Methods and kits for diagnosing or predicting the risk of developing psoriatic arthritis in a subject in need of such diagnosis or risk prediction are provided, comprising measuring the expression level of one or more miRNAs disclosed herein in the sample of the subject, and compared the expression level of at least one of the miRNAs in the test sample with that of the psoriatic arthritis-free sample. Also provided are methods of treating psoriatic arthritis by reducing the expression level of at least one of the miRNAs disclosed herein.