Adult cancer-related hemophagocytic lymphohistiocytosis – a challenging diagnosis: a case report

Background Adult hemophagocytic lymphohistiocytosis is a secondary immunopathologic phenomenon, mainly secondary to malignancy, infection, or autoimmune disorders. The performance of diagnostic criteria, studied in the pediatric population, is yet to be validated in the adult population. Some of the criteria include cytopenias and organomegaly that are inherent features to malignant processes, thus making the diagnosis of hemophagocytic lymphohistiocytosis a challenge in patients with cancer. Case presentation We describe the case of a 54-year-old white man with history of metastatic maxillary sinus adenoid cystic carcinoma who had severe liver injury and cytopenias with progressive clinical deterioration. We performed an evaluation, by flow cytometry, of the expression of surface markers in his natural killer cells that revealed remarkable abnormalities. His syndrome eventually fulfilled criteria for hemophagocytic lymphohistiocytosis and he received therapy with steroids with interval clinical improvement. Unfortunately, he refused further cytotoxic treatment and died 2 weeks later. Conclusions The conventional criteria for the diagnosis of hemophagocytic lymphohistiocytosis are suboptimal for adult patients with cancer resulting in delays in diagnosis and timely initiation of treatment. The diagnostic criteria have to be re-evaluated in patients with cancer; novel, easily available, and accurate diagnostic methods are needed.


Background
Hemophagocytic lymphohistiocytosis (HLH) is a lifethreatening immunopathologic syndrome with increasing prevalence in adults, necessitating systematic characterization and development of adult-specific criteria. Early recognition and diagnosis is critical with <10% survival without prompt treatment [1]. The HLH-2004 criteria offer a basis for clinical consideration, yet lack validation in the adult population [2]. Criteria such as cytopenias and organomegaly are inherent to malignant processes, especially hematologic or metastatic disease or concomitant chemotherapy.
We present a case of malignancy-related HLH with clinical manifestations that represented diagnostic ambiguity and difficulty in therapy initiation. We also describe the potential use of the evaluation of surface markers in cytokine-producing natural killer (NK) cells and cytotoxic NK cells by flow cytometry for diagnosis of that entity. Finally, we synthetize a literature review exploring current and developing HLH diagnostic criteria, as well as barriers to therapy, in particular for malignancy-related HLH.

Case presentation
A 54-year-old white man with a past medical history of right maxillary sinus adenoid cystic carcinoma with metastatic lesions to lung and vertebrae, hypertension, hypothyroidism, and nonalcoholic steatohepatitis presented to our emergency room in June 2016 with mental status changes accompanied by abdominal pain, dyspnea, and fever. He was not on active therapy for his malignancy. He previously received a trial regimen of coenzyme Q10, 12 g every 3 days, from October 2015 to April 2016. His past medical history was remarkable for two prior episodes of ascites and 3 months of progressive liver dysfunction and coagulopathy (Table 1). He had atorvastatin-induced myalgias leading to its discontinuation in April 2016 although his creatine kinase levels were not elevated. He was taking increasing doses of acetaminophen (2 grams daily) prior to admission. His physical examination vital signs were stable with one recorded febrile episode. In general, he appeared ill and lethargic, and was only oriented to person. He exhibited diminished bibasilar breath sounds, ascites with guarding, hypoactive bowel sounds, right lower quadrant tenderness, and hepatosplenomegaly.
Laboratory data were remarkable for hyperferritinemia, hypofibrinogenemia, anemia, and thrombocytopenia along with elevated transaminases and coagulopathy (Table 1). A peripheral blood smear showed neutrophilia, monocytosis, and reticulocytopenia. No microangiopathic changes were seen. Extensive platelet clumping was noted.
He continued to deteriorate with multiple organ failure including renal failure, myocardial injury, and respiratory failure requiring intubation. Empiric therapy, considering the evidence of liver injury and the possibility of HLH, with N-acetylcysteine on a 20-hour intravenous protocol and dexamethasone 8 mg intravenously administered three times daily was initiated. HLH chemotherapy was not done during this time as hepatotoxicity risk outweighed benefits and a definite diagnosis was not confirmed.
As an attempt to expedite the evaluation of possible HLH, we isolated mononuclear cells from peripheral blood and evaluated expression of surface markers in cytokine-producing NK cells and cytotoxic NK cells by flow cytometry. We compared the profile with normal controls. The results, available after 36 hours, were remarkable for an increased expression of CD69 in  Our patient's bone marrow biopsy was performed 10 days after admission and delayed due to severe coagulopathy and demonstrated normocellularity (40 to 50%), megakaryocytic hypoplasia, and clusters of foamy histiocytes with ingested marrow cells. Fifteen days after admission, he fulfilled multiple HLH-2004 diagnostic criteria including hyperferritinemia, fever, splenomegaly, cytopenias, hemophagocytosis on biopsy of bone marrow, elevated CD25, and decreased NK cell activity by standardized studies (Table 1).
He steadily recovered with the steroid therapy instituted for 12 days and supportive measures. He was weaned off intubation and sedation. However, he refused further interventions for HLH, namely etoposide-based therapy and continuation of steroid treatment; he chose palliative care and died 2 weeks later.

