Spectrum of Alport syndrome in an Indian cohort.

BACKGROUND

Next-generation sequencing has enabled non-invasive diagnosis of type IV collagen disease in clinical settings other than the typical presentation of Alport syndrome (AS).

METHODS

We reviewed the clinical and histological records of children diagnosed with Alport syndrome based on next-generation sequencing. Variants on clinical exome sequencing were categorized using ACMG 2015 criteria.

RESULTS

During 2015-2023, we found 43 patients (34 boys) with 39 variants in COL4A5 (n = 27), COL4A4 (n = 7), and COL4A3 (n = 5). Thirty, 8, and 5 patients had X-linked, autosomal recessive, and autosomal dominant disease, respectively. The median (IQR) age and eGFR at diagnosis were 10 (7-13) years and 100.1 (59-140) ml/min/1.73 m2, respectively. Fifteen patients were initially diagnosed with steroid-resistant nephrotic syndrome. Alport syndrome was suspected in these patients due to persistent microscopic hematuria, eGFR < 90 ml/min/1.73 m2, characteristic histology, and/or non-response to immunosuppression. Of 26 patients who underwent kidney biopsy, light microscopy revealed focal segmental glomerulosclerosis, minimal change disease, and mesangial proliferative glomerulonephritis in 9, 9, and 8 patients, respectively. Electron microscopy (n = 18) showed characteristic glomerular basement membrane changes and/or foot process effacement in 12 and 16 cases, respectively. Twenty-one patients (48.8%) had high-frequency sensorineural hearing loss, while two had lenticonus. Twelve patients progressed to chronic kidney disease stages 4-5. Median survival (IQR) with eGFR > 30 ml/min/1.73 m2 was 15.6 (13-18) years.

CONCLUSIONS

The phenotype of Alport syndrome varies from asymptomatic urinary abnormalities to hematuria, proteinuria and/or low eGFR, and steroid-resistant nephrotic syndrome. Adverse outcomes are common, especially in boys with X-linked disease.