<qa>  What is the only study that uses ECP in Crohns disease?This is an unblinded, single-arm study of ECP in Crohns disease. This trial will use ECP twice a week every two weeks over 24 weeks during which time the dose of corticosteroids will be tapered. If the corticosteroids are able to be withdrawn without an increase in symptoms, then subjects may be eligible for further ECP twice a week every four weeks over 24 weeks as a maintenance regimen. 