Hemophagocytic lymphohistiocytosis secondary to Babesia in an immunocompetent adult.

Abstract

A 38-year-old Caucasian male presented to the hospital with nausea, vomiting, and fevers to 104.7 °F. Three days prior a diagnosis of influenza was made and oseltamivir was prescribed, with initial improvement in symptoms. However, anuria, acholic stools, jaundice, scleral icterus and arthralgias subsequently developed which prompted a visit to the Emergency Department (ED). The initial presentation including high fevers, nausea, and vomiting led to a presumptive diagnosis of sepsis due to persistent influenza infection. However, lack of response to oseltamivir and sudden onset of jaundice raised concern that these symptoms were due to an alternative diagnosis. Pertinent past medical history included type 1 diabetes mellitus (DM) managed with an insulin pump. No past surgeries were noted, and there was no personal or family history of gallbladder or liver disease. Additionally, there was no reported excessive use of alcohol, illicit drug use, unsafe sexual practices, or intake of over-the-counter supplements. He worked as a lawyer and denied toxic exposures. A history of a recent hiking trip in eastern Long Island was elicited upon further questioning. Family history was notable for several autoimmune conditions including type 1 DM and Sjogren's syndrome in his father, rheumatoid arthritis in his sister, and celiac disease in his nephew. Physical examination revealed a well-developed male in no distress, vital signs pertinent for a fever to 101.4 °F, scleral icterus, and a blanching, petechial rash on the lower extremities. Murphy's sign was negative. The reported symptoms may have resulted from hepatic or biliary pathology, but could also reflect other conditions which cause hyperbilirubinemia such as hemolytic anemia, infections, or autoimmune processes. The differential diagnosis of new-onset obstructive jaundice is broad, and etiologies range from acute cholecystitis, hepatitis B and C, hemolysis, tick-borne illnesses, and cholangiocarcinoma. There was no history of blood transfusions, exposure to viral hepatitis, or other condition associated with development of jaundice. Rarely, influenza virus can lead to liver failure, as described during the 2009 influenza pandemic where it was thought that hypoxia and increased activation of the systemic immune response lead to hepatocellular injury.1 Given the history of hiking, tick-borne diseases were added to the list of possible diagnoses. The most common tick borne diseases are Lyme disease, ehrlichiosis, Rocky Mountain spotted fever, tularemia, Colorado tick fever, tick borne relapsing fever, Q fever, and babesiosis.2 Lyme disease, ehrlichiosis, Q fever, and babesiosis are the tick-borne illnesses endemic to this geographical area and were higher on the list of possible diagnoses. The presentation of petechial rash was suggestive of severe thrombocytopenia, prompting further workup including a complete blood count (CBC), comprehensive metabolic profile (CMP), and laboratory tests for hemolysis. A CBC performed in the ED revealed decreased hemoglobin of 10.2 g/dL and platelets of 43 000/mm3; the white blood cell count was normal. As shown in Table 1 the hemoglobin concentration dropped to a nadir of 7.1 g/dL on day 5 of hospitalization, without any known blood loss. Electrolytes on initial CMP revealed reduced sodium 125 mEq/L and chloride 90 mEq/L, and normal potassium 3.9 mEq/L, bicarbonate 27 mEq/L, BUN 17 mg/dL, and creatinine 1.0 mg/dL; his anion gap was normal at 8. The hepatic profile showed an increased total bilirubin level of 12.1 mg/dL with a conjugated bilirubin level of 8.6 mg/dL. ALT and AST were elevated to 160 IU/L and 192 IU/L, respectively. Alkaline phosphatase was elevated to 286 IU/L. Haptoglobin was reduced to < 4 mg/dL. Lactate dehydrogenase (LDH) was elevated to 1134 IU/L. Both the direct and indirect bilirubin were elevated. Direct hyperbilirubinemia reflects the decreased ability of conjugated bilirubin to be cleared from the liver, and indirect hyperbilirubinemia raised suspicion for red blood cell hemolysis. The bilirubin levels plus the bicytopenia and elevated transaminases suggested that the jaundice was related to hemolysis, combined with acute hepatic dysfunction. In addition, the hemolytic anemia