Clinical and genetic analysis in a patient with primary renal glucosuria: Identification of a novel mutation in the gene.

Primary renal glucosuria (PRG; OMIM #233100) is characterized by persistent glucosuria due to a reduction in the renal tubular reabsorption of glucose in the presence of a normal concentration of serum glucose and the absence of any other impairment of tubular function. The gene is the causative gene, which codes for the low-affinity sodium/glucose co-transporter SGLT2. In the present study, the case of a patient with PRG associated with a novel mutation of the gene is reported. The patient visited hospital for the evaluation of glucosuria in the absence of hyperglycemia, a condition that had been present for >20 years. The patient showed a fasting blood sugar level of 104 mg/dl, a 2-h postprandial sugar level of 101 mg/dl, a sodium level of 144 mmol/l, a potassium level of 3.7 mmol/l and a chloride level of 106 mmol/l in serum. Urine chemistry revealed that the amount of glucose excreted was 10.8 g/1.73 m/24 h; however, the levels of the other parameters were unremarkable. Polymerase chain reaction (PCR) sequencing analysis of the gene from the patient revealed a novel 1 bp deletion mutation, which altered the coding sequence of exon 10 in the transmembrane domain (c.1162delG; Ala388ProfsX48), suggesting an autosomal dominant inheritance pattern. This study identified a novel mutation in the gene related to a benign clinical characteristic and suggests that the molecular diagnosis of the gene may be useful for diagnosing renal glucosuria in patients and for deciding intervention measures for their family members.