Typical Clinical Presentation of an Autosomal Dominant Polycystic Kidney Disease Patient with an Atypical Genetic Pattern

Background: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is mainly characterized by renal involvement with progressive bilateral development of renal cysts and volumetric increase in the kidneys, causing a loss of renal function, chronic kidney disease (CKD), and kidney failure. The occurrence of mosaicism may modulate the clinical course of the disease. Mosaicism is characterized by a few cell populations with different genomes. In these special cases, a genetic diagnosis could be challenging. Methods: Herein, we describe the case of a 47-year-old woman presenting with typical ultrasound and computed tomography features of ADPKD. She had stage 3b CKD and hypertension. There was no family history of ADPKD, prompting an investigation with a genetic test. Target next-generation sequencing (NGS) did not detect the presence of any genomic variants. Therefore, we carried out second-level genetic analysis to investigate the presence of a large rearrangement through a multiple ligation-dependent probe amplification (MLPA) analysis of PKD1 and PKD2 genes. Results: MLPA showed a large deletion (portion including exons 2–34 of PKD1) present in the heterozygosis with a percentage of cells close to the resolution limits of the technique used (