A Clinicopathological And Molecular Genetic Study Of Alport Syndrome In Children

Objective:The clinicopathological data and gene mutations of 133 children with Alport syndrome were analyzed,and the clinicopathological features,and gene molecular genetic characteristics were summarized.Their clinicopathological differences and correlation of genotype with phenotype were analyzed.Methods: 133 children were diagnosed with AS in the Department of Pediatric Nephropathy,Tongji Hospital affiliated to Tongji Medical College of Huazhong University of Science and Technology from j uly of 2002 to september of 2019.Their clinical pathological and follow-up data were collected,together with gene mutation screening and COL4A5 expresstion in skin.The measurement data of abnormal distribution was expressed by median(minimum to maximum)and Mann-Whitney test was used for comparison between the two groups,Kruskal-Wallis test was used for comparison among the three groups.The measurement data of normal distribution was represented by mean±standard,and analyzed by student t test.Calculators information was represented by numberand percentage,and chi-square test or Fisher exact test was used for comparison between groups.Kaplan-Mrier method was used to analyze the survival,and P<0.05 represent ed the difference had statistically meaning.Results :1.The median age of onset was 4 years old(6 months to 14.0 years)in 133 children with AS from 131 families,122 cases(91.7%)developed the disease before the age of 10.0,The ratio of male to female was 1.77:1.The average age of diagnosis was 6.6 ±3.5years.The first symp toms of 46 cases(34.6%)with AS were gross hematuria,47 cases(35.3%)presented with microscopic hematuria and proteinuria,23 cases(17.3%)with microscopic hematuria.89 cases(66.9%)(87families)were famliar and 49 cases(30.8%)(87families)are sporadic.All cases had different degrees of hematuria,96 cases(72.2%)children had proteinuria in addtion to hematuria,8 cases(6.0%)had nephrotic range proteinura.Only 3 cases(4.1%)had ocular abnormalities and 14 cases(13.5%)had hearing abnormalities among 74 examined children.65 cases(53.7%)of 121 cases showed typical changes of glomerular basement membrane.59 cases(60.8%)of 97 cases showed no or partial expression of type IV collagen α 3 / α 5 chain expression in glomerular capillary wall.Skin biopsies were performed in 42 cases,23 cases(54.8%)showed negative expression of type IV collagen α 5 chain,which was intermittently expressed in 7 cases(16.7%).2.There were 83 cases(76.1%)of XLAS,14 cases(12.8%)of ARAS and 12 cases(11.0%)of A DAS.Hematuria with proteinuria were the main manifestation among those three groups children.There was no significant difference in ratio of male to female,age of onset,family histor y,initial symptoms,ocular and hearing abnormalities,renal immunofluorescence,and typical changes of the glomerular basement membran e among those three groups.There was a significant difference in 24-hour urinary protein between male XLAS,ARAS and ADAS(P<0.05).There was a significant difference in the proportion of e GF R decrease between female XLAS and ARAS(P<0.05).3.Gene mutation screening were performed in 79 children from 77 families,52 cases(51 families)were caused by COL4A5,14 cases(14 families)were caused by COL4A4,7 cases(7 families)were caused by COL4 A3,3 cases(3 families)had digenic mution,3 cases(3 families)had unknown etiology.A total of 86 different mutation sites were detected in 76 children(74 families)with definite etiology.There were 53 mutations in COL4A5 gene,including 29 missense,4 nonsense,6 splice mutations,10 deletions,3 insertions and 1 samesense mutation.There were 21 mutations in COL4A4 gene,including 10 missense,2 nonsense,4 splice mutations,4 deletions and 1 samesense mutation.There were 12 mutations in COL4A3 gene,including 6 missense,2 splice mutations,3 deletion s and 1 insertion.XLAS were diagnosed in 54 cases(71.0%),ARAS in 11 cases(14.5%),ADAS in 11 cases(14.5%).4.There was no significant difference in onset age,family history,ocular and hearing abnormalities among XLAS children of different genders,but there were significant differences in 24-hour urinary protein,e GFR decrease and lesions of glomerular basement membrane.There was no significant difference in age of onset,initial symptoms,24-hour urinary protein quantity,eye and hearing abnormality between XLAS children with missense mutation and XLAS children with non-missense mutation,but there was a significant difference in typical changes of the glomerular basement membrane between the two groups(P < 0.05).5.91 children were followed up with an average time of 4.3 ±3.5 years.During their last follow-up,13 children developed chronic renal insufficiency,the average age was 14.3 ±1.3 years old,including 10 males and 3 females.There were 7 cases of XLAS,of which 4 cases deve loped end-stage kidney disease.There were 4 cases of ARAS had chronic renal insufficiency of which 2 cases developed end-stage kidney disease,and the mode of inheritance of the other 2 cases could not be determine d.Conclusion:1.Most children with Alport synd rome were found before the age of 10.0 years,and gross hematuria and microscopic hematuria with proteinuria were the most common symptoms,rare inially showed extrarenal manifestations.2.Electron microscop ic examination and renal tissue of type IV collagen are the most important methods in the diagnosis of children with AS.As to those atypical patients,gene testing is very helpful for early diagnosis of AS.3.Hematuria with proteinuria were the main rena l manifestations in children with different mode of inheritance.The clinical manifestations of kidney in male children with XLAS and children with ARAS(both male and female)were more severe than those with ADAS.4.COL4A5 and COL4A3 gene mutations are mainly missense and deletions,COL4A4 are mainly missense,deletions and splice mutations,and insertion mutations are rare,and the changes of glomerular basement membrane in children with XLAS with non-missense mutations were more typical than those with missense mutations.