11.   The twins were dressed alike.

12.   The twins were dressed differently and one was thinner than the other.

13.   Non-identical twins are the result of two fertilised eggs implanting in the uterus at the same time.

14.   One of the boys has a freckle on his cheek.

15.   Otherwise, the twins are nearly identical.

16.   Both twins were born healthy.

17.   Almost all affected twins were in clinical remission.

18.   Furthermore, this material offered an opportunity to study the IgG subclass pattern in inactive stages of inflammatory bowel disease because the affected twin were in clinical remission.

19.   They were, however, included in the analysis because, being monozygotic, these twins are genetically identical with those who ultimately developed inflammatory bowel disease.

20.   The affected ulcerative colitis twins were in clinical remission at the time of biopsy, and histological evaluation showed no signs of mucosal inflammation.