This is an open-labeled, prospective clinical study aims at collecting and analyzing baseline characteristics of autoimmune inflammatory rheumatic disease (AIIRD) patients receiving sulfanilamide for preventive purposes, as well as subsequent follow-up data, in order to assess the efficacy and safety of the medication. Additionally, through a stratified analysis of risk factors, the investigators aim to identify the AIIRD population that would benefit most from preventive medication based on a favorable benefit-risk ratio.

Inclusion Criteria:

1. The patient was diagnosed with AIIRD according to the International Classification of Diseases and had received steroids or immunosuppressive therapy;
2. The patient had not received standard PJP treatment before enrollment, including the first-line treatment drug TMP/SMZ, or other second-line treatment drugs (including Pentamidine, Atorvastatin, Caspofungin, etc.);
3. The patient was at least 18 years old at the time of enrollment;

Exclusion Criteria:

1. Serious health problems or diseases, including (but not limited to) the following: severe liver damage (ALT, AST elevated above normal value by more than 5 times), severe renal insufficiency (GFR < 30mL/min or Scr > 445umol/L), severe myelosuppression (Hb < 65g/L, PLT < 25×10^9/L or neutrophils < 0.5×10^9/L);
2. Screening test indicates infection with human immunodeficiency virus (HIV), history of lymphomatous hyperplasia of the lymphatic tissue or any malignant tumor of any organ system within the past 5 years, or history of organ transplantation;
3. Participants with a history of allergy to sulfonamide drugs, megaloblastic anemia due to folate deficiency;
4. Pregnant and lactating women;
5. Any medical or psychological condition that the investigator believes would interfere with the participant's ability to comply with the protocol or complete the study;
6. Patients who refuse to comply with the requirements of this study and complete the study;
7. Any other situation that the investigator considers unsuitable for participation in the study (for reasons including but not limited to management reasons).