Epidemiology, clinical characteristics, and genetic etiology of neonatal diabetes in Japan.

Neonatal diabetes mellitus (NDM) is a rare but potentially devastating metabolic disorder, with a reported incidence of one per 300 000-500 000 births generally, and hyperglycemia develops within the first 6 months of life. NDM is classified into two categories clinically. One is transient NDM (TNDM), in which insulin secretion is spontaneously recovered by several months of age, but sometimes recurs later, and the other is permanent NDM (PNDM), requiring lifelong medication. Recent molecular analysis of NDM identified at least 12 genetic abnormalities: chromosome 6q24, KCNJ11, ABCC8, INS, FOXP3, GCK, IPF1, PTF1A, EIF2AK3, GLUT2, HNF1β, and GLIS3. Of these, imprinting defects on chromosome 6q24 and the KCNJ11 mutation have been recognized as the major causes of TNDM and PNDM, respectively, in Caucasian subjects. Although the pathogenesis and epidemiology of NDM in Japan seem to be clinically distinct, they are still unclear. In this review, we summarize the epidemiology, clinical characteristics, and genetic etiology in Japanese patients with NDM compared with the data on Caucasian patients.