Clinical biomarkers associated with Pneumocystis jirovecii pneumonia among dermatology patients receiving systemic immunosuppression: a single-center retrospective study.

backgroundPneumocystis jirovecii pneumonia (PJP) is a rare but potentially fatal complication among dermatology patients receiving systemic immunosuppression. Data on early clinical biomarkers in this population remain limited.

objectivesTo identify clinical and laboratory biomarkers associated with PJP in patients with severe dermatologic diseases undergoing systemic immunosuppressive therapy.

methodsWe conducted a retrospective cohort study of hospitalized dermatology patients receiving systemic immunosuppression. Patients who developed PJP were included at the time of diagnosis, whereas non-PJP patients were required to remain free of PJP during at least 6 months of clinical follow-up after initiation of systemic immunosuppressive therapy. Given the limited number of PJP events, multivariable analysis was restricted to three clinically prioritized variables (initial glucocorticoid dose, LDH, and serum albumin) to avoid model overfitting, and Firth's penalized likelihood correction was applied to mitigate small-sample bias.

resultsAmong 636 patients with severe dermatologic diseases, 18 developed PJP (2.8%). The median interval from the diagnosis of the primary dermatologic disease to PJP onset was 60 days (IQR 30-110 days). Univariate analysis showed that PJP patients had significantly higher initial glucocorticoid doses, lower lymphocyte counts, lower serum albumin, and higher LDH and CRP levels (all P < 0.05). In exploratory multivariable logistic regression using Firth's penalized likelihood correction, elevated LDH (adjusted OR 1.006, 95% CI 1.003-1.014; P = 0.006) and decreased serum albumin (adjusted OR 0.68, 95% CI 0.43-0.87; P = 0.030) remained independently associated with PJP. ROC curve analysis showed good discriminatory performance for LDH (AUC 0.938; sensitivity 94.4%) and serum albumin (AUC 0.861; sensitivity 73.7%). The optimal internally derived cut-off values were 302.0 U/L for LDH and 28.5 g/L for serum albumin. These thresholds were derived from the same retrospective cohort and require external validation before clinical implementation.

conclusionsDynamic monitoring of LDH and serum albumin, particularly during the early months after initiation of systemic immunosuppression, may help raise clinical suspicion for PJP. Exceeding these thresholds should prompt closer surveillance and timely diagnostic evaluation, rather than automatically triggering prophylactic treatment. The cut-off values derived from this cohort are hypothesis-generating and require external validation; all findings should therefore be interpreted as exploratory.