A Case of Secondary FSGS due to Chronic Chloride Diarrhea

Abstract

Congenital chloride diarrhea (CLD) is a rare autosomal recessive disease that is dif ficult to diagnose. CLD requires early treatment to correct electrolyte imbalance and alkalosis and to prevent severe dehydration. Renal injury is clearly associated with defective electrolyte balance induced by CLD, particularly during the first months or years of life. A 7-year-old boy was diagnosed with CLD following detec tion of a homozygous mutation (c.2063-1G>T) in SLC26A3 at 6 months of age. During treatment with electrolyte supplements, mild proteinuria was detected at 8 months of age, and is still present. Renal biopsy showed the presence of focal renal dysplasia, with metaplastic cartilage and mononuclear cell infiltration, cal­cification, and fibrosis in the interstitium. Up to two-thirds of the glomeruli exhi­bited global obsolescence, mostly aggregated in the dysplastic area. In nondysplastic areas, the glomeruli were markedly increased in size and severely hyper cellular, with increased mesangial matrix, and displayed segmental sclerosis. The marked glomerular hypertrophy with focal segmental glomerulosclerosis sug gested a compensatory reaction to the severe nephron loss or glomerular obsole scence associated with renal dysplasia, with superimposed by CLD aggravating the tubulointerstitial damage.