This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
Pyoderma gangrenosum is seen in : 
Select and explain. 
A. Crohns disease, B. Diveuculosis, C. Ulcerative colitis, D. Ca. Colon
C: Ulcerative colitis
Answer: C: Ulcerative colitis 
Explanation: C. i.e. Ulcerative colitis Pyoderma gangrenosum occurs in both ulcerative colitis & Crohn's diseaseQ. But - 50% of PG occurs in association with UC. And - 2% of active UC patients have PG and another 4% UC patients have erythema nodosum. The mean duration of chronic ulcerative colitis before the appearance of erythema nodosum & PG is 5 & 10 years respectively.