Which of the following statement(s) regarding ulcerative colitis is/are correct?

a. The most common age of onset for ulcerative colitis is in early adulthood

d. Approximately 10% to 25% of patients with ulcerative colitis have first degree relatives with the disease

Most cases of ulcerative colitis have onset between the ages of 15 and 40 years. While the age of onset may extend to old age, only 3% to 5% of the cases have onset after age 60. Males and females are affected equally frequently. Clear-cut familial patterns have been observed in ulcerative colitis. Ten to 25% of patients with this disease have first degree relatives with ulcerative colitis. Monozygotic twins have higher concordance for inflammatory bowel disease than dizygotic twins. Geographic as well as racial differences influence the occurrence of the disease. There is currently no definitive evidence regarding the role of genetic and environmental influences in the determination of familial patterns.