During a pathology teaching session, a faculty member displays histological slides from two patients with inflammatory bowel disease. Patient A shows mucosal and submucosal inflammation with crypt abscesses and surface ulceration, but the muscularis propria is spared. Patient B shows transmural inflammation with non-caseating granulomas and fissuring ulcers. What is the most common extraintestinal manifestation associated with Patient A's condition?