Hyperferritinemia in reactive hemophagocytic syndrome report of four adult cases

Lymphoma-associated hemophagocytic lymphohistiocytosis (LA-HLH): a scoping review unveils clinical and diagnostic patterns of a lymphoma subgroup with poor prognosis

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome driven by pathologic activation of cytotoxic T-lymphocytes and macrophages. Despite advances in diagnostics and management, adult patients with lymphoma-associated HLH (LA-HLH) harbor particularly poor prognosis and optimal treatment remains challenging. As systematic data on LA-HLH are scarce, we aimed to synthesize research evidence by thorough analysis of the published literature in PubMed (MEDLINE-database) within the context of a scoping review. Of 595 search results, 132 articles providing information on 542 patients were reviewed and analyzed. Median patient age was 60 years (range, 18-98) with male predominance (62.7%). B- and T-NHL were equally represented (45.6% and 45.2%), Hodgkin's lymphoma was reported in 8.9% of the cases. The majority of patients (91.6%) presented in Ann-Arbor-Stages III and IV, and bone marrow infiltration was observed in a significant proportion of patients (61.5%). Soluble CD25 levels were markedly elevated (median 10,000 U/ml), with levels beyond 10,000 U/ml indicating unfavorable prognosis for 30-day and overall survival. 66.8% of the patients died after median 5.1 months. LA-HLH remains a clinical challenge requiring specialized management. Timely diagnosis and appropriate lymphoma-specific treatment are of utmost importance to enhance patient outcomes.

Tuberculosis-Associated Hemophagocytic Lymphohistiocytosis: A Review of Current Literature

Hemophagocytic lymphohistiocytosis (HLH) is a condition of immune dysregulation and hyperinflammation, leading to organ failure and death. Malignancy, autoimmune conditions, and infections, including Mycobacterium tuberculosis (TB), are all considered triggers of HLH. The aim of this study was to review all reported cases of TB-associated HLH in English literature, and to summarize the epidemiology, diagnostics, treatment, and mortality in patients with concomitant HLH and TB. A systematic review of described cases with TB-associated HLH, via a structured literature search in the medical database PubMed, is presented. Additional articles were included through cross-referencing with existing review articles. Articles were reviewed based on a predetermined set of criteria. A total of 116 patients with TB-associated HLH were identified with a male:female ratio of about 3:2. The age at presentation ranged from 12 days to 83 years. Malignancy, autoimmunity, and renal failure were the most common comorbid conditions. Most patients received both tuberculostatic and specific immunomodulating treatment, which was associated with a 66% (48/73) survival rate compared to 56% (15/27) in those receiving only tuberculostatic treatment, and 0% (0/13) in those receiving only immunomodulating treatment. The survival rate was 55% overall. The overlapping presentation between disseminated TB and HLH poses challenging diagnostics and may delay diagnosis and treatment, leading to increased mortality. TB should be considered as a potential trigger of HLH; clinicians' knowledge and awareness of this may result in the appropriate investigations needed to ensure diagnosis and proper treatment.

Clinical, immunological and genetic findings in patients with UNC13D deficiency (FHL3): A systematic review

BACKGROUND

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare autosomal recessive immune disorder that is caused by mutations in 6 different genes related to the formation and function of secretory lysosomes within cytotoxic T lymphocytes and natural killer (NK) cells. Thus, defect in these genes is associated with the accumulation of antigens due to defective cytotoxic function. FHL type 3 (FHL3) accounts for nearly 30-40% of FHL, and its underlying reason is mutation in UNC13D gene which encodes Munc13-4 protein.

METHODS

For the first time, we aimed to systematically review clinical features, immunologic data, and genetic findings of patients with FHL3. We conducted electronic searches for English-language articles in PubMed, Web of Science, EMBASE, and Scopus databases to collect comprehensive records related to patients with UNC13D mutations.

RESULTS

A total of 279 abstracts were initially reviewed for inclusion. Among them, 57 articles corresponding to 322 individual FHL3 patients fulfilled our selection criteria. Finally, 73 and 249 patients were considered as severe and mild feature groups, respectively. Our results confirmed that fever, hepatosplenomegaly, and hemophagocytosis are common clinical features in the disease. Moreover, reduced fibrinogen and NK cell activity, as well as increased ferritin and triglycerides, are important markers for early diagnosis of the FHL3 disease. Investigation of genotype showed that the most prevalent type and zygosity of UNC13D are splice-site errors and compound heterozygous, respectively.

