IL31 and pemphigus foliaceus: The reverse Mendelian analysis reveals a positive causal relationship between PF and NPTX1 (p = 0.038, OR = 1.020, CI [1.001, 1.040]), IL31 (p = 0.040, OR = 1.019, CI [1.000, 1.038]), and CTSE (p = 0.030, OR = 1.022, CI [1.002, 1.042]).