Bilateral nephrocalcinosis in primary hyperoxaluria type 1.

A 31-year-old male presented with recurrent renal stones from the age of 12 years and renal failure secondary to nephrolithiasis on hemodialysis for the past 6 years. He had been born of a consanguineous union and one out of his five siblings also had a history of renal failure secondary to nephrolithiasis. He had moderate anemia. Abdominal X-ray showed bilateral nephrocalcinosis with multiple stones [Figure 1a, upper panel]. Axial computed tomography scan image showed bilateral cortical nephrocalcinosis, and nephrolithiasis [Figure 1b upper panel]. DNA was extracted from the peripheral blood of the patient using a standard extraction method after obtaining written informed consent. All of the 11 exons and exon-intron boundaries of AGXT gene were amplified by polymerase chain reaction (PCR) as previously described.[1] The PCR products were directly sequenced and compared to the AGXT sequence. Analysis revealed c. 33dupC mutation [Figure 1, lower panel]. Overproduction of oxalate in primary hyperoxaluria type 1 which forms insoluble calcium salts accumulates in organs including kidneys manifest as recurrent nephrolithiasis, nephrocalcinosis, or end-stage renal disease.[2] Nephrocalcinosis is characterized by the presence of calcium deposits in the renal parenchyma and may be associated with conditions such as hyperparathyroidism, medullary sponge kidney, renal papillary necrosis, renal tuberculosis, hyperoxaluria, milk-alkali syndrome, sarcoidosis, immobilization, and other conditions associated with hypercalcemia and hypercalciuria, may cause medullary nephrocalcinosis.[3] Among the 178 mutations described in the AGXT gene, Gly170Arg and c. 33dupC occur across populations at a frequency of 30% and 11%, respectively, while the Ile244Thr mutation is prevalent in North Africa and Spain.[4]

Figure 1

Upper panel – ray kidneys – ureters – bladder showed bilateral nephrocalcinosis with varying size stones within (a). Axial computed tomography scan image in bone window showed bilateral cortical nephrocalcinosis, oval – shaped calculi are seen within (b). Lower panel NA sequence chromatograms of the patient showing c. 33dupC mutation in the AGXT gene

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