and severe thrombocytopenia were concerning for a microangiopathic process. A peripheral smear may suggest the diagnosis by allowing for visualization of fragmented red blood cells, or schistocytes, which are characteristic of a microangiopathies, such as thrombotic thrombocytopenic purpura (TTP), typical or atypical hemolytic uremic syndrome (HUS), and disseminated intravascular coagulation (DIC). Additionally, a peripheral smear may suggest a parasitic or tick-borne infection if intracytoplasmic red blood cell abnormalities are visualized. Lastly, a CT scan was ordered to evaluate for cholestasis or hepatocellular disease as the cause of hyperbilirubinemia. The peripheral smear revealed absence of schistocytes in all visualized high powered fields, though inclusion bodies were noted in a small proportion of neutrophils. Abdominal CT imaging showed mild enlargement of the spleen measuring 14.5 cm × 6.9 cm and a height of 15.2 cm. There was hepatomegaly with a liver span of 26.1 cm × 16.1 cm, and an approximate height of 20 cm, without masses (Figure 1 ). Enlargement of the liver along with edema of the anterior gallbladder wall was suspicious for hepatitis. The marked elevation of indirect bilirubin and LDH along with an acute decline of the hemoglobin and haptoglobin suggested a microangiopathic hemolytic anemia. However, the corresponding peripheral smear did not reveal any schistocytes, which decreased the likelihood of TTP, HUS, or DIC. A consultation with the hematology service was made as the constellation of symptoms was suspicious for hemophagocytic lymphohistiocytosis (HLH). HLH is an illness characterized by uncontrolled activation of lymphocytes and macrophages, and its disease presentation is highly variable.3 The gastroenterology service was also consulted for the acute hepatitis, which was initially believed to be of a viral etiology given the recently diagnosis with influenza. Additional work up revealed a markedly elevated ferritin level of 32 383 μg/L (normal range 12-300 μg/L) and soluble interleukin-2 receptor (sIL2R) level of 7274 U/mL (normal range 223-710 U/mL). Coombs testing for anti-C3D direct antiglobulins was positive. Peripheral flow cytometry was also performed but did not show immunophenotypic evidence of a lymphoproliferative disorder or leukemia. A bone marrow aspiration with biopsy was performed and results confirmed the presence of hemophagocytes (Figure 2). The symptomatology combined with these additional results ultimately fulfilled the diagnostic criteria for HLH (Supplemental Table S1). As macrophages are a primary repository for ferritin outside of the liver, HLH is typically associated with very high ferritin levels due to macrophage activation. In isolation, highly elevated ferritin is not sufficient for a diagnosis of HLH as a ferritin greater than 10 000 μg/L has been reported to have at best 76% sensitivity and 60% specificity in adults.4, 5 While hepatitis was likely secondary to HLH, there were no signs of parenchymal liver disease on abdominal imaging and the elevation of sIL2R further supports a diagnosis of HLH.6 A study evaluating the required level of sIL2R to diagnose HLH using the HLH-2004 criteria determined that a threshold of 2515 U/mL or higher is 100% sensitive and 72.5% specific.7 While hemophagocytosis may not always be present on histologic assessment,8 the findings on bone marrow biopsy further supported the diagnosis of HLH. With a working diagnosis of HLH, treatment was initiated based on the HLH-2004 protocol with 20 mg of dexamethasone (10 mg/m2; BSA = 2.09 m2) and 250 mg of cyclosporine twice daily (6 mg/kg in two divided doses; weight = 93 kg). Etoposide, which is part of this regimen, was initially held in light of hyperbilirubinemia. An evaluation by the infectious disease service was requested in the setting of persistent fevers. Given the intraerythrocytic inclusions on the peripheral smear, PCR testing for parasitic DNA was performed to investigate for tick-borne illnesses. Testing for Babesia microti DNA was positive on Wright staining, with 2.8% parasitemia, and azithromycin 500 mg twice a day with atovaquone 750 mg once a day was started in addition to the HLH-directed treatment. The plasma parasite load continued to downtrend after initiating antibiotics, and the parasitemia was eradicated after 