Hemophagocytic Lymphohistiocytosis (HLH)- Symptoms, Signs and Diagnosis of a Rapidly Fatal Childhood Disease It is important for any physician to be able to early identify potentially life-threatening disorders in diseases that may lead to severe, permanent disabilities, in particular if they are treatable. Hemophagocytic lymphohistiocytosis (HLH) is such a disorder, although rare. The major aim of this presentation is to briefly present some signs and symptoms of this disease and to present the Diagnostic Guidelines of HLH. HLH usually affects children, and it may present in a number of ways. It may mimic a number of other diseases. As a chameleon, it may appear in various shapes, but it is an insidious chameleon. If the diagnosis is not made in time, the child may die or develop permanent disabilities. In its most typical form, it is clinically characterized by prolonged fever, hepatosplenomegaly and cytopenia (most commonly thrombocytopenia and anemia). Neurological symptoms may complicate and sometimes dominate the clinical course. Laboratory investigation may also reveal liver, coagulation and/or lipid abnormalities. The diagnosis may be difficult, and unfortunately a hallmark (hemophagocytosis) is commonly not found on the initial bone marrow examination. More common, early differential diagnoses include, among others, infectious mononucleosis, CMV, septicemia, malignancies (mainly leukemia and lymphoma), hepatitis, encephalitis, metabolic disorders, and various other infections, such as leishmaniasis. The primary form, familial hemophagocytic lymphohistiocytosis (FHL), typically seen during infancy and early childhood, is almost invariably fatal with a median survival without therapy of two months after onset. Importantly, the inheritance is recessive, and the family almost never knows the disease when their first child is affected. A secondary form, sometimes termed "virus-associated hemophagocytic syndrome" (VAHS) can affect all ages and is also associated with a high mortality. Both conditions are underdiagnosed. It is important to be aware of these diseases, since effective and potentially life-saving therapy is available. EpidemiologyMost patients develop the disease very early in life with around 70% being less than one year of age at onset, but familial forms have been reported up to the age of young adults. The disease may also present at birth or even at prenatal investigations. The disease has been reported from many ethnic groups. Since FHL is an autosomal recessive disease, an increased incidence has been reported in ethnic groups with consanguinity as part of the cultural tradition.
IncidenceIn a (Swedish) retrospective study, the incidence of primary HLH in children was estimated to be 0.12 per 100,000 children born per year, i.e. one per 50,000 live born. Similar figures have also been reported from Great Britain. This figure has to be considered the minimal incidence, and probably there are still patients who are not diagnosed. The male to female ratio is around 1:1. Common Symptoms and SignsThe symptoms may vary widely. The most common early findings are fever, hepatomegaly, and splenomegaly (Table 1). Other early symptoms include a skin rash, lymph node enlargement, and neurological abnormalities. The fever is frequently undulent and protracted but may decline spontaneously. In a few children, it may develop late in the course of the disease. The splenomegaly and hepatomegaly are usually pronounced and progressive. The rash is uncharacteristic, transient, and often associated with high fever. Lymph node enlargement develops in less than half of the patients but may occasionally be marked. It is not difficult to imagine that differential diagnoses may include infectious mononucleosis and other viruses, as well as septicemia or chronic, systemic, inflammatory disorders. More rarely, some children may initially be diagnosed and treated as having chronic, persistent hepatitis or acute, fulminant hepatitis. Common Laboratory FindingsCytopenia, in particular thrombocytopenia but also anemia and to a lesser degree neutropenia, is common already at onset of the disease (Table 2). Hypertriglyceridemia is a common finding in systemic disease with fever. Hepatic abnormalities including elevated serum transaminase or hyperbilirubinemia, both of which may be markedly elevated (>900 U/L and >300 micromol/L respectively), appear to be related to the degree of liver involvement. Elevated ferritin and lactate dehydrogenase, hyponatremia and low protein/albumin are other common findings which are associated with the general inflammatory condition. Coagulation abnormalities are common during active disease, in particular hypofibrinogenemia. Immune-system derangement with hypercytokinemia is typical and is probably mediating the symptoms. A striking finding in FHL patients is the low or absent natural killer (NK)- cell activity as well as T-cell cytotoxicity which is restored subsequent to bone marrow transplant (BMT). Neurological Symptoms, Signs, and Laboratory FindingsAlthough the signs of central nervous system (CNS) involvement may be pronounced already early, it is more common that they develop later during the course of the disease (Table 1). However, it is important to be aware that these symptoms sometimes may dominate the clinical course. The picture may include irritability, bulging fontanel, neck stiffness, hypotonia, hypertonia, and convulsions. Cranial