Fever of Unknown Origin in Myelodysplastic Syndrome: Clinical and Laboratory Features of a Chinese Cohort

Background: Fever of unknown origin (FUO) is clinically challenging in the setting of myelodysplastic syndrome (MDS). This study aimed to describe the clinical and laboratory features of patients with MDS and FUO and to explore factors associated with in-hospital fever resolution. Methods: We conducted a retrospective, single-center observational study of hospitalized patients with MDS and FUO at Peking Union Medical College Hospital, China, between January 2013 and December 2022. Patients were categorized into treatment-responsive and treatment-unresponsive groups based on fever outcomes after treatment. Demographic, clinical and laboratory features were collected and compared between the two groups. Results: A total of 98 patients were screened and 89 were included in the study. In approximately 80% of patients, FUO presented as the initial manifestation of MDS. Over half of the patients had high or very high risk per the revised International Prognostic Scoring System (IPSS-R), and complex karyotypes were observed in 25.8% of patients. MDS subtype distribution differed significantly between the groups (p = 0.027). Lower-blast MDS (MDS-LB) was more common in the treatment-responsive group (70.3% vs. 48.1%), whereas increased-blast MDS (MDS-IB) was more frequent in the treatment-unresponsive group (16.2% vs. 42.3%). Mucocutaneous lesions were more frequent among treatment-responsive patients (54.1% vs. 21.2%; p = 0.002). A higher percentage of CD8+CD38+ T-cells was associated with favorable treatment response (66.7 [60.4,80.6] vs. 47.4 [38.5,57.7]; p = 0.003). In addition, use of glucocorticoids and immunosuppressants was significantly associated with fever resolution (p = 0.004 and p = 0.043, respectively). Conclusions: In this selected cohort, MDS patients with FUO were predominantly at high risk and carried unfavorable prognostic factors. Mucocutaneous presentation and elevated CD8+CD38+ T-cell proportions were associated with in-hospital fever improvement. The association between anti-inflammatory treatment and fever resolution suggests a possible immune-mediated contribution to fever in these patients. As no non-MDS FUO comparison group was included and long-term outcomes were not available, these findings should be regarded as descriptive and hypothesis-generating.