Epidemiology, Clinicopathological Features, Etiological Spectrum and Outcomes of Subcutaneous Mycoses: A 14-Year Retrospective Study

Background: Subcutaneous mycoses are a group of chronic deep fungal infections involving the skin and subcutaneous tissue. In this study, we characterized their epidemiology, diagnostic findings, treatment, and outcomes in a referral cohort from Beijing, China. Methods: We retrospectively reviewed 86 patients diagnosed with subcutaneous mycoses at a referral center in Beijing which serves a notable population from northeastern agricultural regions, from 2012 to 2025. Data on clinical presentations, microbiological and histopathological findings, diagnostic methods, treatment regimens, and outcomes were collected and analyzed. Results: A total of 86 patients were included, comprising 35 males (40.7%) and 51 females (59.3%). The median disease duration was 9.0 months. A history of trauma was recorded in 19 patients (22.1%). Sporothrix spp. were the predominant pathogens, accounting for 47 cases (54.7%), followed by filamentous fungi in 24 cases (27.9%), and yeasts and yeast-like fungi in 15 cases (17.4%). Underlying conditions affecting host defense were present in 22 patients (25.6%) and were most frequent in the yeast/yeast-like group (73.3%; p < 0.001). Histopathology was performed in 70 patients; fungal structures were seen in only 11.4%. Among 85 patients included in the outcome analysis, 72 (84.7%) achieved complete response. Complete-response rates differed among etiological groups (p = 0.004), and filamentous fungal infection was independently associated with non-complete response (OR, 6.46; 95% CI, 1.45–39.25; p = 0.014). Patients with underlying conditions affecting host defense had a lower complete-response rate than those without such conditions (66.7% vs. 90.6%; p = 0.014). Conclusions: The etiological spectrum of subcutaneous mycoses in this referral cohort was strongly influenced by epidemiological and host factors, with Sporothrix spp. predominating. Fungal culture remains central to etiological confirmation, while histopathology and mNGS provide complementary information. Pathogen category and host-defense status may help guide treatment stratification and follow-up.