Neonatal diabetes mellitus: chromosomal analysis in transient and permanent cases.

Objectives: To describe a large cohort of patients with transient neonatal diabetes mellitus (TNDM) and permanent neonatal diabetes mellitus (PNDM), and to investigate whether chromosome 6 analysis helps to distinguish TNDM from PNDM.
Study Design: Patients with TNDM (n = 29) (insulin therapy for <3 years) and 21 with PNDM were identified through a nationwide study.
Results: Although patients with PNDM were less likely to have had intrauterine growth restriction (36% vs 74% for TNDM, P <.006), were older at diagnosis (median: 27 vs 6 days, P <.01), and had higher initial insulin requirements (1.4 U/kg/day vs 0.6 U/kg/day, P <.006), no clinical features were reliable in distinguishing PNDM from TNDM on an individual case basis. Permanent insulin-dependent diabetes developed in 5 TNDM patients after 8 years of age, emphasizing the need for prolonged follow-up. Among the 19 TNDM patients tested, two had paternal isodisomy of chromosome 6, seven from 4 families had paternally-derived trisomy of the 6q region, and two had a methylation defect in the 6q24 region. No chromosome 6 anomalies were found in the 9 PNDM patients tested.
Conclusion: When present, a chromosome 6 abnormality is strongly in favor of the "transient" form of the disease.