Primary hyperoxaluria Type 1: organic aciduria diagnosed in plasma

Valongo, Carla; Rodrigues, Marilia; Dias, Aureliano; Vilarinho, Laura

http://hdl.handle.net/10400.18/4224

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Background: Primary hyperoxaluria Type 1 (PH1) is a rare autosomal recessive inborn error of glyoxylate metabolism, caused by a deficiency of the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase. The disorder results in overproduction and excessive urinary excretion of oxalate, causing recurrent urolithiasis and nephrocalcinosis. Patient and methods: The patient, a 38 year-old-woman, was referred to our lab with severe arthritis in the hips and knees, calcinosis and stage V chronic renal failure under hemodialysis. No urine samples were available to perform organic acids analysis so we studied patient plasma. Samples were extracted with ethylacetate and analyzed by GC-MS. Results: Plasmatic organic acids profile in two different samples revealed a marked excretion of oxalate (131 and 125 µmol/L; controls: 0-5) and glycolate (362 and 338 µmol/L; controls: 9-42). Glicerate concentration was normal (17 and 15 µmol/L; controls: 0-24). Conclusions: The usual biochemical indicator of PH1 is a persistently and markedly elevated urine oxalate. In the absence of urine samples, this biochemical diagnosis can also be done in plasma samples. PH1 is a treatable organic aciduria and an early and accurate diagnosis preserves renal function. So, it is important to screen for PH1 in patients with recurrent urolithiasis or unexplained renal insufficiency.