Renal hypouricemia type 2 in a patient with latent autoimmune diabetes in adults: a case report and literature review

Latent autoimmune diabetes in adults (LADA) is recognized as the most prevalent form of autoimmune diabetes in adulthood marked by a long-term preservation of endogenous insulin secretion capacity. Renal hypouricemia type 2 (RHUC2) is a rare genetic disorder characterized by defective uric acid reabsorption which results from variants in the SLC2A9 gene. Currently, there are no reported cases of RHUC2 combined with LADA. A 39-year-old servicewoman visited our hospital with the complaint of elevated blood glucose for 2 years and polydipsia, polyuria, numb right thumb for 4 months. Laboratory tests showed a high value of glucose in both urine and blood, total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), glycosylated hemoglobin (HbA1c) and anti-glutamic acid decarboxylase antibody (GADA), and a low value of fasting immunoreactive insulin (IRI) and C-peptide (C-P). She had a history of hypothyroidism for 6 years. Therefore, the patient was initially diagnosed with LADA, primary hypothyroidism and hyperlipidemia. Later, laboratory tests revealed an extremely low level of uric acid and a high value of fractional excretion of uric acid (FEUA). Two SLC2A9 heterozygous mutations, one PPP1R3A heterozygous mutation and one FOXD3 variation were found through gene analysis. Finally, the patient was diagnosed with RHUC2, LADA, Hashimoto’s thyroiditis, hyperlipidemia and antiphospholipid syndrome (APS). Two SLC2A9 heterozygous mutations, c. 227C > A and c. 1343C > T, were identified in the patient. These characteristics indicated that the patient was suffered from RHUC2.