title: Diagnosis of Niemann-Pick disease type C with 7-ketocholesterol screening followed by NPC1/NPC2 gene mutation confirmation in Chinese patients.
abstract: BACKGROUND
  It has been reported that oxidation product of cholesterol, 7-ketocholesterol, increases in plasma of patients with NP-C. Previously, we established a rapid test to determine the plasma 7-ketocholesterol level and found it elevated significantly in patients with acid sphingomyelinase deficient NPD and NP-C disease.
  
  
  METHODS
  Individuals randomly referred to our outpatient clinics in the past two years for hepatosplenomegaly or isolated splenomegaly, who have been excluded as acid sphingomyelinase deficient NPD or Gaucher disease, and individuals with newborn cholestasis, psychomotor regression/retardation, were screened for plasma 7-ketocholesterol level. Individuals with high 7-ketocholesterol level were then analyzed for NPC1 and NPC2 gene mutation to confirm the accuracy of NP-C diagnosis.
  
  
  RESULTS
  By screening the plasma 7-ketocholesterol of suspect individuals, 12 out of 302 (4%) had shown remarkable high levels compared with reference. All these twelve individuals were subsequently confirmed to be NP-C by DNA analysis of NPC1 and NPC2 genes, with the early infantile form (n = 7), the late infantile form (n = 1), the juvenile form (n = 1) and the adult form (n = 1). Furthermore, two NP-C patients without observable neuropsychiatric disability were picked up through this procedure. Only one patient had NP-C due to NPC2 gene mutations, with the rest due to NPC1 gene mutations. We found that in NP-C patients AST was usually mildly elevated and ALT was in a normal range when jaundice was not present. In total, 22 mutant alleles were identified in the NPC1 gene, including six novel small deletions/insertions, e.g., c.416_417insC, c.1030delT, c.1800delC, c.2230_2231delGT, c.2302_2303insG, and c.2795dupA; seven novel exonic point mutations, c.1502A>T (p.D501V), c.1553G>A (p.R518Q), c.1832A>G (p.D611G), c.2054T>C (p.I685T), c.2128C>T(p.Q710X), c.2177G>C (p.R726T), c.2366G>A (p.R789H), and one novel intronic mutation c.2912-3C>G. Small deletions/insertions constituted nearly half of the mutant alleles (10/22, 45%), indicating a unique mutation spectrum in this cohort of Chinese NP-C patients.
  
  
  CONCLUSIONS
  Our data confirm in a clinical setting that screening plasma 7-ketocholesterol is an efficient and practical diagnostic tool to identify NP-C patients from suspect individuals. Patients without neuropsychological involvement could also be identified by this method therefore allowing an opportunity for earlier treatment.
authors.affiliation: Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China. huiwenzhang@yahoo.com.
authors.forename: Huiwen
authors.initials: H
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Lin
authors.forename: Rui
authors.initials: R
authors.lastname: Yang
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Qiu
authors.forename: Lianshu
authors.initials: L
authors.lastname: Han
authors.forename: Jun
authors.initials: J
authors.lastname: Ye
authors.forename: Xuefan
authors.initials: X
authors.lastname: Gu
mesh_terms: D002352:Carrier Proteins / Q000235:genetics*; D002681:China; D005260:Female; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D007223:Infant; D047908:Intracellular Signaling Peptides and Proteins; D007653:Ketocholesterols / Q000097:blood*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D009154:Mutation; D000077296:Niemann-Pick C1 Protein; D052556:Niemann-Pick Disease, Type C / Q000097:blood / Q000175:diagnosis* / Q000201:enzymology; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D007653:Ketocholesterols; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; C104585:NPC2 protein, human; D000077296:Niemann-Pick C1 Protein; D033921:Vesicular Transport Proteins; C003001:7-ketocholesterol