 Rates, however, vary between different regions of the world from as few as 1 in 300 to as many as 1 in 40.In the United States it is thought to affect between 1 in 1750 (defined as clinical disease including dermatitis herpetiformis with limited digestive tract symptoms) to 1 in 105 (defined by presence of IgA TG in blood donors).Due to variable signs and symptoms it is believed that about 85% of people affected are undiagnosed.