This article reports a patient presenting with"extremely low uric acid levels in blood and urine"clinically along with reviewing relevant literature to consider a diagnosis of xanthinuria. Peripheral blood samples of the patient and her family were further collected for xanthine dehydrogenase(XDH) gene sequencing, showing that the patient had compound heterozygous mutations in exon 19:c.1995_2006del12(p.His666_Gly669del) and exon 10:c.871G>T(p.Glu291*), however no mutations were found in the gene encoding MOCOS on chromosome 18, confirming the diagnosis of hereditary xanthinuria type Ⅰ.The patient's father, son and daughter carried heterozygous mutations in exon 19:c.1995_2006del12(p.His666_Gly669del), and the mother carried heterozygous mutations in exon 10:c.871G>T(p.Glu291*).Mutations in the XDH gene cause a lack of xanthine oxidoreductase function, which hinders the production of uric acid, leading to very low or undetectable levels in blood and urine. Patients present clinically with hematuria, renal colic, urolithiasis, and even acute renal failure. Through the diagnosis and treatment of this patient and literature review, the article aims to deepen the understanding of purine metabolism and uric acid production process, and improve the clinicians' diagnosis and treatment ability of hypouricemia. 本文报道1例以“血清和尿液尿酸水平极低”为临床表现的患者，复习相关文献考虑诊断为黄嘌呤尿症。进一步采集患者及其家系的外周血样进行黄嘌呤脱氢酶（XDH）基因测序，发现在其外显子19：c.1995_2006del12（p.His666_Gly669del）和外显子10：c.871G>T（p.Glu291*）存在复合杂合突变，而18号染色体上编码钼辅因子硫化酶基因未发现突变，确诊为遗传性Ⅰ型黄嘌呤尿症。患者父亲、儿子和女儿携带外显子19：c.1995_2006del12（p.His666_Gly669del）杂合突变，母亲携带外显子10：c.871G>T（p.Glu291*）杂合突变。XDH基因突变导致黄嘌呤氧化还原酶功能缺乏，从而阻碍了尿酸生成，使血液和尿液尿酸水平非常低或检测不到。临床可表现为血尿、肾绞痛、尿石症，甚至急性肾功能衰竭。通过本例患者的诊治和文献复习，旨在加深对嘌呤代谢及尿酸产生过程的认识，提高临床医师对低尿酸血症的诊治能力。.

Hereditary xanthinuria (HXAN) is a rare metabolic disorder that results from mutations in either the xanthine dehydrogenase (XDH) or the molybdenum cofactor sulfurase genes (MOCOS), respectively defining HXAN type I and type II. Hypouricemia, hypouricosuria, and abnormally high plasma and urine levels of xanthine, causing susceptibility to xanthine nephrolithiasis and deposition of xanthine crystals in tissues, are the metabolic hallmarks of HXAN. Several pathogenic variants in the XDH gene have so far been identified in patients with HXAN type I, but the clinical phenotype associated with the whole deletion of the human XDH gene is unknown. Herein, we report the case of a woman diagnosed with HXAN, whose molecular genetic testing revealed a homozygous microdeletion involving the XDH gene. Distinctive features of her medical history were the diagnosis of arterial hypertension and microalbuminuria at 22 years of age; a single pregnancy at the age of 25, complicated by proteinuria and transient kidney function deterioration in the third trimester; unexplained severe hypouricemia incidentally discovered during pregnancy; inability to breastfeed her newborn daughter due to primary agalactia; chronic kidney disease (CKD) stage 3 diagnosed at age 35; and progression to end-stage kidney disease over the next 12 years. Protocol noninvasive laboratory and imaging investigation was not informative as to the cause of CKD. This is the first description of the clinical phenotype associated with a natural knockout of the human XDH gene. Despite the lack of kidney histopathology data, the striking similarities with the phenotypes exhibited by comparable murine models validate the latter as useful sources of mechanistic insights for the pathogenesis of the human disease, supporting the hypothesis that the absence of xanthine dehydrogenase activity might represent a susceptibility factor for chronic tubulointerstitial nephritis, even in patients without kidney stones.

Renal calculus is a common disease with complex etiology and high recurrence rate. Recent studies have revealed that gene mutations may lead to metabolic defects which are associated with the formation of renal calculus, and single gene mutation is involved in relative high proportion of renal calculus. Gene mutations cause changes in enzyme function, metabolic pathway, ion transport, and receptor sensitivity, causing defects in oxalic acid metabolism, cystine metabolism, calcium ion metabolism, or purine metabolism, which may lead to the formation of renal calculus. The hereditary conditions associated with renal calculus include primary hyperoxaluria, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, Bartter syndrome, primary distal renal tubular acidosis, infant hypercalcemia, hereditary hypophosphatemic rickets with hypercalciuria, adenine phosphoribosyltransferase deficiency, hypoxanthine-guanine phosphoribosyltransferase deficiency, and hereditary xanthinuria. This article reviews the research progress on renal calculus associated with inborn error of metabolism, to provide reference for early screening, diagnosis, treatment, prevention and recurrence of renal calculus. 肾结石是一种病因复杂且易复发的常见疾病。人类基因组关联性研究发现多种基因突变导致的代谢缺陷与结石形成有关，其中单基因病例占比较高。基因突变引起酶功能、代谢通路、离子转运、受体敏感性等改变，导致草酸代谢、胱氨酸代谢、钙离子代谢、嘌呤代谢等缺陷，易产生遗传性肾结石。如原发性高草酸尿症、胱氨酸尿症、登特病、家族性低镁血症合并高钙尿和肾钙盐沉着症、巴特综合征、原发性远端肾小管酸中毒、婴儿高钙血症、遗传性低磷性佝偻病伴高钙尿症、腺嘌呤磷酸核糖基转移酶缺乏症、次黄嘌呤-鸟嘌呤磷酸核糖基转移酶缺乏症、遗传性黄嘌呤尿症等都与遗传性肾结石相关。本文就遗传性代谢缺陷所致肾结石的研究进展进行回顾，增加对草酸代谢、胱氨酸代谢、钙离子代谢、嘌呤代谢等缺陷致肾结石的认知，以便早期筛查、诊治及预防复发。. Renal calculus is a common disease with complex etiology and high recurrence rate. Recent studies have revealed that gene mutations may lead to metabolic defects which are associated with the formation of renal calculus, and single gene mutation is involved in relative high proportion of renal calculus. Gene mutations cause changes in enzyme function, metabolic pathway, ion transport, and receptor sensitivity, causing defects in oxalic acid metabolism, cystine metabolism, calcium ion metabolism, or purine metabolism, which may lead to the formation of renal calculus. The hereditary conditions associated with renal calculus include primary hyperoxaluria, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, Bartter syndrome, primary distal renal tubular acidosis, infant hypercalcemia, hereditary hypophosphatemic rickets with hypercalciuria, adenine phosphoribosyltransferase deficiency, hypoxanthine-guanine phosphoribosyltransferase deficiency, and hereditary xanthinuria. This article reviews the research progress on renal calculus associated with inborn error of metabolism, to provide reference for early screening, diagnosis, treatment, prevention and recurrence of renal calculus.