CONCLUSION

FHL3 patients have a wide range of clinical manifestations, which makes it difficult to diagnose. Therefore, it seems that the sequencing of the entire UNC13D gene (coding and non-coding regions) is the most appropriate way to accurate diagnosis of FHL3 patients.

Histoplasmosis-Associated Hemophagocytic Lymphohistiocytosis: A Review of the Literature

Background

Histoplasmosis is an endemic fungal disease with diverse clinical presentations. Histoplasmosis-associated hemophagocytic lymphohistiocytosis (HLH) is a rare disorder with limited data regarding treatment and outcome. We described the clinical features, treatment, and outcomes of five patients in our institution with histoplasmosis-associated HLH. This review also summarizes the current literature about presentation, treatment, and outcome of this infection-related HLH entity.

Methods

We searched the electronic medical records for patients with histoplasmosis-associated HLH at our institution from 1/1/2006 to 9/30/2017. Diagnosis of HLH was confirmed by chart review using the HLH-04 criteria. We also searched the current literature for case reports and case series.

Results

Five cases of histoplasmosis-associated HLH were included from our institution. All five patients were diagnosed after 2010. The literature review yielded 60 additional cases of histoplasmosis-associated HLH. The most common underlying condition was HIV in 61% of cases. The majority of histoplasmosis patients (81%) were treated with amphotericin B formulations. Documented specific treatments for HLH were as follows: nine patients received steroids only, six patients received intravenous immunoglobulin (IVIG) only, three patients received dexamethasone and etoposide, two patients received etoposide, dexamethasone, and cyclosporine, two patients received steroids and IVIG, and one patient received Anakinra and IVIG. The inpatient case fatality rate was 31% with most of the deaths occurring within two weeks of hospital admission.

Conclusions

Histoplasmosis-associated HLH among adults is an uncommon but serious complication with high associated mortality. Early antifungal therapy with a lipid formulation amphotericin B is critical. The initiation of immunosuppressive therapy with regimens like HLH-04 in this disease entity should be individualized.

Hyperferritinemia as a Diagnostic Marker for Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral disease in East Asia with high mortality. Few studies have examined markers that suggest SFTS in febrile patients. To determine useful biochemical markers for SFTS, patients aged 18 years or older with SFTS or microbiologically confirmed community-onset bacteremia with thrombocytopenia (BT) at presentation between June 2013 and December 2015 were included from two tertiary university hospitals in Republic of Korea retrospectively. Eleven patients with SFTS and 62 patients with bacteremia and thrombocytopenia were identified in the study period. Age and sex did not show significant difference among two groups. Fever was more commonly observed but comorbidities were less common in SFTS than in BT (P < 0.05, each). The areas under the curves of serum ferritin, C-reactive protein, white blood cell count, serum procalcitonin, and fibrinogen were above 0.9, indicating the discriminative power of these biomarkers (1.000, 0.991, 0.963, 0.931, and 0.934, resp., all P < 0.05). The optimal cutoff value of serum ferritin was 3,822 ng/mL in this study. These results suggest that hyperferritinemia is a typical laboratory feature of SFTS, and the serum ferritin level can be used as a marker for clinicians suspecting SFTS.

Extremely High Ferritinemia Associated with Haemophagocytic Lympho Histiocytosis (HLH)

Hyperferritinemia (>10,000 ng/ml) is an important hallmark used as an indicator of infection triggered macrophage activation syndrome leading to hemophagocytic lympho histiocytosis (HLH). Measurement of serum ferritin can be used in diagnosis as well as disease monitoring indicator and prognosis related to HLH, cAPS, sepsis, neoplasm and inflammatory conditions. It is a major contributor to manage critically ill patients as predicting and monitoring indicator. It can be used as acute phase response in conditions of MAS, AOSD, cAPS etc. A case study in our hospital showed extremely high ferritin values along with low hemoglobin, elevated LDH and triglycerides with positive MRSA in sputum culture and macrophage proliferation and hemophagocytosis in the bone marrow examination. Patient showed definite inverse relation with steroid therapy and serum ferritin levels.

