DQ beta restriction fragment length polymorphism in insulin dependent diabetes mellitus.

HLA DQ beta restriction fragment length polymorphisms (RFLP's) were compared in 43 patients with insulin dependent diabetes mellitus (IDDM), 51 healthy first grade relatives of IDDM patients and 27 controls without IDDM heredity in their families. We were able to demonstrate an association between the presence of a 12 kb BamHI restriction fragment (p less than 0.001) and 12 kb/4 kb (p less 0.01) or 12 kb/4.4 kb (p less than 0.001) BamHI fragment combinations and IDDM. But for these fragments and fragment combinations we also found increased frequencies in the healthy first grade relatives of IDDM patients. That means for the evaluation of the importance of the characterised "risk fragments" in practice it is necessary to follow up the manifestation of IDDM in this risk group.