INS and cystic kidney disease: In this case, the <i>HNF1B</i> score was estimated as 13 and a heterozygous variant of <i>HNF1B</i> in exon 4 (c.826C>T, p.Arg276*) was identified through Sanger sequencing.<h4>Conclusions</h4>Multiple renal cysts and youth-onset diabetes are common manifestations in patients with <i>HNF1B</i> mutations, and insufficient insulin secretion may be a potential cause of diabetic ketosis in MODY5.