A child with genetic FN1 mutation in the absence of classic glomerulopathy with fibronectin deposits(GFND) findings on biopsy.

Background: Glomerulopathy with fibronectin deposits (GFND) is a rare autosomal dominant genetic disorder, and proteinuria and hematuria are the most common clinical manifestations. The pathogenesis of this disease is primarily related to mutation of the fibronectin 1 gene. Unfortunately, without specific treatment, the prognosis remains poor. Here we present a case report that investigates the clinical characteristics, renal pathology, and gene testing of childhood GFND.

Case Presentation: A two-year-old child was brought to our hospital for "persistent hematuria for 1 year and 10 months." The disease onset was at the age of 4 months, with persistent microscopic hematuria accompanied by intermittent gross hematuria, occasionally with proteinuria, and without hypertension or renal failure. The chief complaint was intermittent gross hematuria, without massive proteinuria, hypertension, or renal failure. Family history: The child's mother had microscopic hematuria, his maternal aunt had nephrotic syndrome due to focal segmental glomerulosclerosis, and his maternal grandmother had end-stage renal disease. No significant pathological changes were found in the renal pathological biopsy of the child under a light microscope. Under the electron microscope, the basement membrane was found to be of uneven thickness, ranging from 150 to 400 nm. The stratum compactum of the basement membrane was thickened, with a small part showing tear-like and cobweb-like morphology. No electron-dense deposits were found. The renal tubular epithelial cells were vacuolated, and there were no unique pathological changes in the renal interstitium. Immunofluorescence showed that IgG, IgM, IgA, C3, and C1q were all negative. Alport syndrome was preliminarily considered. However, exome sequencing revealed a mutated site in the fibronectin 1 gene. The child's mother was the carrier of the pathogenic gene and the final diagnosis was GFND.

Conclusions: Fibronectin deposition is a typical pathological change in GFND, and the disease progresses slowly to end-stage renal disease. There is no specific treatment so far, and the prognosis is poor. The early onset of childhood patients may not show typical renal pathological changes, but only changes in the thickness of basement membrane, etc. Genome sequencing technology may helpful for the early diagnosis of GFND.