nerve (VI-VII) palsy, ataxia, hemiplegia/tetraplegia, blindness, and unconsciousness may also develop, as well as nonspecific signs of increased intracranial pressure. In the spinal fluid, a moderate pleocytosis with mainly lymphocytes may be found (5-50x106/L), as well as elevated protein levels (Table 2). Note that caution with lumbar puncture must be taken with regard to a possibly increased intracranial pressure. MRI or CT of the brain may show abnormalities, in particular later in the course of prolonged disease, representing areas of past or ongoing inflammatory activity or demyelinization areas. Bleeding, atrophy and brain edema may be found. Hyperdense areas on CT may falsely be interpreted as calcifications. It is important to treat the disease prior to the development of permanent neurological disabilities. However, it may be difficult to establish the diagnosis. Differential diagnoses presenting with CNS problems include, among others, encephalitis, degenerative cerebral disorders, and neurometabolic disorders. Histopathology and CytologyThe major histological finding is a nonmalignant, mixed lymphohistiocytic accumulation in the reticuloendothelial system. The histiocytes appear activated, and hemophagocytosis is a typical but not specific finding. The hemophagocytosis mostly affects erythrocytes but occasionally also platelets and leukocytes. The organs most frequently involved are the spleen, liver, lymph nodes, bone marrow and CNS. Figure 1. Three active macrophages, all of them with signs of hemophagocytosis, mainly engulfed erythrocytes. Material from a fine needle aspiration biopsy of the spleen. 
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There are no histological and/or cytological findings that are specific for HLH, and the diagnosis must thus be based on additional clinical and laboratory investigations, including NK-cell activity and preferably also genetic studies. Mutations in the perforin gene affect 20-40% of affected individuals. A second gene defect that may cause the disease is mutations in the Munc13-4 gene. An examination revealing no evidence of hemophagocytosis does not rule out the possibility of HLH. On the contrary, it is common that the first bone marrow examination does not reveal hemophagocytosis.
Differential Diagnoses
To establish the diagnosis of FHL may indeed be very difficult, and the disease is probably still underdiagnosed. Two of the key factors with regard to the diagnostic difficulties are first, that the disease is uncommon and many physicians are thus not aware of it, and second, that the clinical picture varies markedly. As mentioned, there are less known presentations, such as one with encephalitis or other neurological symptoms, a picture resembling chronic, persistent hepatitis, or a neonatal onset that may be misdiagnosed as an overwhelming viral infection.
The hematological abnormalities may suggest differential diagnoses, such as leukemia, lymphoma, aplastic anemia, and myelodysplastic syndrome. In addition, there are a number of other diseases that may develop a "macrophage-activating syndrome," such as X-linked lymphoproliferative syndrome (XLP), Chédiak-Higashi syndrome, and Griscelli syndrome. Other histiocytic disorders are also among the differential diagnosis, in particular multisystem Langerhans cell histiocytosis.
Diagnostic Guidelines Are Available.
To facilitate the diagnosis, diagnostic guidelines have been developed by the Histiocyte Society (Table 3). The criteria included are based on common clinical, laboratory and histopathological findings.
According to these guidelines, the diagnosis of HLH requires that five out of eight criteria be fulfilled. First, there are the five initial criteria: 1) fever, 2) cytopenia (two of three lineages), 3) splenomegaly, 4) hypertriglyceridemia and/or hypofibrinogemia, and 5) hemophagocytosis. Then there are three recent criteria, being 6) low or absent NK-cell activity, 7) hyperferritinemia, and 8) high plasma levels of soluble CD25 (soluble 12-2 receptor). In addition, the diagnosis of FHL (familial HLH) is justified by a positive familial history, and parental consanguinity is suggestive (Table 3).
As mentioned above, primary and secondary forms of HLH may be difficult to distinguish clinically and histologically. Familial affection or parental consanguinity strongly suggests FHL. The onset of FHL is most common during the first two years of life. However, perforin defects have been reported in older children and adolescents. Secondary forms of HLH can be found in all ages, also in adults.
It is of utmost importance to be aware that, at least in some cases, the disease may not strictly adhere to the guidelines proposed and that atypical presentations also are to be expected. Also, a number of patients may develop one or more of the diagnostic criteria late during the course of the disease. Thus, in the absence of any specific marker of disease, therapy sometimes may have to be commenced on strong clinical suspicion of HLH, before overwhelming disease activity makes irreversible damage and a response to treatment less likely.
In addition, genetic analyses for diagnostic purposes are also available for FHL, including analyses for perforin and Munc 13-4 mutations. Moreover, perforin defects can also be detected by flow cytometry, in a more rapid fashion. . Referral to experienced centers for diagnosis and therapy is highly recommended.
