# P-1940. Incidence and Outcomes of Pneumocystis carinii Pneumonia in Autoimmune Inflammatory Rheumatic Diseases in Korea: Nationwide study

## TL;DR

This study examines the occurrence and outcomes of a serious lung infection in patients with autoimmune diseases in Korea, finding that preventive treatment does not significantly reduce infection risk.

## Contribution

The study provides new insights into the effectiveness of prophylactic treatment for Pneumocystis pneumonia in autoimmune disease patients using nationwide data.

## Key findings

- PJP incidence was 0.14% among autoimmune disease patients.
- Prophylactic treatment did not significantly reduce PJP risk or mortality after matching.
- Certain subgroups showed elevated PJP risk despite prophylaxis.

## Abstract

Pneumocystis jirovecii pneumonia (PJP) remains a life-threatening opportunistic infection among immunocompromised individuals, particularly those with autoimmune inflammatory rheumatic diseases (AIIRDs) due to the use of high-dose corticosteroids and other potent immunosuppressive agents. Although prophylactic strategies have been recommended, their effectiveness and risk profiles in AIIRD populations remain unclear. To assess the incidence and outcomes of PJP and evaluate the impact of prophylactic interventions among patients with AIIRDs using a nationwide population-based cohort.Table 1.Baseline characteristics of the study population according to prophylaxis before and after propensity score matching

Baseline characteristics of the study population according to prophylaxis before and after propensity score matching

Continuous variables were described as mean and standard deviation (SD), and discrete variables were described as numbers and percentages (%).Table 2.Cox regression analysis of the incidence of Pneumocystis pneumonia in patients with AIIRDs before matchingContinuous variables were described as mean and standard deviation (SD), and discrete variables were described as numbers and percentages (%).

Cox regression analysis of the incidence of Pneumocystis pneumonia in patients with AIIRDs before matching

Continuous variables were described as mean and standard deviation (SD), and discrete variables were described as numbers and percentages (%).

Data were obtained from the Korean National Health Insurance Service database from 2010 to 2022. Patients with AIIRDs were identified using diagnosis and insurance codes and required immunosuppressive agent prescriptions. After applying strict operational definitions and exclusions, 111,152 patients were included. Prophylactic treatment was defined as the prescription of prophylactic agents for ≥90 days within one year of AIIRD diagnosis. Propensity score matching (1:1) resulted in two matched cohorts of 1,683 patients each. The primary outcomes were PJP incidence and all-cause mortality, evaluated using landmark analysis, Kaplan-Meier survival curves, and Cox proportional hazards models.Fig 1.Kaplan-Meier survival curves for all-cause mortality among patients with autoimmune inflammatory rheumatic diseases after propensity score matching

Kaplan-Meier survival curves for all-cause mortality among patients with autoimmune inflammatory rheumatic diseases after propensity score matching

Among the total cohort, 154 patients (0.14%) developed PJP. Risk factors for PJP included granulomatosis with polyangiitis, inflammatory myositis, antiphospholipid antibody syndrome, male sex, older age, corticosteroid use, JAK inhibitor use, and calcineurin inhibitor use. After matching, prophylactic treatment was not significantly associated with reduced PJP risk (HR, 1.586; 95% CI, 0.621–4.049; P = 0.3346) and was also not significantly associated with reduced mortality (HR, 1.063; 95% CI, 0.866–1.305; P = 0.5611).

PJP incidence in AIIRD patients was low but associated with substantial morbidity. Although prophylactic treatment showed no statistically significant impact on PJP incidence or mortality after matching, specific clinical subgroups exhibited markedly elevated risks. These findings support the need for individualized, risk-adapted prophylaxis strategies among AIIRD patients receiving immunosuppressive therapy.

All Authors: No reported disclosures