**4. Epidemiology of HLH**

Until recently, it was widely believed that FHL because of genetic causes arose during infancy and early childhood. In a retrospective Swedish study the incidence of FHL was estimated to be 0.12/100,000 children per year (Henter et al., 1991b). With the more widespread availability of genetic testing, it is apparent that the first significant episode of HLH can occur throughout life from prenatal presentations through to the seventh decade.

There is no exact data on the incidence of any form of the acquired HLH. In 2007, a retrospective study was published analyzing HLH cases diagnosed in Japan between 2001 and 2005 (Ishii et al., 2007). The most frequent form of HLH in all age groups in Japan was EBV-associated HLH (35%; 163/469 pts), followed by other infection–associated HLH (29%; 138/469 pts), lymphoma–associated HLH (18%; 84/469 pts), autoimmune–associated HLH (11%; 53/496), FHL (4.5%; 20/469 pts) and post-HSCT (hematopoietic stem cell transplantation) HLH (2.5%; 11/469 pts). The authors estimated that the annual incidence of all types of HLH and in all age groups of Japanese patients was 1 case in 800,000 individuals per year (Ishii et al., 2007). However, this number is probably underestimated, due to the retrospective nature of the study, certain diagnostic difficulties and overlooking or misdiagnosing of some HLH cases. In the same study, the reported 5-year overall survival was highest in EBV- or other infection-associated HLH (> 80%) and in autoimmuneassociated HLH (almost 90%), intermediate in FHL or B-cell lymphoma-associated HLH

Autoimmune-Associated Hemophagocytic Syndrome/Macrophage Activation Syndrome 83

The reported incidence of juvenile idiopathic arthritis (JIA) varies from 1 to 22 cases per 100,000 children, with a prevalence of 8 to 150 cases per 100,000 children (Cassidy & Petty, 2005; Weiss & Ilowite, 2007). Of these, approximately 10% of patients have the systemic form of the disease (i.e., sJIA). It is estimated that approximately 7–10% of patients with sJIA develop life-threatening MAS (Janka, 2009; Sawhney et al., 2001), which may occur at any time during the course of the disease, with a mortality between 10–20%. Moreover, two studies suggested that a mild, subclinical form of MAS may be present in as many as 25– 30% patients with sJIA (Bleesing et al., 2007, Behrens et al., 2007). Although there are also numerous reports of MAS in adult onset Still's disease, SLE, and Kawasaki disease, the incidence of MAS in these entities is unknown. However, in considering MAS in general, the

The most typical signs of HLH are fever (duration ≥7 days, with peaks ≥38.5ºC) and splenomegaly associated with pancytopenia (affecting ≥2 cell lineages in peripheral blood), cerebromeningeal symptoms, skin rash, lymph node enlargement, jaundice and edema (Henter et al., 1991b; Kumakura, 2005; Öst et al., 1998; Reiner & Spivak, 1988). Laboratory findings include hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, liver function abnormalities (i.e., elevated transaminases and bilirubin), hypoproteinemia, and hyponatremia (Henter et al., 1991b, 1998, 2007; Janka et al., 1998). Histopathological examination reveals accumulation of lymphocytes and histiocytes (macrophages), sometimes with hemophagocytic activity, observed in the spleen, bone marrow, liver, lymph nodes and cerebrospinal fluid (Henter & Nennesmo, 1997; Henter et al., 2007; Janka, 2009; Öst et al., 1998). The histological picture of liver biopsy resembles chronic persistent hepatitis (Henter et al., 2007). In the brain the leptomeninges and perivascular spaces are involved (Akima & Sumi, 1984; Henter & Nennesmo, 1997). Other typical findings in HLH are low natural killer (NK) cell activity and high levels of the alpha chain of the soluble interleukin-2 receptor (sIL-2R, also named sCD25) in serum and CSF (Henter et al., 2007; Janka, 2009). Soluble IL-2R (together with an elevated level of ferritin) is a marker of generalized inflammation, but very high levels of sIL-2R are almost never seen outside of HLH (Filipovich, 2009). Normal ranges of sIL-2R vary with age being highest in infants, and lower in teenagers and adults. All the key clinical and laboratory features of HLH can be explained by hypercytokinemia and organ infiltration as shown in Table 2

