Pfizer Inc. is teaming up with DNA testing company 23andMe to study the possible genetic underpinnings of inflammatory bowel disease, a hard-to-treat ailment that affects an estimated 1.4 million Americans.

Under the partnership, 23andMe will map the DNA of 10,000 patients who have forms of the disease, which include Crohn's disease and ulcerative colitis. Patients will submit saliva samples using 23andMe's at-home collection kit and then fill out online questionnaires about their disease and symptoms.

The companies say they hope to identify genetic similarities among patients with inflammatory bowel disease, which could guide development of targeted drugs to treat the disease.

The cause of inflammatory bowel disorders is unknown, though many scientists suspect genetics play a role. Other scientists believe the diseases are triggered by a virus or bacteria.