title: [Clinical characteristics and analysis of mass spectrometric data in 33 patients with maple syrup urine disease].
abstract: OBJECTIVE
  To explore the clinical characteristics and the diagnostic method of maple syrup urine disease (MSUD).
  
  
  METHODS
  From January 2003 to December 2011, a total of 14 000 patients with suspected inherited metabolism diseases were tested. The blood levels of leucine and valine of these patients were detected by tandem mass spectrometry. The urinary level of branched-chain α-ketoacids was tested by gas chromatography-mass spectrometry. And the diagnosis was based on the elevated levels of leucine and valine in blood and branched-chain α-ketoacids in urine.
  
  
  RESULTS
  Thirty-three MSUD patients were confirmed. Their median age of initial visit was 0.17 years old (range: 7 days to 30 years old). The peak onset age of them was 2-30 days old, including 28 cases of neonatal onset (84.8%). The presenting symptoms of 28 cases were feeding difficulties (n=14), poor response, lethargy and seizures. Their median blood levels of leucine and valine (1901 (458-5804) and 600 (315-1617) µmol/L) were significantly higher than their normal levels ((50-300) and (60-250) µmol/L, both P<0.01). Their urinary levels of 2-OH-isovaleric acid, 2-keto-isovaleric acid, 2-keto-3-methylvaleric acid, 2-keto-isocaproic and acetylglycine (262.5 (5.4-624.3), 35.8 (1.9-156.0), 133.8 (7.4-611.5), 518.7 (17.2-2121.2) and 280.5 (11.0-1087.9) respectively) significantly higher than their normal levels (0, <0.1, 0, 0, <0.1 respectively, all P<0.01). In 5 intermittent MSUD patients, their blood levels of leucine and valine (402 (348-958) and 556 (322-808) µmol/L) were significantly higher than their normal levels (both P<0.01). The urinary level of 2-OH-isovaleric acid was significantly higher than its normal levels (P<0.01) while the urinary levels of other α-ketoacids were normal.
  
  
  CONCLUSIONS
  The confirmation of MSUD remains difficult because of a lack of specific clinical features. The detections of tandem mass spectrometry and gas chromatography-mass spectrometry may aid its early diagnosis.
authors.affiliation: Department of Pediatric Endocrinology, Genetic & Metabolic Diseases, Shanghai Institute of Pediatric Research, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Yang
authors.forename: Lian-shu
authors.initials: LS
authors.lastname: Han
authors.forename: Jun
authors.initials: J
authors.lastname: Ye
authors.forename: Wen-juan
authors.initials: WJ
authors.lastname: Qiu
authors.forename: Hui-wen
authors.initials: HW
authors.lastname: Zhang
authors.forename: Xiao-lan
authors.initials: XL
authors.lastname: Gao
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiao-yan
authors.initials: XY
authors.lastname: Li
authors.forename: Hao
authors.initials: H
authors.lastname: Xu
authors.forename: Xue-fan
authors.initials: XF
authors.lastname: Gu
mesh_terms: D000293:Adolescent; D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000097:blood; D002648:Child; D002675:Child, Preschool; D042241:Early Diagnosis; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007651:Keto Acids / Q000652:urine; D007930:Leucine / Q000097:blood; D008297:Male; D008375:Maple Syrup Urine Disease / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D053719:Tandem Mass Spectrometry; D014633:Valine / Q000097:blood; D055815:Young Adult
chemical_list: D000597:Amino Acids, Branched-Chain; D007651:Keto Acids; D007930:Leucine; D014633:Valine