Another important marker of HLH is soluble CD163 (sCD163). The macrophage hemoglobin scavenger receptor CD163 is restricted in its expression exclusively to cells of the monocyte– macrophage lineage (Schaer et al., 2005). The extracellular part of the protein is shed into plasma (sCD163), because of proteolytic cleavage upon macrophage activation. Thus, sCD163 is a reliable clinical marker of disorders associated with overwhelming macrophage activity (Filipovich, 2009; Grom & Mellins, 2010; Schaer et al., 2005). Because sIL-2R and sCD163 are soluble molecules shed from the surfaces of activated T cells and macrophages, respectively, their levels are likely to increase in the serum regardless of the tissue

AAHS/MAS may exhibit all of the characteristic features of HLH. Coagulopathy and cardiac impairment are common (Janka, 2009). Neurological symptoms in MAS may progress to a severe encephalopathy and coma. Of note, not all patients with

mortality rate is presumably about 8–22% (Gupta & Weitzman, 2010).

**5. Clinical and laboratory features of HLH and AAHS/MAS** 

(Janka, 2009).

localization of these cells (Grom & Mellins, 2010).

(50%), and lowest in T/NK-cell lymphoma-associated HLH (< 15%) (Ishii et al., 2007). A recent retrospective population-based study revealed the annual incidence of M-HLH in adults to be 1:280,000 per year or 0.36/100,000 individuals per year (Machaczka et al., 2011a). The results of this study were limited by the small population of the Swedish region of northern Halland, but the long observation period of over 14 years strengthened these findings.


HLH – hemophagocytic lymphohistiocytosis; EBV – Epstein-Barr virus; CMV – cytomegalovirus; HSV – herpes simplex virus; ND – not determined; sJIA – systemic onset juvenile idiopathic arthritis; NHL – non-Hodgkin lymphoma; MDS – myelodysplastic syndromes; AML – acute myeloid leukemia; ALL – acute lymphoblastic leukemia; MM – multiple myeloma; SCT – stem cell transplantation.

Table 1. The contemporary classification of different HLH forms

(50%), and lowest in T/NK-cell lymphoma-associated HLH (< 15%) (Ishii et al., 2007). A recent retrospective population-based study revealed the annual incidence of M-HLH in adults to be 1:280,000 per year or 0.36/100,000 individuals per year (Machaczka et al., 2011a). The results of this study were limited by the small population of the Swedish region of northern Halland, but

HLH – hemophagocytic lymphohistiocytosis; EBV – Epstein-Barr virus; CMV – cytomegalovirus; HSV – herpes simplex virus; ND – not determined; sJIA – systemic onset juvenile idiopathic arthritis; NHL – non-Hodgkin lymphoma; MDS – myelodysplastic syndromes; AML – acute myeloid leukemia; ALL –

acute lymphoblastic leukemia; MM – multiple myeloma; SCT – stem cell transplantation.

Table 1. The contemporary classification of different HLH forms

the long observation period of over 14 years strengthened these findings.

The reported incidence of juvenile idiopathic arthritis (JIA) varies from 1 to 22 cases per 100,000 children, with a prevalence of 8 to 150 cases per 100,000 children (Cassidy & Petty, 2005; Weiss & Ilowite, 2007). Of these, approximately 10% of patients have the systemic form of the disease (i.e., sJIA). It is estimated that approximately 7–10% of patients with sJIA develop life-threatening MAS (Janka, 2009; Sawhney et al., 2001), which may occur at any time during the course of the disease, with a mortality between 10–20%. Moreover, two studies suggested that a mild, subclinical form of MAS may be present in as many as 25– 30% patients with sJIA (Bleesing et al., 2007, Behrens et al., 2007). Although there are also numerous reports of MAS in adult onset Still's disease, SLE, and Kawasaki disease, the incidence of MAS in these entities is unknown. However, in considering MAS in general, the mortality rate is presumably about 8–22% (Gupta & Weitzman, 2010).

