Congenital Calcium oxalate nephropathy in a child

Oxalate nephropathy has various etiologies and remains a rare cause of renal failure. It is characterized by tubular deposition of calcium oxalate crystals due to either abnormal oxalate production or excretion. This condition can lead to acute and chronic tubular injury, interstitial fibrosis and progressive renal insufficiency. The etiologies of oxalate nephropathy are divided into primary and secondary hyperoxaluria. Primary hyperoxaluria is a rare autosomal recessive inherited metabolic disorder which leads to an increase in endogenous oxalate synthesis resulting in increased urinary oxalate excretion. Secondary hyperoxaluria is due to increased intestinal oxalate absorption, excessive dietary oxalate intake or excessive intake of oxalate precursors. Deposition of the crystals in the kidney induces renal epithelial cell injury and inflammation. The morphologic findings are the nonspecific findings of tubular atrophy and interstitial fibrosis. The distinctive feature is the presence of crystal deposition. By light microscopy, calcium oxalate crystals are gray-white and spiculated and birefringent under polarized light.We report a four-month old boy who was referred to Mofid Children’s Hospital due to high serum creatinine level which was detected during his admission to another hospital for bronchiolitis. No history of urinary symptoms or pain was given. Family history was negative. Laboratory test results were: sodium 120, potassium 4.3, blood urea nitrogen 14, creatinine 2.6, calcium 8, phosphorus 4.6, uric acid 6.9, lactate dehydrogenase 522. C3, C4, CH50, ANA and anti ds DNA were within normal limits. CBC showed hemoglobin 6, hematocrete 18.6, MCV: 67.4, MCH 21.7, MCHC 32.7, and platelet 226000. Urinalysis revealed: specific gravity: 1.010, PH: 5, WBC: 12-16/HPF, RBC: 0-1/HPF, and protein: negative. Sonography showed increased echo pattern and differentiation of both kidneys, associated with calcification of medullary papilla, which was in favor of nephrocalcinosis. He underwent open bilateral kidney biopsy which showed many intratubular crystals resembling calcium oxalate crystals, few atrophic tubules, few granular and hyaline casts and calcification in both specimens. The interstitium had mild patchy lymphocytic infiltration and fibrosis. Despite supportive therapies and correction of fluid and electrolyte abnormalities, he gradually became oliguric progressing to anuria and was put on peritoneal dialysis.This case of congenital oxalate nephropathy is reported due to its rarity.