Ulcerative colitis is understood to be the result of an overactive immune system. Certain factors that play a role include:
Genes – If a parent or other family member has UC, it increases the chances of you developing this disease
Other immune disorders – If an individual has one type of immune disorder, your chances of developing a second autoimmune disease is much higher.
Environmental Factors – Bacteria, virus & antigens may trigger your immune system.

ULCERATIVE COLITIS
Inflammatory Bowel Disease refers to a group of diseases which affect the GI Tract. Ulcerative colitis is a form of IBD which results in inflammation of colon or rectum or both.

Symptoms
Signs & symptoms differ from one person to another and they even tend to change overtime. People with Ulcerative colitis may experience periods of remission where the symptoms are almost nil. But, remission does not last forever, symptoms tend to come back and in some cases, may be severe. This is called a UC flare up