A case report of atypical autosomal dominant polycystic kidney disease presenting as glomerulocystic kidney superimposed with thin basement membrane nephropathy.

Abstract

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent monogenic polycystic kidney disorder, but ADPKD presented as Glomerulocystic kidney (GCK) in adults is uncommon. Thin basement membrane nephropathy (TBMN) seems to account for major causes of familial hematuria and can coexist with other glomerular diseases. Here, we report a case of atypical manifestation of ADPKD presenting as GCK superimposed with TBMN in an adult man.

Case presentation: A 40-year-old male presented with moderate proteinuria, microhematuria and renal insufficiency. He has no family history of kidney disease. Ultrasound revealed slightly enlarged kidneys with echogenic cortex. 2 to 3 visible small cortical cysts on both kidneys, and no anatomical abnormalities were detected by CT scan. Renal biopsy demonstrated that 33.3% (9/27) of the glomeruli had marked dilatation of Bowman's space. The glomerular cysts were lined by a simple layer of cuboidal epithelium, which was stained positive for Claudin-1 (parietal epithelial cell marker), but negative for LTA and DBA (tubular epithelial cell markers). There were foci of mild chronic interstitial fibrosis with few inflammatory infiltrates. Immunofluorescence stains were negative. Transmission Electron microscopy (TEM) revealed extensive glomerular basement membrane (GBM) thinning, without splitting or lamellation. The average thickness of GBM was 221 ± 25 nm. No electron dense deposits were identified by TEM. The next-generation sequencing indicated pathogenic heterozygous deletion of PKD1 exon 3, and the mutation was determined to be a de novo mutation by familial variant analysis. No pathogenic mutations of COL4A3, COL4A4, COL4A5, UMOD, TCF2 and HNF1β were identified.

Conclusion: We report a rare case of atypical ADPKD presenting as GCK superimposed with TBMN. GCK is a rare disease and often overlooked. It is important for practicing nephrologists to have a clear understanding of GCK. GCK involves in various conditions, thus genetic analysis should be considered.