Mutation of NPHS1, NPHS2, WT1, LAMB2, COL4A5 and other genes in children with idiopathic steroid resistant nephrotic syndrome

Background: Many children with idiopathic steroid resistant nephro�c syndrome have been reported worldwide due to muta-on of NPHS1, NPHS2, WT1 and LAMB2 genes. This study aimed to determine the frequency of muta�on of NPHS1, NPHS2, WT1, LAMB2, COL4A5 and other genes and their associa�on with renal histopathological pa�erns of idiopathic steroid resistant nephro�c syndrome pa�ents. Methods: This cross-seconal study was conducted on 25 pa�ents with idiopathic steroid resistant nephro�c aged 1-17 years in the Department of Paediatric Nephrology, Bangabandhu Sheikh Mujib Medical University, Bangladesh, from July 2017 to June 2018. Next Genera�on Sequencing and muta�on analysis were performed a�er DNA extrac�on from pa�ents' venous blood lymphocytes. Histopathological study of renal �ssue was done among 17 pa�ents. Results: A li�le more than half (56%) of the pa�ents were male. The mean age at the ini�al a�ack of nephro�c syndrome was 94.2 months. They mostly had minimal change disease (41%) and IgA nephropathy (12%). One subject had the NPHS2 gene muta�on, histopathologically diﬀuse mesangial prolifera�ve glomerulonephri�s,

An Indian study in 25 children showed NPSH2 gene mutation in 3 patients, and PLCe1, NPHS1 mutation one in each variety.All presented after their first birthday. 9Another study was conducted on a large cohort of children (n=1783) where 53.9% of them developed SRNS due to a single gene mutation. 10Thirty percent of SRNS patients who manifested before 25 years of age, a causative mutation was detected in one of the 30 different SRNS-causing genes.These findings revealed that SRNS and focal segmental glomerulosclerosis are not single disease entities but are part of a spectrum of distinct diseases with genetic etiology. 6,11 n childhood-onset SRNS, the most common mutations are found in nephrin, podocin, and WT1 encoding genes, and some studies showed LAMB2 gene mutation also.These should be screened to help clinical management and genetic counselling. 3eatments according to genetic mutation and renal histopathological pattern can avoid the adverse effects of steroids and other immunosuppressive drugs, decreasing the treatment cost.We, however, do not have these data for Bangladeshi children.This study aimed to determine the frequency of NPHS1, NPHS2, WT1, LAMB2, COL4A5 and other genes mutations and their association with renal histopathological patterns in children with SRNS.

METHODS
This cross-sectional study was conducted on 25 idiopathic SRNS patients of both sexes aged Then, mutation analysis was performed.
A renal biopsy was performed among 17 patients (whose parents agreed having a renal biopsy) for histopathological tests.

Statistical analysis
Quantitative variables were presented as mean and standard deviation.Qualitative data were expressed as numbers and percentages.because of the differences in their enrollment criteria.
Many studies, like ours, observed slight male preponderance. 13Most of our study subjects were fullterm baby.Congenital nephrotic syndrome usually happens in premature deliveries. 14Lipska et al. showed that 21% had a positive family history with sporadic steroid resistant nephrotic syndrome. 14Studies indicate that the causative recessive mutations are related to consanguinity. 6,12 nd a positive family history.But sporadic mutation in SRNS were present in some studies. 12r findings of hematuria, 15 hypertension, 16 and anemia 17 are similar to the studies worldwide.Low serum albumin, high serum cholesterol, significant proteinuria and raised serum creatinine levels 12 might have been accentuated by children's malnutrition, similar to our study.Most of the cases in our series had minimal change disease and IgA nephropathy, identical to other study findings. 12e present study observed mutations in 8% only.other study reported 6 mutations (COL4A3, COL4A4, and COL4A5 genes) in 19 patients with genetic mutations. 19Another study showed that a male SRNS patient presented at the age of 16 years with a negative family history or consanguinity, had progressive renal failure, no overt hematuria or hearing loss, FSGS on renal histopathology, and had COL4A5 gene mutation. 20

Conclusion
The frequency of identified disease-causing mutation in children older than one year with SRNS was 8%.The identified mutation was present in NPHS2 and COL4A5 genes.Minimal change disease was the major histological pattern.Children with genetic mutations had diffuse mesangial proliferative glomerulonephritis and focal segmental glomerulosclerosis in renal histopathology.NPHS2 gene mutation patient had stage -4 chronic kidney disease.

TABLE 1 Age, sex, clinical and laboratory findings of study subjects (n=25)
Sharmin MS et al.Bangabandhu Sheikh Mujib Medical University Journal 2023; https://doi.org/10.3329/bsmmuj.v16i4.66671hadpallor(TABLE1).Their mean serum albumin level was 14.5 gm/ L, serum cholesterol level was 302.9 mg/ dL, 24-hour urinary total protein was 3.9 gm/ day, and Histopathologically, 7 (41%) patients had minimal change disease, and 3 (17%) had IgA nephropathy.(FIGURE1).The initial attack of nephrotic syndrome was at the age of 66 months in a COL4A5 gene mutation patient.He had no family history of renal disease or consanguinity.Renal histopathology showed focal segmental glomerulosclerosis.He had no hematuria or pallor but was hypertensive, and e-glomerular filtration rate was 108 mL/min/1.73m 2 .DISCUSSION In this study, 25 children with idiopathic SRNS had mutations in two genes (NPHS2 and COL4A5).Minimal change disease and IgA nephropathy were the most common subtypes on histological examination.Sharmin MS et al.Bangabandhu Sheikh Mujib Medical University Journal 2023; https://doi.org/10.3329/bsmmuj.v16i4.66671Genetic mutations in children with SRNS 225

Histological subtypes of children with steroid resistant nephrotic syndrome (n=17)
Thomas et al. showed that the mean age of onset of the disease was 34.8 months. 12However, study participants' mean age and onset age are not directly comparable