title: A novel mutation in purine nucleoside phosphorylase in a child with normal uric acid levels.
abstract: BACKGROUND
  Purine nucleoside phosphorylase (PNP) deficiency is an autosomal recessive disease in which affected children present with recurrent infection and may present with failure to thrive, neurological impairment, autoimmunity, or malignancy. The diagnosis of PNP is usually suggested by a reduced level of serum uric acid. We report here a novel mutation in the nucleoside phosphorylase gene (NP gene) in a patient with primary immunodeficiency and neurological impairment but with normal uric acid levels. The diagnosis was confirmed biochemically and showed a reduced PNP activity, and also by molecular gene analysis.
  
  
  METHODS
  A case report and a complete NP gene DNA analysis.
  
  
  RESULTS
  The sequencing analysis showed a novel homozygous missense mutation, c.487T>C in the NP gene, resulting in a substitution of serine by proline at residue 163 (S163P) in the mature NP protein.
  
  
  CONCLUSIONS
  This NP missense mutation reported here is associated with recurrent infection, developmental delay, and primary immunodeficiency combined with normal uric acid levels in the affected child most likely due to a residual PNP enzyme activity. PNP deficiency causing primary immunodeficiency is still possible, even with normal uric acid levels.
authors.affiliation: Section of Allergy and Immunology, Department of Pediatrics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia. banderkh@hotmail.com
authors.forename: B
authors.initials: B
authors.lastname: Al-Saud
authors.forename: O
authors.initials: O
authors.lastname: Alsmadi
authors.forename: S
authors.initials: S
authors.lastname: Al-Muhsen
authors.forename: A
authors.initials: A
authors.lastname: Al-Ghonaium
authors.forename: H
authors.initials: H
authors.lastname: Al-Dhekri
authors.forename: R
authors.initials: R
authors.lastname: Arnaout
authors.forename: M S
authors.initials: MS
authors.lastname: Hershfield
authors.forename: H
authors.initials: H
authors.lastname: Al-Mousa
mesh_terms: D002675:Child, Preschool; D006801:Humans; D008297:Male; D009154:Mutation; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics*; D014527:Uric Acid / Q000097:blood*
chemical_list: D014527:Uric Acid; D011683:Purine-Nucleoside Phosphorylase