Diagnostic Value of Common Inflammatory Markers on Fever of Unknown Origin

This study was designed to evaluate the diagnostic value of common inflammatory markers with regard to fever of unknown origin (FUO). We investigated 383 patients who were hospitalized with FUO at the Henan Province People's hospital between January 2009 and June 2015. Of all the cases, infectious diseases accounted for 33.9%, neoplasms for 21.1%, collagen vascular diseases for 25.1%, miscellaneous diseases for 4.7%, and no diagnosis for 15.1%. Patients in the neoplasm group were older than those in the infectious disease, collagen vascular disease, and miscellaneous disease groups (p = 0.006, p < 0.0001, and p = 0.001, respectively). The duration of fever before admission of patients in the neoplasm and collagen vascular disease group was longer than that of patients in the infectious disease group (p = 0.002 and p = 0.007, respectively). The diagnostic time after admission of patients from the neoplasm and collagen vascular disease groups was longer than that for patients from the infectious disease group (both p < 0.0001). Serum ferritin levels of patients in the infectious disease group were lower than those of patients in the neoplasm and collagen vascular disease groups (p = 0.029 and p = 0.032, respectively), while serum procalcitonin (PCT) levels in the infectious disease group was higher than that in the neoplasm and collagen vascular disease groups (p = 0.016 and p = 0.007, respectively). Therefore, FUO remains a clinical problem in China and serum ferritin and PCT may be useful in discriminating infectious from non-infectious causes (neoplasms and collagen vascular diseases) in patients with FUO.

Histoplasmosis-Induced Hemophagocytic Syndrome: A Case Series and Review of the Literature

Background. Histoplasmosis-associated hemophagocytic lymphohistiocytosis (HLH) is a relatively rare disorder for which data are limited regarding optimal treatment and clinical outcomes in adults. We describe the clinical features, treatment, and outcomes of patients with histoplasmosis-associated HLH at our institution.

Methods. We performed a retrospective chart review of all inpatients at Parkland Hospital diagnosed with HLH associated with Histoplasma capsulatum from 2003 to 2013.

Results. Eleven cases of histoplasmosis-associated HLH over this time period were identified. Nine of eleven cases were males (82%). Nine of these patients had human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), 1 was a renal transplant patient on immunosuppressants, and the other had no documented immunocompromise. The most common HLH criteria were splenomegaly (n = 10), fever (n = 10), and ferritin >500 ng/dL (n = 9). Urine Histoplasma antigen was positive in every patient tested (n = 9 of 9), and most antibodies for Histoplasma were positive if checked (n = 4 of 5). A majority of patients received liposomal amphotericin B (n = 9) with an average treatment duration of 11 days, and 5 patients also received prednisone, intravenous immunoglobulin (IVIG), or both. Overall, 5 patients died within 30 days (45.5%), and 7 patients died within 90 days (63.6%). Of the 5 patients that received immunosuppression, 4 died (80%), whereas in the group not given additional immunosuppression (n = 5), 2 died (40%).

Conclusions. Histoplasmosis-associated HLH among adults is a lethal disease of highly immunocompromised patients, especially patients with HIV/AIDS. Clinical features such as splenomegaly, elevated ferritin, and cytopenias should prompt evaluation for HLH in this population. Further data are needed to define the role of immunosuppression, IVIG, and highly active antiretroviral therapy in treating this condition.

Hemophagocytic syndrome complicating lung resection

A 68-year-old man underwent a left upper lobectomy for squamous cell lung carcinoma. After 15 days, he was readmitted with fever, dyspnea, and a skin rash. Computed tomography showed a pleural effusion, which was drained. He was diagnosed with hemophagocytic syndrome in view of the fever, skin rash, bicytopenia, hypertriglyceridemia, high lactate dehydrogenase, and raised ferritin levels. His clinical condition deteriorated in spite of steroid therapy, and he died on the 23rd postoperative day.

