title: Clinical, biochemical and molecular diagnosis of a compound homozygote for the 254 bp deletion-8 bp insertion of the APRT gene suffering from severe renal failure.
abstract: OBJECTIVE
  To determine the type of mutation in a patient with clinical diagnosis of suspected APRT deficiency.
  
  
  METHODS
  A 51-year-old male patient, with a clinical history of two prior episodes of renal colic with urinary stone excretion (reported as uric acid stones in the first episode and as calcium oxalate stones in the second), was admitted to the hospital with severe non-oliguric renal failure (1.06 mmol/L serum creatinine), severe hyponatremia (114 mmol/L Na(+)), metabolic acidosis (14 mmol/L HCO(3)(-)) and uricemia in the normal range. Abnormalities at renal scan and persistency of severe renal failure required to start haemodialysis. Results of renal biopsy prompted us to undertake a biochemical and molecular biological evaluation of the patient for suspected adenine phosphoribosyltransferase (APRT) deficiency.
  
  
  RESULTS
  HPLC analysis of serum and urine, for determining purine derivative profile, showed the pathological presence of adenine in both biological fluids (3.57 micromol/L and 7.11 micromol/mmol creatinine in serum and urine, respectively; not detectable in both fluids in healthy controls). APRT assay in a sample of patient hemolysate showed no detectable activity of the enzyme (25.56+/-9.55 U/L red blood cells in control healthy subjects). Molecular biological analysis of the amplified APRT gene revealed that the patient harboured in exon 3 a homozygous 254 bp deletion-8 bp insertion, previously described only once in a compound heterozygote. Analysis of the patient family showed that heterozygotes for this APRT gene mutation, in spite of a 69% lower APRT enzymatic activity than that of healthy subjects, had no detectable adenine concentrations in both serum and urine.
  
  
  CONCLUSIONS
  Results of the first patient harbouring the homozygous 254 bp deletion-8 bp insertion of the APRT gene strongly indicated that definitive diagnosis of APRT deficiency (often under or misdiagnosed) would require a combined clinical, biochemical and molecular biological evaluation.
authors.affiliation: Institute of Biochemistry and Clinical Biochemistry, Catholic University of Rome, Rome, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Di Pietro
authors.forename: Italia
authors.initials: I
authors.lastname: Perruzza
authors.forename: Angela Maria
authors.initials: AM
authors.lastname: Amorini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Balducci
authors.forename: Lia
authors.initials: L
authors.lastname: Ceccarelli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lazzarino
authors.forename: Paola
authors.initials: P
authors.lastname: Barsotti
authors.forename: Bruno
authors.initials: B
authors.lastname: Giardina
authors.forename: Barbara
authors.initials: B
authors.lastname: Tavazzi
mesh_terms: D000225:Adenine / Q000097:blood / Q000652:urine; D000228:Adenine Phosphoribosyltransferase / Q000097:blood / Q000172:deficiency / Q000235:genetics* / Q000652:urine; D000483:Alleles; D020029:Base Pairing; D001706:Biopsy; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D005091:Exons / Q000235:genetics; D005260:Female; D006720:Homozygote; D006801:Humans; D007668:Kidney / Q000473:pathology; D008297:Male; D008875:Middle Aged; D016254:Mutagenesis, Insertional; D010375:Pedigree; D051437:Renal Insufficiency / Q000175:diagnosis* / Q000201:enzymology*; D017384:Sequence Deletion / Q000235:genetics*
chemical_list: D004247:DNA; D000228:Adenine Phosphoribosyltransferase; D000225:Adenine