Severe pneumonia complicated by hemophagocytic lymphohistiocytosis in adults: a retrospective and exploratory clinical analysis

Background: Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening complication that can arise in adults with severe pneumonia (SP). This retrospective study analyzed the clinical characteristics, diagnostic approaches and treatment outcomes of adult patients diagnosed with SP complicated by HLH. Methods: The clinical data of 9 related adult patients were collected from the Department of Critical Care Medicine and analyzed. Results: The mean age of the patients was 41.11 +/- 13.02 years, with 88.9% (8/9) being male. Comorbidities included post-renal transplantation, lymphoma, pregnancy, hepatitis E, syphilis and hypertension. The observed 28-day mortality rate was 22.2% (2/9), while the 60-day to 1-year mortality rates were both 77.8% (7/9). The etiological agents responsible for SP included bacteria (16%), viruses (52%), fungi (28%) and chlamydia (4%). Chest computed tomography revealed bilateral multiple exudative lesions. All patients met the 2004 HLH diagnostic criteria and had a mean HScore of 246.78 +/- 44.11 and median ferritin level of 2828 mu g/L (Inter Quartile Range (IQR) 2284-5152). Bone marrow cytology revealed mononuclearphagocytic histiocytes in 8 of 9 patients. Lymphocyte subpopulations, including total lymphocyte count, cluster of differentiation (CD)4(+) and CD8(+) cells, were found to be significantly reduced (p < 0.01), while serum levels of interleukin (IL)-6 and IL-8 were markedly elevated (p < 0.001). Therapeutic interventions included targeted anti- infective treatment, with glucocorticoids administered to 5 patients, low-dose etoposide to 4 patients, intravenous immunoglobulin to 7 patients, and plasma exchange in 6 patients. Despite these interventions, mortality remained high. Conclusions: Routine monitoring of HLH diagnostic indicators in patients with SP is crucial, and anti-infective and supportive therapies, as well as immunosuppressive and cytotoxic agents, may offer potential benefits for critically ill patients.