### **5. Clinical and laboratory features of HLH and AAHS/MAS**

The most typical signs of HLH are fever (duration ≥7 days, with peaks ≥38.5ºC) and splenomegaly associated with pancytopenia (affecting ≥2 cell lineages in peripheral blood), cerebromeningeal symptoms, skin rash, lymph node enlargement, jaundice and edema (Henter et al., 1991b; Kumakura, 2005; Öst et al., 1998; Reiner & Spivak, 1988). Laboratory findings include hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, liver function abnormalities (i.e., elevated transaminases and bilirubin), hypoproteinemia, and hyponatremia (Henter et al., 1991b, 1998, 2007; Janka et al., 1998). Histopathological examination reveals accumulation of lymphocytes and histiocytes (macrophages), sometimes with hemophagocytic activity, observed in the spleen, bone marrow, liver, lymph nodes and cerebrospinal fluid (Henter & Nennesmo, 1997; Henter et al., 2007; Janka, 2009; Öst et al., 1998). The histological picture of liver biopsy resembles chronic persistent hepatitis (Henter et al., 2007). In the brain the leptomeninges and perivascular spaces are involved (Akima & Sumi, 1984; Henter & Nennesmo, 1997). Other typical findings in HLH are low natural killer (NK) cell activity and high levels of the alpha chain of the soluble interleukin-2 receptor (sIL-2R, also named sCD25) in serum and CSF (Henter et al., 2007; Janka, 2009). Soluble IL-2R (together with an elevated level of ferritin) is a marker of generalized inflammation, but very high levels of sIL-2R are almost never seen outside of HLH (Filipovich, 2009). Normal ranges of sIL-2R vary with age being highest in infants, and lower in teenagers and adults. All the key clinical and laboratory features of HLH can be explained by hypercytokinemia and organ infiltration as shown in Table 2 (Janka, 2009).

Another important marker of HLH is soluble CD163 (sCD163). The macrophage hemoglobin scavenger receptor CD163 is restricted in its expression exclusively to cells of the monocyte– macrophage lineage (Schaer et al., 2005). The extracellular part of the protein is shed into plasma (sCD163), because of proteolytic cleavage upon macrophage activation. Thus, sCD163 is a reliable clinical marker of disorders associated with overwhelming macrophage activity (Filipovich, 2009; Grom & Mellins, 2010; Schaer et al., 2005). Because sIL-2R and sCD163 are soluble molecules shed from the surfaces of activated T cells and macrophages, respectively, their levels are likely to increase in the serum regardless of the tissue localization of these cells (Grom & Mellins, 2010).

AAHS/MAS may exhibit all of the characteristic features of HLH. Coagulopathy and cardiac impairment are common (Janka, 2009). Neurological symptoms in MAS may progress to a severe encephalopathy and coma. Of note, not all patients with

Autoimmune-Associated Hemophagocytic Syndrome/Macrophage Activation Syndrome 85

lineages (Hb <90 g/l; PLT <100 × 109/l; neutrophils <1.0 × 109/l), (4) hypertriglyceridemia (fasting triglycerides >3.0 mmol/l) and/or hypofibrinogenemia (<1.5 g/l), (5) hemophagocytosis in bone marrow, spleen, or lymph nodes, (6) hyperferritinemia (>500 µg/l), (7) low or absent NK-cell activity, (8) elevated level of sIL-2R (sCD25) >2400 U/ml. The last three HLH criteria were introduced in the revised diagnostic guidelines for HLH in

