SFTPD and relapsing polychondritis: IQR: interquartile range; RA: rheumatoid arthritis; SLE: systemic lupus erythematosus; SSc: systemic sclerosis; SjS: Sjögren's syndrome; MPA: microscopic polyangiitis; RP: relapsing polychondritis; TMP-SMX: trimethoprim-sulfamethoxazole; MTX: methotrexate; TAC: tacrolimus; eGFR: estimated glomerular filtration rate; KL-6: Krebs von den Lungen-6; SP-D: surfactant protein D; PCR: polymerase chain reaction; ST: trimethoprim-sulfamethoxazole.