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

Clinical Characteristics and Treatment of Familial Hemophagocytic Lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (fHLH) comprises a group of autosomal recessive disorders characterized by germline loss-of-function variants that negatively impact lymphocyte cytotoxicity. These disorders exhibit variable clinical presentations, most often in association with severe hyperinflammation. fHLH is diagnosed through clinical and laboratory assessments as well as genetic testing and immunologic assays. In the absence of therapy to control the hyperactive immune system, fHLH is generally fatal. Treatment has historically taken the form of cytotoxic chemotherapy and/or immunosuppressive therapy, although targeted inhibitors of inflammatory cytokines and their downstream signaling are increasingly being utilized. Definitive treatment requires allogeneic hematopoietic cell transplantation.

Efficacy of T-cell assays for the diagnosis of primary defects in cytotoxic lymphocyte exocytosis

ABSTRACT

Primary hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disorder associated with autosomal recessive variants in genes required for perforin-mediated lymphocyte cytotoxicity. A rapid diagnosis is crucial for successful treatment. Although defective cytotoxic T lymphocyte (CTL) function causes pathogenesis, quantification of natural killer (NK)-cell exocytosis triggered by K562 target cells currently represents a standard diagnostic procedure for primary HLH. We have prospectively evaluated different lymphocyte exocytosis assays in 213 patients referred for evaluation for suspected HLH and related hyperinflammatory syndromes. A total of 138 patients received a molecular diagnosis consistent with primary HLH. Assessment of Fc receptor-triggered NK-cell and T-cell receptor (TCR)-triggered CTL exocytosis displayed higher sensitivity and improved specificity for the diagnosis of primary HLH than routine K562 cell-based assays, with these assays combined providing a sensitivity of 100% and specificity of 98.3%. By comparison, NK-cell exocytosis after K562 target cell stimulation displayed a higher interindividual variability, in part explained by differences in NK-cell differentiation or large functional reductions after shipment. We thus recommend combined analysis of TCR-triggered CTL and Fc receptor-triggered NK-cell exocytosis for the diagnosis of patients with suspected familial HLH or atypical manifestations of congenital defects in lymphocyte exocytosis.

Outcome and Prognostic Factors of Hemophagocytic Lymphohistiocytosis in Children: Experience From a Low- and Middle-Income Country

Objective Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition especially in low- and middle-income countries (LMICs). This study was done to evaluate the outcome and prognostic factors of HLH in patients presenting to our center. Methods The study was carried out at the Paediatric Oncology Department of Combined Military Hospital (CMH) in Rawalpindi, Pakistan. All cases of HLH, from one month to 15 years of age enrolled between January 1, 2013 to June 30, 2023, were included. IBM SPSS Statistics for Windows, version 25.0 (released 2017, IBM Corp., Armonk, NY) was used for statistical analysis, and t-test and chi-square tests were used for comparison between continuous and categorical variables. Frequencies and percentages were calculated for categorical variables. Results Out of 115 patients, seven (6%) abandoned the treatment. The data of 108 cases, including 58 males (53.7%), were analyzed. The mean age at diagnosis was 31.5 ± 39.03 months. The mean time to reach a pediatric oncologist was 30.20 ± 22.15 days. Fever and pallor were common symptoms occurring in 107 (99.1%) and 98 (90.7%) cases, respectively. Jaundice was present in 44 (40.7%), visceromegaly in 64 (59.3%), and bruising/bleeding in 16 cases (14.8%). Twenty-six (24.1%) patients underwent hematopoietic stem cell transplant (HSCT), out of which 17 (65.4%) children were cured. Overall survival at two years, five years, and 10 years was 38%, 37%, and 36.1%, respectively. Disease-free survival at two years, five years, and 10 years was 33.3%, 32.4%, and 31.5%, respectively. Conclusion HLH leads to high mortality due to delayed or misdiagnosis in LMICs. Early diagnosis and early referral to a pediatric oncologist is the detrimental factor in survival for HLH. HSCT is the treatment of choice for primary, refractory, or relapse cases.

An Unusual Complication of Measles Infection in a Pediatric Patient: A Case Report of Measles-Induced Hemophagocytic Lymphohistiocytosis (HLH) From Jordan

Measles is a highly contagious infection that leads to many serious complications. Despite the significant global effort to eradicate it, it still represents a major threat due to suboptimal vaccination coverage, especially after the coronavirus disease 2019 (COVID-19) pandemic that affected all routine childhood vaccinations. One of its fatal complications, which has been reported a few times in the literature, is hemophagocytic lymphohistiocytosis (HLH). We discuss a case of a 14-month-old unvaccinated female patient who developed measles-induced HLH and was treated with intravenous immunoglobulins (IVIG) and steroids; unfortunately, she developed multiorgan failure and passed away before chemotherapy could be initiated.