Hemophagocytic syndrome after liver transplantation: report of two cases

We report two cases of hemophagocytic syndrome (HPS), a rare but fatal complication after living-donor liver transplantation (LDLT). Despite their recovery from pancytopenia following treatment with steroid pulse therapy, granulocyte stimulating factor, and intravenous γ-globulin, both patients died. The outcomes reported in cases published in English are devastating, with only 4 survivors among the total 14 patients including ours. Pancytopenia is frequently recognized postoperatively in liver transplant recipients, although its cause is difficult to establish. When pancytopenia accompanying persistent high fever is recognized in LDLT recipients, HPS should be suspected and bone marrow aspiration performed as promptly as possible because of the poor prognosis of this syndrome. There is still no optimal treatment for HPS after liver transplantation.

Viral infections associated with haemophagocytic syndrome

Haemophagocytic syndrome (HPS) or haemophagocytic lymphohistiocytosis (HLH) is a rare disease caused by a dysfunction of cytotoxic T cells and NK cells. This T cell/NK cell dysregulation causes an aberrant cytokine release, resulting in proliferation/activation of histiocytes with subsequent haemophagocytosis. Histiocytic infiltration of the reticuloendothelial system results in hepatomegaly, splenomegaly, lymphadenopathy and pancytopenia ultimately leading to multiple organ dysfunctions. Common clinical features include high fevers despite broad spectrum antimicrobials, maculopapular rash, neurological symptoms, coagulopathy and abnormal liver function tests. Haemophagocytic syndrome can be either primary, i.e. due to an underlying genetic defect or secondary, associated with malignancies, autoimmune diseases (also called macrophage activation syndrome) or infections. Infectious triggers are most commonly due to viral infections mainly of the herpes group, with EBV being the most common cause. HPS can be fatal if untreated. Early recognition of the clinical presentation and laboratory abnormalities associated with HPS and prompt initiation of treatment can be life saving. HPS triggered by viral infections generally does not respond to specific antiviral therapy but may be treated with immunosuppressive/immunomodulatory agents and, in refractory cases, with bone marrow transplantation.

Postrenal transplant hemophagocytic lymphohistiocytosis and thrombotic microangiopathy associated with parvovirus b19 infection

Persistent anemia is a known consequence of Parvovirus B19 (B19) infection following renal transplantation. However, to date, no description of B19-related hemophagocytic lymphohistiocytosis (HLH) exists in renal transplant recipients. We report a 24-year-old male kidney recipient, who presented with fever, severe anemia and allograft dysfunction two years following transplantation. Hyperferritinemia, hypertriglyceridemia, elevated serum lactate dehydrogenase, pancytopenia and fragmented red blood cells on the peripheral blood were also noted. Bone marrow examination revealed giant pronormoblasts and frequent histiocytes with intracellular hematopoietic elements, consistent with HLH. Renal allograft biopsy revealed closure of the lumen of glomerular capillaries and thickening of the capillary walls compatible with thrombotic microangiopathy. The presence of anti-B19 IgM antibody and viral DNA in the patient's serum (detected by real-time PCR) confirmed an acute B19 infection. Following high-dose intravenous immunoglobulin therapy, the anemia gradually resolved and renal function improved. As far as we know, this is the first report of B19-associated HLH and thrombotic microangiopathy in a renal transplant recipient.

Understanding organ dysfunction in hemophagocytic lymphohistiocytosis

OBJECTIVE

This review aims to help critical care clinicians maintain a high level of suspicion regarding the diagnosis of Hemophagocytic Histiolymphocytosis (HLH). It describes the clinical and laboratory features of HLH, outlines its pathophysiology and reviews the most frequent etiologies related to HLH. Prognostic factors and therapeutic options are also reported.

DATA SOURCES

Review of the literature.

RESULTS

The diagnosis of HLH relies on the association of clinical abnormalities and hemophagocytosis in bone marrow, spleen, or lymph node specimens. Liver, pulmonary, renal, cardiac and skin involvement may occur at various degrees possibly leading to multiple organ failure. Three main etiologies can be found, namely infections, lymphoproliferative diseases, or connective tissue diseases. Immune deficiency is often retrieved. Mortality can be as high as 50%. Although clinically mimicking severe sepsis, HLH has a distinct pathophysiology on which specific therapy is based. Early diagnosis and treatment is mandatory to increase the chances of survival.

CONCLUSION

The comprehensive management of severe HLH requires the involvement of a multidisciplinary team in order to determine the best therapeutic strategy and to identify the underlying cause.

