Hyperoxaluria is a uncommon cause of urolithiasis.
Classification:
- hereditary / primary oxaluria
- autosomal recessive
- either inherited enzyme defect (types I and II) or intestinal hyperabsorption (type III)
- secondary hyperoxaluria
- vegetarian diet rich in oxalates
- terminal ileal disease/resecntion with increased oxalate absorption
- pyrdoxine deficiency or Aspergillus infection
Possible clinical features include:
- nephrocalcinosis
- oxalate stones
- renal failure
- cardiac manifestations - cardiomyopathy, cardiac conduction defects
- neurological manifestations - mononeuritis multiplex, peripheral neuropathy
- osteodystrophy, subcutaneous calcinosis
- synovitis
- retinal changes
Treatment options include:
- dietrary restriction of oxalate (oxalate found in chocolate, tea, beans, nuts, strawberries, rhubarb, beetroot, celary)
- ensure good fluid intake
- pyridoxine - reduces urinary oxalate excretion
- organophosphates - reduces crystal formation
- NICE have recommended that (1)
- lumasiran is recommended, within its marketing authorisation, as an option for treating primary hyperoxaluria type 1 (PH1) in people of all ages
- lumasiran is a subcutaneously administered drug based on the mechanism of RNA interference (2)
- is a synthetic double-stranded siRNA conjugated with the carbohydrate N-acetylgalactosamine (GalNAc) that targets the hydroxyacid oxidase 1 (HAO1) gene in hepatocytes
- prevents HAO1 mRNA translation to the enzyme glycolate oxidase (GO).
- GO catalyzes the conversion of glycolate to glyoxylate, which is the direct precursor of oxalate
- reduction in GO expression results in a reduction of oxalate production and an increase in glycolate levels
- transplantation in some cases - hepatic and/or renal
The precipitation of calcium oxalate stones does not seem to depend on urinary pH (in contrast to calcium phosphate stones - precipitated more favourably in alkaline urine).
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