Relationship between ultrastructural lesions of glomerular filtration barrier and proteinuria in Alport syndrome

AIM: To explore the relationship between the ultrastructural lesions of glomerular filtration barrier (GFB) and proteinuria in Alport syndrome (AS). METHODS: Thirty-five AS patients (24 males and 11 females), who were admitted to our hospital from 2008 to 2012, were enrolled in this study. The median age was 6 years (1.17 ~ 24 years) according to the time of renal biopsy. The data of clinical and electron microscopic examination were collected for retrospective analysis. The patients were divided into 2 groups according to the degree of urinary protein: non-/interval proteinuria group (13 cases) and persistent proteinuria group (22 cases). The length of glomerular basement membrane(GBM) attenuation, thickening, and dense layer splitting and layering was measured, and the percentages of these lesions were calculated. The foot process width (FPW) was measured according to the formula average FPW=π／4× (∑ GBM length／∑ foot process number). The differences of the ultrastructural lesions in GFB between the 2 groups were compared, and the association between GFB ultrastructural lesions and proteinuria were analyzed. RESULTS: The percentages of GBM thickening, splitting and layering were higher, and the foot processes were wider in persistent proteinuria group than those in non-/interval proteinuria group. The median age at renal biopsy in persistent proteinuria group was older than that in non-/interval proteinuria group. The average FPW of the 35 patients was positively correlated with the percentage of GBM thickening, splitting and layering, and the age at biopsy, respectively. CONCLUSION: The severity of GBM lesions is associated with the severity of foot process damage and the severity of proteinuria, suggesting that foot process damage associated with proteinuria in AS may be secondary to GBM lesions.