Acquired hypolipoproteinemia and hemophagocytic lymphohistiocytosis: A previously unexplored association?

e19041 Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare disease that is the result of macrophage hyperactivation, leading to disordered cellular phagocytosis that is highly fatal if left untreated. The precise precipitating factor that leads to HLH is presently unknown. Secondary HLH is more common in adults and has numerous causes, including several autoimmune diseases, rheumatological disorders, cancers, and infections. These predisposing conditions are similar in that they are characterized by increased rates of cellular replication and often accompanied by significant oxidative stress. Lipoprotein changes in HLH have not been previously described. Methods: Between August 2018 and June 2020, three cases of secondary HLH were discovered to have profound hypolipoproteinemia with severely reduced total cholesterol, undetectable LDL-C, and extremely depressed HDL-C levels. As a result, a retrospective review of the University of Michigan HLH registry was performed, identifying cases of HLH where full lipid panels were performed as part of their diagnosis and/or treatment between 2012 and 2020. 18 total patients were identified with a confirmed diagnosis of HLH and who had a full lipid panel performed as a part of their diagnostic evaluation. Results: 100% of patients were found to have HDL-C less than 30 mg/dL, consistent with severe HDL-C deficiency, and 84% had HDL-C less than 20 mg/dL. Similarly, 74% of patients were found to have LDL-C < 100 mg/dL, 47% with LDL-C < 50 mg/dL, and 33% had undetectable LDL-C levels. Median total cholesterol was 124 mg/dL, median LDL-C was 35 mg/dL, and median HDL-C was 7 mg/dL. Notably, these reductions were not explained by the observed variability in hypertriglyceridemia, and marked hypertriglyceridemia > 500 mg/dL was not seen in 88% of patients, with a median triglyceride value of 279. Interestingly, one patient displayed an opposite phenotype with extreme hyperlipidemia, with total cholesterol of 727 mg/dL and LDL-C of 658 md/dL. Conclusions: Severe derangements in circulating lipoproteins appear to be a common finding within sHLH.These findings have not been previously described within the context of the disease. Herein, we provide a framework for hypothesizing why HLH may potentially occur in the setting of hypolipidemia. Furthermore, we provide an additional hypothesis that serves to justify why these changes may occur in an evolutionary context.