title: [A novel stop codon mutation in S gene: the molecular basis of a patient with cryptogenic cirrhosis].
abstract: OBJECTIVE
  To explore the pathogen and molecular basis of cryptogenic cirrhosis in a patient.
  
  
  METHODS
  Serum was collected from a patient, male, aged 56, with cryptogenic cirrhosis. HBV serologic markers were qualitatively tested, and HBsAg, HBeAg, and anti-HBc were quantitatively determined again. HBV DNA in serum was qualitatively tested using PCR, and quantified using fluorescence quantitative PCR. S gene was amplified, cloned, and sequenced.
  
  
  RESULTS
  HbsAg and anti-Hbe were negative, and anti-HBs, HBeAg, anti-HBc, and HBV DNA were all positive. HBsAg (S/N) was 0.77 (cutoff of S/N: >/= 2.00), HbeAg (S/N) was 56.43 (cutoff of S/N: >/= 2.10), anti-HBc (S/C(O)) was 0.03 (cutoff of S/C(O): </= 1.00); HBV DNA was 1.54 x 10(9) copies/ml. An uncommon point mutation at nucleotide 336 (C to A) in S gene was found, resulting in the change of the 61st codon into a novel stop codon and failure of synthesis of HbsAg.
  
  
  CONCLUSIONS
  HBV proves the pathogen of this case. This special mutation well explains the patient's unusual serologic pattern. Moreover, this finding possesses important clinical and theoretical significance.
authors.affiliation: Liver Diseases Research Center, Xiang ya Second Hospital, Central South University, Changsha 410011, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Yang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Lei
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hongyu
authors.initials: H
authors.lastname: Luo
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.forename: Yuhuang
authors.initials: Y
authors.lastname: Zheng
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Tang
authors.forename: Liangyou
authors.initials: L
authors.lastname: Li
mesh_terms: D001483:Base Sequence; D018388:Codon, Terminator; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics; D019694:Hepatitis B, Chronic / Q000097:blood / Q000821:virology*; D006801:Humans; D008103:Liver Cirrhosis / Q000097:blood / Q000821:virology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation
chemical_list: D018388:Codon, Terminator; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens