Psoriatic or cystic fibrosis arthropathy? Difficulty with diagnosis and management

A 19-year-old man with cystic fibrosis developed arthritis at the age of 12 years. He also suffered from psoriasis, and was found to be HLA-B27 positive. His disease was episodic in nature for the first 5 years, but he later developed an unremitting erosive arthropathy which proved difficult to treat.