title: Early diagnosis of Danon disease: Flow cytometric detection of lysosome-associated membrane protein-2-negative leukocytes.
abstract: BACKGROUND
  Danon disease is an extremely rare X-linked dominant disorder characterized by progressive cardiomyopathy, muscle weakness, and mild mental retardation. Most cases harbor nonsense, frameshift, or splice-site mutations in LAMP2 that result in lysosome-associated membrane protein-2 (LAMP-2) deficiency and lysosomal defects. The identification of LAMP2 mutations makes it possible to detect female carriers with significant cardiomyopathy. Therefore, it is of paramount importance to develop useful carrier detection methods.
  
  
  METHODS
  To screen for diminished LAMP-2 expression among female patients with progressive cardiomyopathy, we developed a flow cytometric method to detect LAMP-2-deficient leukocytes.
  
  
  RESULTS
  In healthy controls, all circulating leukocyte populations, including granulocytes, monocytes, and lymphocytes, expressed significant levels of LAMP-2. In contrast, cells from a male patient with Danon disease lacked detectable LAMP-2. His younger twin sisters showed reduced levels of LAMP-2 expression with characteristic bimodal fluorescence intensity patterns. The percentage of LAMP-2-negative cells in the asymptomatic sibling was nearly the same as that in the symptomatic sibling.
  
  
  CONCLUSIONS
  We developed a flow cytometric assay for LAMP-2 expression that can serve as a rapid primary screening method to detect carriers of LAMP-2 deficiencies. This assay will narrow the target population before subjecting patients to more laborious and expensive gene mutation analysis.
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hashida
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Wada
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Takekatsu
authors.initials: T
authors.lastname: Saito
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan. Electronic address: kohta@staff.kanazawa-u.ac.jp.
authors.forename: Kunio
authors.initials: K
authors.lastname: Ohta
authors.affiliation: Department of Laboratory Sciences, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Kasahara
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yachie
mesh_terms: D000293:Adolescent; D002312:Cardiomyopathy, Hypertrophic / Q000097:blood / Q000175:diagnosis*; D016022:Case-Control Studies; D002648:Child; D042241:Early Diagnosis; D005260:Female; D005434:Flow Cytometry; D052120:Glycogen Storage Disease Type IIb / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D052119:Lysosomal-Associated Membrane Protein 2 / Q000378:metabolism*; D008297:Male; D010375:Pedigree
chemical_list: C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2
keywords: Danon disease; Diagnosis; Flow cytometric assay; Hypertrophic cardiomyopathy