Hi . You may have seen me mention above that my wife, Kelly Mack, was diagnosed with a form of psoriasis. It was after many years of RA and her doctors did mention that her biologic may have been the trigger for it presenting, but there is no sure way to know. The main thing was getting the diagnosis and treatment. In her case the dermatologist did a biopsy to confirm what he thought. We have a sister-site for psoriasis and here is an article on the diagnostic process: https://plaquepsoriasis.com/how-diagnosed. You may also want to poke around the site some (the drop down "Menu" button at top left may be helpful). I will tell you that, in Kelly's case, it took the dermatologist to do the diagnosis. She developed a skin infection and ended up in the hospital and other doctors, including an infectious disease specialist, failed. Then she got to see her dermatologist and he diagnosed her in a couple of minutes and did the biopsy for confirmation. This is one of many reasons Kelly is a big fan of seeing specialists for the various aspects of her care (she wrote about that here: https://rheumatoidarthritis.net/living/specialist-treatment). Hope this information is helpful. Best, Richard (RheumatoidArthritis.net Team)