Figure 2. Section from the brain in a child with advanced HLH in the CNS. There are large destroyed areas in the brain, leaving only empty holes (arrow).
Treatment
Without treatment, FHL is usually rapidly fatal with a median survival of about two months. The Histiocyte Society in 1994 developed a common treatment protocol (HLH-94), primarily designed for the primary, inherited disease FHL. This protocol has been moderately modified, and the present Histiocyte Society protocol is entitled HLH-2004. Intrathecal methotrexate and steroids are added in selected patients. The aim is first to achieve a clinically stable resolution and ultimately to cure by BMT. The protocols have been widely accepted internationally and used in more than 25 countries and on all continents.
There is a high remission rate on the HLH-94 and HLH-2004 treatment protocols, during which time a BMT donor usually can be identified. The overall prognosis with regard to survival improved dramatically during the last decade. One major problem is that many children still are diagnosed late, at a stage when they may have severe and irreversible brain damage.With regard to long-term survival, the prognosis will be dependent upon the results of BMT, which also are increasingly rewarding.
References
Henter J-I., Elinder G., Öst Å., and the FHL Study Group of the Histiocyte Society. "Diagnostic Guidelines for Hemophagocytic Lymphohistiocytosis." Semin. Oncol., vol. 18, no. 1, 1991, Feb, pp. 29-33.
Henter J-I., Aricò M., Elinder G., Imashuku S., Janka G. "Familial Hemophagocytic Lymphohistiocytosis (Primary HLH)." Hematol. Oncol. Clin. North Am., vol. 12, no. 2, 1998 Apr, pp. 417-433.
Janka G., Elinder G., Imashuku S., Schneider M., Henter J-I. "Infection- and Malignancy-Associated Hemophagocytic Syndromes: Secondary Hemophagocytic Lymphohistiocytosis." Hematol. Oncol. Clin. North Am., vol. 12, no. 2, 1998 Apr, pp. 435-444.
Stepp SE., Dufourcq-Lagelouse R., Le Deist F., Bhawan S., Certain S., Mathew PA., Henter J-I., Bennett M., Fischer A., de Saint Basile G., Kumar V. "Perforin Gene Defects in Familial Hemophagocytic Lymphohistiocytosis." Science, vol. 286, 1999, pp. 1957-1959.
Ericson KG., Fadeel B., Nilsson-Ardnor S., Söderhäll C., Samuelsson AC., Janka G., Schneider M., Gürgey A., Yalman N., Révész T., Egeler RM., Jahnukainen K., Storm-Mathiesen I., Haraldsson A., Poole J., de Saint Basile G., Nordenskjöld M., Henter J-I. "Spectrum of Perforin Gene Mutations in Familial Hemophagocytic Lymphohistiocytosis." Am. J. Hum. Genet, vol. 68(3), 2001 Mar, pp. 590-597.
Henter, J-I, Samuelsson-Horne AC, Aricò M, et al. "Treatment of Hemophagocytic Lymphohistiocytosis with HLH-94 Immuno-Chemotherapy and Bone Marrow Transplantation." Blood, vol. 100, 2002, pp. 2367-2373.
Feldmann, J, Callebaut I, Raposo G, et al. "Munc 13-4 is Essential for Cytolytic Granules Fusion and is Mutated in a Form of Familial Hemophagocytic Lymphohidtiocytosis (FHL3)." Cell, vol. 115, 2002, Nov, pp. 461-473
Table 1. Initial Clinical Findings in Familial Hemophagocytic Lymphohistiocytosis (FHL)
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|
Literature Review a (n=121) |
Population-based Study b (n=32) |
FHL Registry c (n=122) |
|---|---|---|---|
|
Fever |
98/108 (91%) |
29/32 (91)(100%d) |
114/122 (93%) |
|
Splenomegaly |
98/100 (98%) |
27/32 (84)(100%d) |
119/122 (97) |
|
Hepatomegaly |
94/100 (94%) |
28/31 (90) (97%d) |
n.a.e |
|
Lymph Node Enlargement |
17/100 (17%) |
13/31 (42)(52%d) |
39/122 (31%) |
|
Skin Rash |
7/108 (6%) |
13/30 (43)(65%d) |
30/122 (24%) |
|
Neurological Abnormalities |
n.a.e (20%d) |
6/30 (20)(47%d) |
n.a.e |
