Using the immunosuppressant medication methotrexate to treat psoriasis and psoriatic arthritis is more likely to lead to serious liver complications than using the same medication to treat rheumatoid arthritis, according to research from the Perelman School of Medicine at the University of Pennsylvania. That finding continued to be true even when controlling for other risk factors for liver disease such as obesity and alcohol use. The Penn researchers suggest that clinicians closely monitor the health and liver condition of their patients on methotrexate for the treatment of psoriasis and psoriatic arthritis. The study results are published in the Journal of the American Association of Dermatology.