ABSTRACT
Western countries. However, there is geographical variation. • The incidence shows a bimodal age distribution with the first
peak occurring between the ages of 15 and 30 years and the second peak occurring above the age of 50 years.
Western countries. However, there is geographical variation. • The incidence shows a bimodal age distribution with the first
peak occurring between the ages of 15 and 30 years and the second peak occurring above the age of 50 years.