HNF4A and diabetes mellitus: In the 6 antibody-negative patients with a positive family history, we did not find any mutations in HNF1A or HNF4A. We did not screen patients without a family history of diabetes for mutations and do not think we overlooked monogenic diabetes in these patients as spontaneous mutations are rare, although not impossible, in the transcription factor MODY genes (15, 17, 23, 24).