Hemophagocytic Lymphohistiocytosis: A Single Institution Experience
Authors: Ramadas Poornima , Leibovitch Jennifer , Gentile Teresa 
Published: November 2019

Background:
Hemophagocytic lymphohistiocytosis [HLH], is a rare life-threatening syndrome of excessive immune activation. It can be primary due to genetic predisposition or secondary due to infections, immune disorders or malignancies. With nonspecific clinical presentation, a high index of suspicion is required to make the diagnosis. Prompt treatment of underlying etiology and HLH specific therapy is warranted to prevent adverse clinical outcome.
Methods:
After IRB approval, we conducted a retrospective chart review of adult patients (pts) ≥ 18 years diagnosed with HLH between January 1st, 2010 and June 30th, 2019. We recorded age at diagnosis, gender, cause of HLH, symptoms, laboratory testing, bone marrow pathology, imaging, treatment and outcome.
Results:
We found a total of 15 patients in the time interval. Pt age ranged from 22 to 64 years with a median of 46 years. 60% were females and 40% were males. 14 pts had secondary HLH and one pt tested positive for HLH gene mutations. Etiology of HLH was malignancy in 6 (40%), infection in 5 (33%), rheumatological disease in 3 (20%) and cause was unclear in one pt but suspected to be an infection. One pt had prior allogenic stem cell transplant and one pt developed HLH even after completion of treatment for lymphoma.
On presentation, 14 (93%) had fever, 6 (40%) had respiratory symptoms, 6 (40%) had neurological symptoms, 2 (13%) had a skin rash, 2 (13%) had bleeding manifestations and 3 (20%) required pressor support. Hemoglobin ranged from 5.5 to 13.3 g/dL on presentation, with median of 10.1 g/dL and 14 (93%) had Hb <9 g/dL. Absolute neutrophil count ranged from 0.3 to 16.94 x 103/uL with median of 2.87x103/uL and decreased to < 1000x103/uL in 11 (73%) and < 500x103/uL in 7 (46%). Platelet counts on presentation ranged from 18 to 244x103/uL with median of 82x103/uL and decreased to <100x103/uL in 14 (93%) and <20x103/uL in 8 (53%). 14 (93%) had bicytopenia. Initial ferritin levels ranged from 1,552 to 2,62,080 ng/ml with median of 5,515 ng/ml and increased to >10,000 ng/ml in 10 (66%) and highest level was 4,57,970 ng/ml. All 15 pts had some degree of hepatic dysfunction and one pt had acute kidney injury. Triglyceride levels were >265 mg/dL in 6 (40%). 10 (66%) had laboratory evidence of disseminated intravascular coagulation (DIC), one pt had clinical DIC. Blood cultures were negative in everyone, except 2 pts who developed infection during the hospital course, one with Candida krusei and the other with methicillin sensitive staphylococcus aureus. Bone marrow biopsy was performed in 14 (93%) and all of them demonstrated hemophagocytosis. 3 (20%) underwent lumbar puncture and 2 had elevated CSF protein. 11 (73%) had immunological testing and all of them had elevated soluble IL-2 receptor alpha (sCD25 or sIL-2R). Of the 3 pts who had HLH genetic testing, one had HLH associated mutations.
Organomegaly was noted in 11 (73.3%) (4 had hepatosplenomegaly, 6 had splenomegaly, one had hepatomegaly). 6 (40%) had lung infiltrates. MRI brain was done in 5 (33%) and 2 had patchy hyperintensities.
11 (73.3%) were treated with HLH-94 protocol with etoposide and dexamethasone. One pt had matched unrelated donor Allogenic stem cell transplant. 13 (86.6%) had initial recovery. At the time of data cut off, 10 (66%) were alive. Of the 3 pts who initially recovered, one pt died of relapsed lymphoma, one died of HLH relapse and one developed Clostridium difficile infection with bowel perforation. [Refer to Table 1].
Conclusion:
Even though literature suggests that malignancy associated HLH has a worse prognosis, our small series did not suggest that. We also noted that HLH associated with rheumatological diseases leads to a superior outcome if the underlying disease is adequately treated. The most significant finding in our series was a patient with diffuse large B cell lymphoma who was diagnosed to have primary HLH with HLH associated mutations. Typically, primary HLH presents in the first few years of life. This patient case points to the fact that patients with primary HLH can have a late presentation and can also be associated with immunological disorders with a predisposition to malignancy. This finding suggests that all patients diagnosed with HLH should have genetic testing done for HLH associated mutations, as this will impact treatment decisions and these patients will benefit from more intense treatment which may include an allogenic stem cell transplant.

Disclosures
No relevant conflicts of interest to declare.