Latent Autoimmune Diabetes in Adults Complicated by Persistent Isolated Glucosuria in the Absence of Hyperglycemia

Latent autoimmune diabetes in adults (LADA) is an autoimmune diabetes of adult-onset with the presence of diabetes associated autoantibodies. Familial renal glucosuria (FRG) is an inherited renal tubular disorder that causes persistent isolated glucosuria in the absence of hyperglycemia. We report a novel case of LADA and certain FRG. A 44-year-old man was admitted to our hospital for uncontrolled diabetes. Before admission, he had never suffered from diabetic coma and showed an improvement in HbA1c only with diet therapy. His HbA1c was 11.9% (107 mmol/mol), and anti-glutamic acid decarboxylase antibody was 13.0 U/mL. A glucagon stimulation test showed the decrease of insulin secretion: plasma C-peptide (CPR) 0 min, 0.69 ng/mL; CPR 6 min, 0.90 ng/mL. Analysis of genomic DNA revealed a novel heterozygous mutation in the SGLT2 coding gene, SLC5A2 (c.875G >A, p.Cys292Tyr), which was assessed as probably damaging with a score of 0.998 (sensitivity: 0.27; specificity: 0.99) by an in silico analysis. Therefore, he was diagnosed with LADA and certain FRG. He has not shown any symptoms and his HbA1c improved to 6.4% (46 mmol/mol) three months after the introduction of insulin therapy. Our case clearly implies the clinical effectiveness of SGLT2 inhibition in patients with LADA.