrome in children, and the knowledge of it is still limited. Two hundred twenty-seven children with HLH in our hospital were retrospectively analyzed from January 2001 to December 2018. The age of the patients on admission ranged from 1 day to 14 years old. The 3 most common clinical manifestations include fever (98.7%), hepatomegaly (95.6%), and splenomegaly (92.1%). The decrease of high-density lipoprotein cholesterol (99.1%) is very common in children with HLH. Albumin<25 g/L, activated partial thromboplastin time >65 s, and lactose dehydrogenase >1000 U/L were independent risk factors for poor early prognosis in children with HLH, and their odds ratio values were 2.515, 3.094, and 2.378, respectively, while age >28 months was identified as a protective factor (odds ratio=0.295). Of the 227 children, 67 (29.52%) died within 30 days of onset. The mortality rate in 2013 to 2018 was significantly lower than that in 2001 to 2012 (16.35% vs. 40.65%, P=0.000). The shortening of the time from onset to admission and the reduction of time from admission to definite diagnosis could be some of the reasons for the decrease of HLH mortality in 2013 to 2018 (P<0.05, respectively). Our study suggests that early identification of risk factors for HLH, timely diagnosis and treatment are important measures to improve the short-term prognosis of HLH in children.

Macrophage Activation Syndrome in Children: Diagnosis and Management

Macrophage activation syndrome is a severe yet under-recognized complication encountered in pediatric rheumatology. It manifests as secondary hemophagocytic lymphohistiocytosis leading to a hyper-inflammatory state resulting from an underlying cytokine storm. If unchecked, it may lead to multiorgan failure and mortality. Early diagnosis and timely initiation of specific therapy is pivotal for a successful outcome. This review outlines the key clinical and laboratory features and management of macrophage activation syndrome.

Haemophagocytic lymphohistiocytosis secondary to brucellosis in a young child

Brucellosis is a common zoonotic disease worldwide. It has protean clinical manifestation and sometimes may has a life-threatening complication. A 4-year-old boy presented with a history of fever, myalgia and appetite loss for 3 weeks. On examination, he had hepatosplenomegaly. The initial working diagnosis was an infection, autoimmune disease and malignancy. Investigations showed positive Brucella serology, and he was started on rifampicin and cotrimoxazole. He was further investigated because of persistent fever, which revealed evidence of haemophagocytic lymphohistiocytosis (HLH). He continued treatment for brucellosis, except rifampicin which was replaced with doxycyclin due to a worsening liver function. The child showed complete clinical and biochemical improvement after 6 weeks of therapy. HLH is a life-threatening condition and should be suspected in children with brucellosis, who did not respond to appropriate antibiotics treatment. Secondary HLH does not always require specific therapy; it may improve with adequate treatment of the underlying condition.

Thrombotic microangiopathy led to acute kidney injury in an infant with hemophagocytic lymphohistiocytosis: A case report

Hemophagocytic lymphohistiocytosis (HLH) is a rare but fatal clinical syndrome frequently complicated by acute kidney injury (AKI) and acute tubular necrosis. Renal thrombotic microangiopathy (TMA) is a specific pathological feature of childhood HLH and few cases have been reported among infants. The present study presents a rare case of HLH with TMA in an infant. A 15-month-old infant with a week-long history of fever was admitted to hospital. The infant presented with AKI and subsequently a reduction in platelet and hemoglobin levels. TMA was diagnosed by kidney biopsy and the clinical, laboratory and bone marrow biopsy findings met the criteria of HLH. Due to a progressive increase in serum creatinine levels, hemodialysis was initiated on the second day following admission. Dexamethasone was administered to treat both the fever and HLH. The patient's body temperature returned to a normal range and platelet and hemoglobin levels were stable after 14 days of admission. Renal function stabilized on day 21. The results of genetic testing did not identify any disease-related variations. Childhood HLH is a severe condition and mortality can be reduced by early diagnosis and correct treatment. For patients with HLH and AKI, the possible role of TMA should be considered. Renal biopsy can help to identify the cause of AKI and can be performed when the patient's condition is stable.

Hemophagocytic Lymphohistiocytosis in a PICU of a Developing Economy: Clinical Profile, Intensive Care Needs, Outcome, and Predictors of Mortality

OBJECTIVES

To describe the clinical profile, intensive care needs, outcome, and predictors of mortality in critically ill children with hemophagocytic lymphohistiocytosis.

DESIGN

Retrospective case series.

SETTING

PICU of a tertiary care teaching hospital in North India.

PATIENTS

Children 2 months to 12 years old with the diagnosis of hemophagocytic lymphohistiocytosis admitted to PICU from January 2012 to April 2019 (7¼ yr).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-two children with hemophagocytic lymphohistiocytosis (60 secondary and two primary) were enrolled. The median (interquartile range) age of the study group was 82 months (50.5-124 mo). The median (interquartile range) Pediatric Risk of Mortality III score was 16 (10-23). Majority of hemophagocytic lymphohistiocytosis was infection-associated (n = 51; 82.3%). Among these, scrub typhus accounted for 29% of cases (n = 18), dengue 17.7% (n = 11), bacterial sepsis 14.5% (n = 9), enteric fever 6.5% (n = 4), and other infections 14.5% (n = 9). Systemic-onset juvenile idiopathic arthritis accounted for 9.7% of cases (n = 6) and malignancy for 4.8% patients (n = 3). Majority of cases were treated with steroids (77.4%) and IV immunoglobulin (25.8%). Various complications noted were shock (71%), acute kidney injury (66.1%), acute respiratory distress syndrome (41.9%), disseminated intravascular coagulation (54.8%), CNS dysfunction (54.8%), multiple organ dysfunction syndrome (82.3%), and healthcare-associated infections (14.5%). Intensive care needs for primary illness and/or hemophagocytic lymphohistiocytosis included mechanical ventilation (74.2%); packed RBC (72.3%), fresh frozen plasma (40.3%), and platelet (48.4%) transfusion; vasoactive drugs (71%); and renal replacement therapy (24.2%). The median duration of PICU stay was 5 days (2.5-9.5 d) and mortality was 59.7% (n = 37). On univariate analysis, nonsurvivors had higher Pediatric Risk of Mortality III score; higher proportion of shock, acute kidney injury, acute respiratory distress syndrome, disseminated intravascular coagulation, and multiple organ dysfunction syndrome; the need for blood and blood components, mechanical ventilation, vasoactive drugs, and renal replacement therapy; higher Vasoactive-Inotropic Score; and prolonged duration of mechanical ventilation compared with survivors.

CONCLUSIONS

Hemophagocytic lymphohistiocytosis in PICU is commonly secondary to tropical infections and associated with high mortality. Higher severity of illness; shock and multiple organ dysfunction syndrome; need for blood and blood products, mechanical ventilation, vasoactive drugs, and renal replacement therapy; higher Vasoactive-Inotropic Score; and prolonged mechanical ventilation predicted death. Treatment of underlying infection and a less intense immunosuppressive therapy (steroids ± IV immunoglobulin) are suggested options. A high index of suspicion for complicating hemophagocytic lymphohistiocytosis is required in children with prolonged fever, cytopenias, organomegaly, and organ dysfunction not responding to conventional treatment.