Non-Obese Type 2 Diabetes with a History of Being an Extremely Preterm Small-for-Gestational-Age Infant without Early Adiposity Rebound

Adiposity rebound (AR), which is defined as a situation in which the body mass index (BMI) starts to increase after infancy, is a predictive marker of future development of type 2 diabetes. The patient was a 20-year-old male. He was born at 28 gestational weeks with a birthweight of 642 g (−3.20 standard deviation, small-for-gestational age [SGA]). AR during early childhood or obesity in later childhood was not observed. At the onset of type 2 diabetes (20 years of age), his BMI, body fat percentage, and body fat mass were within normal ranges (20.4, 18.4% and 10.8 kg, respectively). However, his muscle mass was 44.7 kg, with low muscle mass of the trunk and upper limbs, which was lower than the standard reference, indicating that myogenic insulin resistance was involved in the development of non-obese type 2 diabetes. This case report describes a patient with no presentation of AR and obesity during childhood, who was born extremely preterm SGA, developed non-obese type 2 diabetes with low muscle mass. We suggest that patients born extremely preterm SGA should be carefully observed for the development of type 2 diabetes, even if they did not have AR in early childhood or had not become obese.