Initial clinical manifestations in a young male with RFX6-variant-associated diabetes.

To date, heterozygous loss-of-function variants of RFX6 have been identified in 13 families with diabetes. Here, we present initial clinical information regarding a young male with diabetes who carried a heterozygous nonsense variant of RFX6 (p.Arg377Ter) previously reported in his family with diabetes. At 11 yr and 7 mo of age, the patient experienced severe thirst and hyperglycemia (331-398 mg/dL). Laboratory tests revealed elevated levels of glycated hemoglobin (HbA1c) (47 mmol/mL, 6.5%) and the Homeostatic Model for Insulin Resistance (HOMA-IR) (3.4). Blood glucose self-monitoring demonstrated grossly normal blood glucose levels, together with occasional postprandial hyperglycemia, and a few episodes of hypoglycemia. An oral glucose tolerance test revealed mild hyperglycemia and a delayed peak insulin level. His laboratory indices improved over two years with self-control of diet and exercise. These results indicate that the initial presentation of RFX6-variant-associated diabetes includes occasional hyperglycemia and hypoglycemia in response to changes in lifestyle. The possible association between RFX6 variants and mild insulin resistance requires further validation in future studies.