5 days of antibiotic therapy. A 10 day course of these antibiotics was completed without any complications. The goal of HLH treatment is to suppress the hyperactivation of the immune system, including activated T cells that are thought to underlie the clinical sequelae. Of course, identifying and treating an underlying etiology is crucial as well as complex. It can be difficult to determine the etiology of HLH, because acquired causes can include an array of genetic syndromes, malignancies, rheumatological disorders, infections, or immune disorders. Treatment is typically given according to the HLH-2004 protocol devised by the Histiocyte Society which involves administration of etoposide, dexamethasone, and cyclosporine immediately, with a goal to reduce symptoms prior to hematopoietic stem cell transplantation (HSCT).9 Administering corticosteroids in addition to intrathecal methotrexate can be considered if patients have symptoms of central nervous system involvement.9 Given the presentation with elevated bilirubin levels, etoposide was delayed during the hospital admission due to concern that it might worsen the hepatitis. Pertinent family history also included autoimmune disorders in his father, sister, and nephew, suggesting a predisposition to autoimmune disease and immune system dysfunction. However, since this acute presentation occurred in conjunction with a Babesia infection, it was essential to treat the tick borne infection as it was likely the underlying etiology of the HLH. There was progressive clinical improvement and he was discharged on dexamethasone and cyclosporine; etoposide was not required for resolution of symptoms. He continued to see his hematologist once a week for 4 weeks, then at 2-, 3-, and 6-months following discharge. Improvements in his hemoglobin, platelets, and ferritin levels were noted (Table 1 ), without recurrence of symptoms. Complete tapering of cyclosporine and dexamethasone was achieved after the 2 month follow up. When a patient with HLH is discharged, close follow up is imperative in order to monitor blood counts, inflammatory markers, and recurrence of symptoms, as well as to complete the full course of HLH-directed therapy. If a patient does not improve with 2-3 weeks of treatment, salvage therapy needs to be considered, including a referral for consideration of HSCT if the patient is eligible. In this case, there was clinical resolution of the HLH at 8 months. The hemoglobin improved to 13.5 g/dL, platelets recovered to 300 000/mm3, and the ferritin level decreased to <200 μg/L. This case illustrates the importance of considering HLH as part of the evaluation of fever of unknown origin and unexplained cytopenias. HLH is an acute hematological disorder characterized by uncontrolled activation of lymphocytes and macrophages, leading to a robust pathologic immune response. HLH occurs in both primary and secondary forms. Primary, or genetic HLH, presents as familial HLH syndromes.10 Secondary HLH occurs as a result of inappropriate immune activation due to infection, malignancy, or metabolic etiologies.10-12 Additionally, macrophage activation syndrome is a form of HLH that is a complication of rheumatologic disorders, particularly systemic juvenile idiopathic arthritis or adult-onset Still's disease.10, 13 HLH has a variety of clinical presentations and may appear as a fever of unknown origin, hepatitis, acute liver failure, sepsis, or neurologic abnormalities.11 Diagnostic criteria were developed in 1994 by the Histiocyte Society, and these criteria have been further revised with publication of the HLH-2004 trial (Supplemental Table).14 Patients must fulfill five of the eight criteria for diagnosis. Our patient met six out of the eight criteria for the diagnosis of HLH, including fever, splenomegaly, anemia and thrombocytopenia, hyperferritinemia, elevated sIL2R, and a bone marrow biopsy demonstrating hemophagocytosis. In HLH, macrophages, dendritic cells, NK cells and cytotoxic T cells are activated; however, defective cytotoxic activity impairs down-regulation of the immune response leading to sustained immune activation.10 As mentioned above, HLH can be either primary or secondary forms. Primary HLH is genetic; inheritance occurs in either an autosomal recessive or X-linked pattern, and HLH episodes are often triggered by