• Takuya Okamoto, Hisato Shima, Toshio Doi, Kandai Nozu, Tomoko Inoue, Manabu Tashiro, Seiichiro Wariishi, Hiroyasu Bando, Hiroyuki Azuma, Naohito Iwasaka, Takuji Ohara, Kazuyoshi Okada, and Jun Minakuchi.
• Department of Laboratory, Kawashima Hospital.
• Tohoku J. Exp. Med. 2023 Sep 20; 261 (1): 697369-73.

AbstractX-linked Alport syndrome is a hereditary progressive renal disease resulting from the disruption of collagen α3α4α5 (IV) heterotrimerization caused by pathogenic variants in the COL4A5 gene. This study aimed to report a male case of X-linked Alport syndrome with a mild phenotype accompanied by an atypical expression pattern of type IV collagen α5 [α5 (IV)] chain in glomerulus. A 38-year-old male presented with proteinuria (2.3 g/day) and hematuria. He has been detected urinary protein and occult blood since childhood. A renal biopsy was performed at the age of 29 years; however, a diagnosis of Alport syndrome was not considered. A renal biopsy 9 years later revealed diffuse thinning and lamellation of the glomerular basement membrane. Α staining for α5 (IV) revealed a normal expression pattern in the glomerular basement membrane and a complete negative expression in Bowman's capsule and distal tubular basement membrane. Using next-generation sequencing, we detected a COL4A5 missense variant within exon 35 (NM_000495.5: c.3088G>A, p. G1030S). The possibility of X-linked Alport syndrome should be considered when negative expression of α5 (IV) staining on Bowman's capsule was observed.

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