Tuberculosis-associated haemophagocytic syndrome

Haemophagocytic syndrome is a disorder characterised by fevers, lymphadenopathy, hepatosplenomegaly, cytopenias, and hyperferritinaemia due to dysregulated activation and proliferation of macrophages, leading to uncontrolled phagocytosis of platelets, erythrocytes, lymphocytes, and their haematopoietic precursors throughout the reticuloendothelial system. Primary or familial haemophagocytic syndrome appears to have a genetic aetiology, whereas secondary haemophagocytic syndrome may be associated with malignancy, autoimmune disease, or infection. Epstein-Barr virus is the most common infectious aetiology implicated in haemophagocytic syndrome, but the syndrome has been associated with a variety of other viral, bacterial, and parasitic pathogens. We describe a case of haemophagocytic syndrome associated with disseminated Mycobacterium tuberculosis. We review all cases of M tuberculosis-associated haemophagocytic syndrome reported in the English language literature and discuss important issues pertaining to the epidemiology, diagnosis, and management of this disease.

Virological and immunological characteristics of a 19-year-old Japanese female with fatal outcome with Epstein-Barr virus-associated hemophagocytic syndrome

Hemophagocytic syndrome (HPS) is caused by the hyperactivation of T-cells and macrophages. The clinical characteristics associated with this disease result from overproduction of cytokines including interferon-gamma (INF-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6). HPS presents with fever, liver dysfunction, coagulation abnormalities, pancytopenia, and a benign histiocytic proliferation with prominent hemophagocytosis in bone marrow, lymph node, spleen, and liver. We describe a 19-year-old female with fatal HPS. She had been given corticosteroid every other day for systemic lupus erythematosus (SLE) without flare up. The causative underlying disease was acute primary Epstein-Barr virus (EBV) infection. EBV genomes were detected by the polymerase chain reaction (PCR). To measure the virus load we use a real-time PCR assay to quantify the amount of EBV DNA in peripheral blood lymphocytes, lung, kidney, brain and liver at autopsy. Further in situ hybridisation (ISH) and immunohistochemical studies demonstrated that Epstein-Barr virus encoded small RNA (EBER) was detected in CD8+ T-cells in bone marrow, lung, kidney, brain, liver and spleen. In each organ, mRNA levels of inflammatory cytokines (INF-gamma, TNF-alpha, IL-6) were highly detected compared with beta-Actin mRNA levels. These results suggest that EBV-infected CD8+ T-cells in each organ (peripheral blood lymphocytes, lung, kidney, brain and liver) may have an integral role in the pathophysiology of the HPS.

Reactive hemophagocytosis associated with the initiation of highly active antiretroviral therapy (HAART) in a patient with AIDS

Reactive hemophagocytosis has been associated with neoplasia, bacteria, parasitic, and viral infections including human immunodeficiency virus (HIV). Here we present a case of reactive hemophagocytosis associated with the initiation of highly active antiretroviral therapy (HAART), probably representing a syndrome termed the immune reconstitution inflammatory syndrome (IRIS) or immune reconstitution syndrome.

Tuberculosis-Associated Hemophagocytic Syndrome in a Hemodialysis Patient with Protracted Fever

Hemophagocytic syndrome (HPS) is a clinicopathological reflection of uncontrolled activation of macrophages. To our knowledge, only a few cases of tuberculosis-associated HPS in hemodialysis have been reported in the English literature. We report a case of tuberculosis-associated HPS during hemodialysis. Bone marrow aspiration showed histiocytosis with hemophagocytosis; in addition, results of acid-fast staining and polymerase chain reaction showed the presence of acid-fast bacilli. Mycobacterium tuberculosis was subsequently cultured from sputum. The patient received late treatment with antituberculosis agents combined with intravenous immunoglobulin and had a poor response. On the basis of the results in this case, we recommend early bone marrow and tuberculous examination for patients undergoing maintenance hemodialysis who have fever of unknown origin.