Discussion
Adult onset HLH is mainly a secondary phenomenon, arising from four components of pathology: a susceptible host; intrinsic/acquired immune defects; a trigger resulting in immune activation; and immunopathology resulting in host end organ failure [3]. Adult patients with HLH are immunocompromised individuals with malignancy, infection, or autoimmune disorders. Ramos-Casals et al.  found that 48% of cases were triggered by neoplasms, especially hematologic malignancies. Furthermore, patients with active malignancy are at greatest risk [4][5][6]. Differentiation of HLH from other sequelae of hematologic malignancies is based upon degree of inflammation [7]. Allen and McClain hypothesized that the syndrome results from complex interactions of host genetics and extrinsic immune challenges [7]. Studies have shown that immune defects in genes affecting regulation of granule-dependent lymphocyte activity as well as intracellular granule trafficking, mutations in T cell functioning (CD27), and cytokine production, that is, interferon (IFN)-gamma and interleukin (IL)-6, by malignant cells play a key role in HLH evolution [5,8]. Similar genes and inflammatory responses may become affected during neoplasm therapy, inciting an iatrogenic HLH in adults [9][10][11]. The HLH-2004 criteria, validated in the pediatric community, are consensus criteria developed to guide inclusion and enrollment to studies [7]. The sensitivity and specificity of these criteria in the adult population have yet to be validated through prospective studies. However, a recent study from the MD Anderson Cancer Center (MDACC) identified an "extended 18-point diagnostic criteria" of clinical and laboratory variables closely associated with a diagnosis of malignancy-associated HLH (M-HLH) in adults. Sensitivity analysis suggested that individuals with an underlying malignancy who met 5/18 criteria could be considered to have a high likelihood of M-HLH [6]. These extended criteria include available parameters at the community level such as serum albumin, serum transaminases, lactate dehydrogenase, and basic coagulation testing that may function as early effective surrogates of M-HLH. These 18 markers are currently being validated in a prospective clinical trial at MDACC (NCT02385110).
HLH consensus definitions implicate specific cell lines responsible for the severe inflammatory propagation, including: CD8+ T lymphocytes overactivation and uncontrolled expansion and NK cell dysfunction. Familial HLH (FHL) studies identified genetic deficiencies in these cell lines [3,7,12]. More recently, flow cytometry has been used to screen genetically predisposed patients, measuring intracellular perforin levels in NK cells [13]. To the best of our knowledge, similar flow cytometry studies, as described in our case, have not been conducted in adult patients with secondary HLH. Although well documented in patients with malignancies, NK cell line alterations may ultimately lead to secondary HLH. Various mechanisms of NK cell anti-tumor activity inhibition have been described, including: downregulation of NK-activating receptors, that is, natural cytotoxic receptors (NCRs) and NKG2D; upregulation of inhibitory receptors, that is, killer-cell immunoglobulin-like receptors (KIRs) and NKG2A; and modifications of expression of receptor-specific ligands. Ultimately, this inhibits NK cell-mediated anti-tumor surveillance, and impairs molecular crosstalk between NK cells and other immune cells [14]. Another study noted that excessive CD8+ T cells activation during FHL suppressed the regulatory T cell (Treg) population, allowing for rapid growth of CD8+ T-cell line and unchecked progression of persistent systemic inflammation. This resulted in an overall reduction of IL-2 and reversal in the IL-2 hierarchy of consumption by T cells, with pathologic preferential consumption by inflammatory CD8+ T cells via upregulated CD25, release of sCD25 by CD8+ T cells, reduction in Treg cell IL-2-induced anti-inflammatory properties, and reduction in Treg cell lines; this ultimately resulted in diverting "the normally anti-inflammatory IL-2 feedback loop into a proinflammatory circuit" [13].
Another major problem is the lack of effective therapy. Hurdles to therapy initiation, similar to our case report, include: (a) delayed recognition of HLH, (b) advanced stage of underlying disease, and (c) concurrent immunocompromised state with a need for further cytotoxic HLH-directed therapy. However, our experience with adult HLH suggests that early suspicion and treatment are of paramount priority as high mortality rate is secondary to the aggressive and rapid HLH process [6]. Emerging non-cytotoxic therapies such as IFN-gamma inhibitor (NI-0501), anti-IL-6 agents (tocilizumab), and JAK-inhibitors (ruxolitinib), either as single agents or in combination with traditional HLH therapies, hold promise for the therapy of M-HLH in adults.

Conclusions
The current diagnostic criteria of HLH might be suboptimal for adult patients and perhaps result in delays in its diagnosis and timely initiation of treatment. Given the high prevalence of cancer in an ageing population, current diagnostic criteria have to be re-evaluated in adult patients and novel, easily available, and highly specific diagnostic methods must be developed.

Funding
This study was supported in part by the MD Anderson Cancer Centre Support Grant (CCSG) CA016672.

Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Authors' contributions MAH jointly conceived the idea for the manuscript (with CMR, BRB, ND), searched the background literature, wrote the report, and refined the text in accordance with comments from all authors. BRB conceived the idea for the manuscript, contributed to drafting of the manuscript and final approval of the version to be published. DLB collaborated with acquisition and analysis of flow cytometry data, drafting of the manuscript, and final approval of the version to be published. ND conceived the idea for the manuscript, contributed to drafting of the manuscript and final approval of the version to be published. CMR was the lead physician responsible for the clinical care of the case,