[A monogenetic disorder instead of type 1 diabetes].

Background: Transient Neonatal Diabetes Mellitus (TNDM) is a rare monogenetic disorder characterized by impaired insulin secretion occurring in the first weeks after birth. TNDM goes into remission after a few weeks to months. However, a large number of children develop non-insulin-dependent DM during puberty.

Case Description: In this article we describe a woman who had been treated with insulin since early adulthood because of suspected type 1 diabetes (T1D). During the diagnostic process it became clear that she had been diagnosed with TNDM before. Additional genetic testing confirmed the diagnosis of 6q24-related TNDM. She successfully changed from insulin to oral (tolbutamide) treatment.

Conclusion: It is important to pay attention to personal and family history in patients with suspected DM1. Diagnosing monogenic diabetes often has clinical consequences for the index patient as well as family members.