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E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
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Abstract titles should be brief and reflect the content of the abstract.
Alport syndrome is an inherited kidney disease caused by pathogenic variants in COL4A3, COL4A4, or COL4A5, leading to abnormalities in type IV collagen. The typical manifestation is persistent hematuria, often accompanied by hearing loss and ocular lesions. In Japan, kidney biopsy is generally the first diagnostic approach when Alport syndrome is suspected. However, the severity of the disease varies depending on genotype and sex, and some cases cannot be diagnosed solely based on kidney histopathology. In particular, adult-onset Alport syndrome often presents with milder phenotypes. Since our institution has encountered many adult-diagnosed cases, we investigated the clinical and pathological features of genetically confirmed adult patients with Alport syndrome.
We conducted a retrospective study of 36 adult patients with pathogenic variants in type IV collagen genes and available kidney biopsy data at Toranomon Hospital and its branch. Clinical findings, family history, light microscopic findings, immunohistochemical staining for type IV collagen α chains, and electron microscopic findings were reviewed.
Among the 36 patients, two genetic types were identified: X-linked type (n=13) and autosomal dominant (AD) type (n=23). In the X-linked group, there were 8 females and 5 males, and the median age at kidney biopsy was 26 years. Hearing loss was observed in two patients, and ocular abnormalities were noted in two others. Four patients had progressed to kidney replacement therapy (KRT), with a median age of 68 years at the time of initiation. Only one case could be diagnosed based on light microscopy and immunostaining, and none were diagnosed by electron microscopy, although basement membrane thinning was identified in seven patients. The overall diagnostic yield of kidney biopsy alone in this group was therefore 7.7%. In the AD group, there were 15 females and 8 males, with a median age at biopsy of 51 years. Hearing loss was observed in three patients, and ocular abnormalities were detected in two. Five patients had reached KRT, with a median age of 40 years. One case was diagnosed based on light microscopy and immunostaining, and another was identified by electron microscopy, while basement membrane thinning was seen in 11 patients. The diagnostic yield of kidney biopsy alone in this group was 8.7%.
In adult-diagnosed Alport syndrome, the diagnostic yield of kidney biopsy is limited. Therefore, genetic testing plays an essential role in establishing a definitive diagnosis.