There are no validated diagnostic criteria addressed exclusively for AAHS/MAS, and early diagnosis is often difficult (Filipovich et al., 2010; Fukaya et al., 2008; Grom & Mellins, 2010). In general, in a patient with persistently active underlying rheumatologic disease, a fall in the ESR and platelet count, particularly in combination with persistently high CRP and increasing levels of serum D-dimer and ferritin, should raise a suspicion of impeding MAS (Grom & Mellins, 2010). According to Janka, a C-reactive protein >100 mg/l, increased granulopoiesis with left shift in the bone marrow and peripheral blood, and s-ferritin concentration >10,000 μg/L (if EBV infection has been excluded) are features strongly suggestive of MAS (Janka, 2009). The diagnosis of MAS is usually confirmed by demonstration of hemophagocytosis in the bone marrow, liver, lymph nodes, etc. However, false negative results may occur owing to sampling errors, particularly at the early stages of the syndrome (Grom & Mellins, 2010; Janka 2009). In some patients, subsequent biopsies may reveal hemophagocytic macrophages. In patients with negative bone marrow biopsies, assessment of the levels of sIL-2R and sCD163 in serum may help with the timely diagnosis

In particular, application of the HLH diagnostic criteria to sJIA patients with suspected MAS is problematic. Some of the HLH markers such as lymphadenopathy, splenomegaly, and hyperferritinemia are common features of active sJIA itself and therefore do not distinguish MAS from a conventional systemic JIA flare (Davi et al., 2011; Grom & Mellins, 2010). Other HLH criteria, such as cytopenias and hypofibrinogenemia, become evident only at the late stages. This is related to the fact that sJIA patients often have increased white blood cell and platelet counts and elevated s-fibrinogen as a part of the inflammatory response in sJIA. Therefore, when they develop MAS, they demonstrate cytopenias and hypofibrinogenemia to the extent seen in HLH only at the later stage of MAS, when its management becomes challenging (Davi et al., 2011; Grom & Mellins, 2010). Diagnosis of MAS is even more problematic in SLE patients with autoimmune cytopenias, which are difficult to distinguish from cytopenias caused by MAS (Carvalheiras et al., 2010; Grom & Mellins, 2010; Parodi et al., 2009). In these patients, the presence of extreme hyperferritinemia and elevated LDH should raise suspicion of MAS (Parodi et al., 2009). Attempts to modify the HLH criteria to increase their sensitivity and specificity for the diagnosis of MAS in rheumatic conditions

of MAS (Grom & Mellins, 2010; Komp et al., 1989; Schaer et al., 2005).

have been initiated and continue today (Ravelli et al., 2005; Davi et al., 2011).

developing severe AAHS/MAS in the course of their autoimmune disorder.

**7.1 MAS complicating juvenile arthritis and ankylosing spondylitis** 

Here we present three illustrative cases of patients with different autoimmune diseases

A 31-year-old male was referred from community hospital to the University Hospital (The Second Chair of Internal Medicine, Collegium Medicum, Jagiellonian University, Krakow,

2004 (Henter et al., 2007).

**7. Case presentations** 


HLH – hemophagocytic lymphohistiocytosis; IL – interleukin; TNF – tumor necrosis factor; sIL-2R – soluble IL-2 receptor (also named sCD25).

Table 2. Signs and symptoms of HLH and their causes

autoimmune/autoinflamatory diseases and MAS fulfill at the beginning diagnostic criteria for HLH (Janka, 2009). In patients, who already have signs of inflammation such as high leukocytosis, elevated platelet count, and elevated levels of fibrinogen, a decline in these parameters, without reaching pathological values, may herald MAS (Ravelli et al., 2005). MAS as a first symptom of sJIA may be indistinguishable from other cases of HLH when arthritis is missing. A high interleukin-1β concentration in blood may also suggest MAS rather than classic HLH (Janka, 2009; Henter et al., 1996). Although mild elevation of sIL-2R has been reported in many rheumatic diseases including JIA and SLE, a several-fold increase in the levels of sIL-2R in these diseases is highly suggestive of MAS (Grom & Mellins, 2010). Importantly, other clinical entities associated with high levels of sIL-2R include malignancies and some viral infections, such as viral hepatitis, and so these conditions should be considered in the differential diagnosis. Nevertheless, sIL-2R receptor and sCD163 are now increasingly recognized as important biomarkers of AAHS/MAS (Filipovich, 2009; Grom & Mellins, 2010).