infection.10, 12 Mutations occur in perforin-1 (PRF1), Unc-13 homolog D (UNC13D), syntaxin 11 (STX11), and syntax binding protein-2 (STXBP2) genes which encode proteins involved in phagocytosis and cytolysis by immune cells.10, 12, 15 Secondary HLH can occur in the setting of infection or malignancy; potential etiologies include Epstein-Barr virus, herpes simplex virus, cytomegalovirus, NK cell leukemia, peripheral T-cell lymphomas, or B-cell lymphomas.10, 12 HLH has also been reported to be caused by tick borne diseases such as human granulocytic anaplasmosis, Ehrlichia chaffeensis, and Rickettsia, all of which are transmitted via ticks of the Ixodes genus.16-19 Babesiosis is a rare cause of HLH in immunocompetent adults that is transmitted through Ixodes scapularis, also known as the deer tick.20 Most cases occur in the Northeast and Upper Midwest with an increasing incidence over the past several decades.20 Babesia is an intraerythrocytic protozoal parasite that can cause lysis of erythrocytes resulting in mild hemolytic anemia, though generally the infection is self-limited in immunocompetent patients.20, 21 Severe infections may occur in immunosuppressed patients who have HIV, chronic cardiac or pulmonary disease, are post splenectomy, or are receiving immunosuppressive medications.21 Three previous cases of HLH secondary to Babesia have been reported in elderly immunocompetent patients.22-24 One additional case of HLH secondary to babesiosis was reported in 1986 in a 54 year old homosexual male who did not have any reported history of immunosuppression.25 The patient was diagnosed with HLH while he was febrile and found to have splenomegaly, anemia, thrombocytopenia, leukopenia, and demonstrated hemophagocytosis on his bone marrow aspirate.25 To our knowledge, our case is the first reported in an immunocompetent adult younger than age 40 who developed HLH secondary to Babesia. In our case, as well as in the previous four reported cases of HLH secondary to babesiosis, clinical improvement with symptom resolution occurred within 3-7 days of initiating antibiotics against babesia.22-25 Treatment of secondary HLH focuses on suppressing hyperactivated T cells and histiocytes as well as addressing the underlying etiology.14 The first standardized treatment of HLH was organized by the Histiocyte Society in 1994. Prior to the HLH-94 protocol, median survival for familial HLH was less than 2 months.11 The development of a standardized protocol increased the 3 year probability of overall survival to 55%, and 51% with familial cases.26 Treatment includes an 8 week induction with dexamethasone (10 mg/m2 for 2 weeks, 5 mg/m2 for 2 weeks, 2.5 mg/m2 for 2 weeks, 1.25 mg/m2 for 2 weeks), etoposide (150 mg/m2 twice weekly for 2 weeks, then weekly for 6 weeks), and intrathecal methotrexate (once weekly during weeks 3-6, maximum of four doses) if central nervous system involvement is present.6, 26 This protocol underwent revision in 2004, a major change involving the addition of 6 mg/kg of cyclosporine to the induction of dexamethasone and etoposide, with the aim of increasing immunosuppression with cyclosporine, without additional myelosuppression. Other major changes involve a shorter time to evaluation for HSCT and the addition of corticosteroids to intrathecal methotrexate.6 Despite these changes, significant improvements in outcomes were not noted with the HLH-2004 protocol in comparison with the HLH-94.27 Additional alternative treatments were also studied over a 14 year period where patients received corticosteroids and antithymocyte globulin followed by HSCT, and survival rates were comparable.27 Our patient was treated based on the HLH-2004 protocol, with induction with dexamethasone and cyclosporine, completed 4 weeks later. Etoposide was held initially due to acute liver dysfunction, and given his quick recovery, he did not require etoposide. Infection with Babesia microti, as in our case, can be treated with atovaquone and azithromycin.20, 21 Babesia microti DNA on PCR continued to decline until being completely eliminated during hospitalization. This case illustrates the varied presentation of secondary HLH and how outcomes can be improved by diagnosing and treating the underlying etiology as early as it can be identified. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.