Internal Medicine

0521779407-09 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:13

Hyperoxaluria 755

■PHII: longer survival than type I despite similar urinary oxalate excre-

tion, median onset 16 years, clinical heterogeneity (siblings with

mutations may be asymptomatic), end-stage renal disease may still

occur (12%), <30 documented cases

tests

Laboratory

■basic blood studies:

➣BUN, creatinine, Ca2+, PO4 2-, PTH may be normal or elevated

■basic urine studies:

➣urinalysis may show hematuria, calcium oxalate crystals

Screening

■elevated urine oxalate (>0.5 mmol/24 h/1.72 m2, but may be nor-

mal in impaired renal function), glycolate (>1 mmol/24 h/1.72 m2,

but may be normal in∼1/3 PHI patients) in PHI, L-glycerate

(> 0.2 mmol/24 h/1.72 m2) in PHII. NB: oxalate excretion in children

increases linearly with age and reaches adult levels at∼14 years

■elevated urine oxalate:creatinine ratio (>0.10 mmol/mmol)

■elevated blood oxalate (>30 mcM/liter), glycolate (>2500 mcM/liter)

Confirmatory Tests

■liver biopsy (PHI, PHII) or leukocytes (PHII) for enzymatic assay

■AGT immunoblotting by Western analysis (PHI)

■DNA analysis may be available in some centers (G170R and I144T

mutations account for up to 40% of mutant alleles in PHI)

Prenatal Diagnosis

■possible on chorionic villi or amniocytes by direct DNA for PHI

(genetic counseling must stress lack of genotype-phenotype corre-

lation in PHI)

■enzymatic on fetal liver for PHI

Imaging

■abdominal X-ray: calcified arteries (calcium oxalate crystals)

■renal ultrasound: nephrolithiasis

■skeletal X-rays: dense bone, ‘bone-in-bone’ phenomenon, radiolu-

cent metaphyseal bands, pathologic fractures

differential diagnosis

■causes of secondary oxalosis: renal failure from any cause, gas-

trointestinal disorders (Crohn’s disease, cystic fibrosis, pancreatic