A Case of Horseshoe Kidney and Autosomal Dominant Polycystic Kidney Disease with Gene Mutation.

: Horseshoe kidney is a congenital anomaly characterized by the fusion of the kidneys at the lower pole. Polycystic kidney disease with horseshoe kidney is called polycystic horseshoe kidney. Genetic testing is essential for the diagnosis of polycystic horseshoe kidney disease because it can result from a number of genetic disorders. Fewer than 20 cases of polycystic horseshoe kidney have been reported to date. However, polycystic horseshoe kidney disease was mostly diagnosed via autopsy or radiologic imaging techniques including computed tomography, magnetic resonance imaging, and angiography. Because polycystic kidney disease has various causes, genetic testing is essential for the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) in patients with polycystic horseshoe kidney disease. At present, the diagnosis of ADPKD is made using genetic approaches, including next-generation sequencing. We reported a potentially pathogenic polycystin 1 () gene in a patient with ADPKD and horseshoe kidney. : We performed the sequencing of the gene and radiological examinations (computed abdominal tomography). : Computed abdominal tomography revealed enlarged kidneys with multiple cysts fused at the lower poles, indicating polycystic HSK. The sequencing of the gene revealed a heterozygous pathogenic variant c.165_171del (p.Leu56ArgfsTer15), which genetically confirmed the diagnosis of ADPKD. The patient was treated with an angiotensin II receptor blocker. : In this case report, we suggest that genetic testing becomes the key approach to the diagnosis of ADPKD with horseshoe kidney. Additionally, this approach offers the benefit of avoiding the possibility of the condition being mistakenly diagnosed or diagnosed late due to its uncommon occurrence and nonspecific symptoms.