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Notes: Janka GE. "Familial Hemophagocytic Lymphohistiocytosis," Eur. J. Pediatr, vol. 140, 1983, p. 221, Henter J-I., Elinder G., Söder O., et al. "Incidence and Clinical Features of Familial Hemophagocytic Lymphohistiocytosis in Sweden," Acta. Paediatr. Scand., vol. 80, 1991, p. 428, Arico M., Janka G., Fischer A., et al. "Hemophagocytic Lymphohistiocytosis: Diagnosis, Treatment and Prognostic Factors. Report of 122 Children from the International Registry," Leukemia, vol. 10, 1996, p. 197, Symptoms found not only at onset but at any time in the disease n.a.= no data available. |
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Table 2. Initial Laboratory Findings of Familial Hemophagocytic Lymphohistiocytosis (FHL)
|
|
Literature Review a (n=121) |
Population-based Studyb (n=32) |
FHL Registry c (n=122) |
|---|---|---|---|
|
Anemia |
93/104 (89%) |
23/31 (71%)(94%d) |
n.a.e |
|
Thrombocytopenia (<100x109/L) |
77/94 (82%) |
26/28 (93%)(100%d) |
104/122 (85%) |
|
Neutropenia (<1x109/L) |
56/96 (58%) |
19/28 (68%)(87%d) |
73/122 (59%) |
|
Leukopenia (<4x109/L) |
38/98 (39%) |
16/28 (57%)(87%d) |
n.ae |
|
Hypertriglyceridemia |
25/30 (83%) |
4/5 (80%)(100%d) |
78/97 (80%) |
|
Hypofibrinogenemia |
26/35 (74%) |
3/3 (100%)(85%d) |
66/101 (65%) |
|
Alanine Aminotransferase Elevated |
about one-third |
12/20 (60%)(92%d) |
55/104 (53%) |
|
Bilirubin Elevated |
about one-third |
6/15 (40%)(74%d) |
n.a.e |
|
Hyponatremia |
frequent |
8/15 (53%)(79%d) |
n.a.e |
|
CSF Pleocytosis |
17/33 (52%) |
6/10 (60%)(91%d) |
55/94 (58%) |
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Notes: Janka G. "Familial Hemophagocytic Lymphohistiocytosis," Eur. J. Pediatr, vol. 140, 1983, p. 221, Henter J-I., Elinder G., Söder O., et al. "Incidence and Clinical Features of Familial Hemophagocytic Lymphohistiocytosis in Sweden," Acta. Paediatr. Scand., vol. 80, 1991, p. 428, Arico M., Janka G., Fischer A., et al. "Hemophagocytic Lymphohistiocytosis: Diagnosis, Treatment and Prognostic Factors. Report of 122 Children from the International Registry.," Leukemia, vol. 10, 1996, p. 197, Symptoms found not only at onset but at any time in the disease n.a.= no data available. |
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Table 3. Diagnostic Guidelines for HLH (revised from Henter et. al., Semin. Oncol., 1991; 18:29-33)
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The diagnosis of HLH can be established if one of either 1 or 2 below is fulfilled. Fever Splenomegaly Laboratory Criteria Cytopenias (affecting >2 of 3 lineages in the peripheral blood): Hemoglobin (<90 g/L) (In infants <4 weeks: Hgb <100 g/L) Platelets (<100x109/L) Neutrophils (<1.0x109/L) Hypertriglyceridemia and/or hypofibrinogenemia (fasting triglycerides >3.0 mmol/L (i.e. >265 mg/dL, fibrinogen ≤1.5 g/L) Histopathologic Criteria Hemophagocytosis in bone marrow, spleen, or lymph nodes. No evidence of malignancy.
Low or absent NK-cell activity (according to local laboratory reference). Ferritin > 500 microgram/L. Soluble CD25 (i.e. soluble IL-2 receptor) > 2400 U/ml. |
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Notes: The diagnosis of FHL is justified by a positive family history as well as disease-causing mutations in the perforin and Munc 13-4 genes, and parental consanguinity is suggestive. |
Comments:
If hemophagocytic activity is not proven at the time of presentation, further search for hemophagocytic activity is encouraged. If the bone marrow specimen is not conclusive, material may be obtained from other organs. Serial marrow aspirates over time may also be helpful.
The following findings may provide supportive evidence for the diagnosis:
Spinal fluid pleocytosis (mononuclear cells) and/or elevated spinal fluid protein,
Histological picture of the liver resembling chronic, persistent hepatitis (biopsy).
Other abnormal clinical laboratory findings consistent with the diagnosis are: cerebromeningeal symptoms, lymph node enlargement, jaundice, edema, skin rash, hepatic enzyme abnormalities, hypoproteinemia, hyponatremia, VLDL elevated, and HDL decreased.