Hemophagocytic syndrome: an unusual manifestation of acute human immunodeficiency virus infection

An 18 year-old heterosexual man was hospitalized because of fever, chills, a sore throat, and a dry cough for 8 days. He had had sexual intercourse with a new partner within the 4 months prior to admission. At admission, the patient presented a clinical picture compatible with hemophagocytic syndrome (HPS). The presence of hemophagocytosis was subsequently determined pathologically from bone marrow and lymph node specimens. An exhaustive diagnostic work-up failed to reveal any causative etiology, the symptoms improving after 2 doses of intravenous immunoglobulin (IVIG) infusion, given at a dose of 0.5 mg/kg each, the 2 doses being administered 1 week apart. Three months subsequent to the patient's initial presentation, acute human immunodeficiency virus (HIV) infection was diagnosed, and the patient received highly active antiretrovirus therapy (HAART) from the time of diagnosis. The patient remained well for the following 2 years. HPS in the advanced stages of HIV infection has previously been described, but HPS during seroconversion of an acute form of the infection is rare. We most definitely suggest, however, that acute HIV infection be included in the list of potential causes of HPS. IVIG therapy appears to be an appropriate therapeutic modality, and HAART also is effective, for prevention of recurrence of HPS in a patient with acute HIV infection.

Hemophagocytic syndrome associated with bilateral adrenal gland tuberculosis

We report a case of a patient who presented with hemophagocytic syndrome (HPS) and adrenal crisis associated with bilateral adrenal gland tuberculosis, and resulted in a poor outcome. A 50-year-old man was transferred to our hospital from a local clinic due to fever, weight loss, and bilateral adrenal masses. Laboratory findings showed leukopenia, mild anemia, and elevated lactate dehydrogenase. Computed tomography (CT) of the abdomen revealed bilateral adrenal masses and hepatosplenomegaly. CT-guided adrenal gland biopsy showed numerous epithelioid cells and infiltration with caseous necrosis consistent with tuberculosis. Bone marrow aspiration and biopsy showed significant hemophagocytosis without evidence of malignancy, hence HPS associated with bilateral adrenal tuberculosis was diagnosed. During anti-tuberculosis treatment the patient showed recurrent hypoglycemia and hypotension. Rapid ACTH stimulation test revealed adrenal insufficiency, and we added corticosteroid treatment. But pancytopenia, especially thrombocytopenia, persisted and repeated bone marrow aspiration showed continued hemophagocytosis. On treatment day 41 multiple organ failure occurred in the patient during anti-tuberculous treatment and steroid replacement.

Candidiasis-associated hemophagocytic lymphohistiocytosis in a patient infected with human immunodeficiency virus

We describe a patient with acquired immunodeficiency syndrome who developed candidiasis-associated hemophagocytic lymphohistiocytosis (HLH), and we review the previously reported cases of this unusual clinical syndrome in patients infected with human immunodeficiency virus (HIV). HLH appears to follow a fulminant course in HIV-infected patients, which warrants an aggressive diagnostic and therapeutic approach. HIV itself may play a role in the pathogenesis of HLH, which is usually associated with opportunistic infections or malignancies. Therapy is usually directed at supportive care and treatment of the underlying disorders, although initiation of antiretroviral therapy may improve the eventual outcome in some cases.

Reactive hemophagocytic syndrome associated with disseminated histoplasmosis in a heart transplant recipient

We describe a patient who developed multi-organ failure with reactive hemophagocytic syndrome secondary to disseminated histoplasmosis 8 months after orthotopic heart transplantation. The patient responded fully to a prolonged course of therapy with amphotericin B and remains free of recurrence. Disseminated histoplasmosis and reactive hemophagocytic syndrome have rarely been described in the setting of cardiac transplantation and never before in combination.

Hemophagocytic syndromes and infection

Hemophagocytic lymphohistiocytosis (HLH) is an unusual syndrome characterized by fever, splenomegaly, jaundice, and the pathologic finding of hemophagocytosis (phagocytosis by macrophages of erythrocytes, leukocytes, platelets, and their precursors) in bone marrow and other tissues. HLH may be diagnosed in association with malignant, genetic, or autoimmune diseases but is also prominently linked with Epstein-Barr (EBV) virus infection. Hyperproduction of cytokines, including interferon-gamma and tumor necrosis factor-alpha, by EBV- infected T lymphocytes may play a role in the pathogenesis of HLH. EBV-associated HLH may mimic T-cell lymphoma and is treated with cytotoxic chemotherapy, while hemophagocytic syndromes associated with nonviral pathogens often respond to treatment of the underlying infection.