title: Autoimmune aquaporin-4 myopathy in neuromyelitis optica spectrum.
abstract: OBJECTIVE
  Documentation of muscle pathology compatible with targeting of sarcolemmal aquaporin-4 (AQP4) by complement-activating IgG implies involvement of organs beyond the central nervous system in neuromyelitis optica spectrum disorders.
  
  
  METHODS
  We report on a 51-year-old woman who had relapsing optic neuritis, transverse myelitis, AQP4-IgG seropositivity, and recurrent myalgias with hyperCKemia. A muscle biopsy revealed scattered myofibers with internal nuclei, atrophy, and regeneration but no necrosis. Mild inflammatory exudates, in endomysial and perivascular spaces, consisted of lymphocytes, histiocytes, and scattered eosinophils. The sarcolemma exhibited loss of AQP4 and deposition of IgG and complement activation products, characteristics not seen in control biopsy samples of healthy muscle and immune-mediated myopathies.
  
  
  CONCLUSIONS
  Recurrent hyperCKemia accompanying AQP4-IgG seropositivity reflects targeting of skeletal muscle AQP4 by pathogenic IgG. The entity of autoimmune AQP4 myopathy extends the neuromyelitis optica spectrum beyond the central nervous system.
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Yong
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota2Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Vanda A
authors.initials: VA
authors.lastname: Lennon
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota3Department Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Bogdan F Gh
authors.initials: BF
authors.lastname: Popescu
authors.affiliation: Multiple Sclerosis Center, Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois.
authors.forename: Carrie Katherine
authors.initials: CK
authors.lastname: Grouse
authors.affiliation: Multiple Sclerosis Center, Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois.
authors.forename: Jordan
authors.initials: J
authors.lastname: Topel
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Margherita
authors.initials: M
authors.lastname: Milone
authors.affiliation: Center for Brain Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Hans
authors.initials: H
authors.lastname: Lassmann
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota2Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Parisi
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota2Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Pittock
authors.affiliation: Multiple Sclerosis Center, Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois.
authors.forename: Dusan
authors.initials: D
authors.lastname: Stefoski
authors.affiliation: Multiple Sclerosis Center, Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois.
authors.forename: Roumen
authors.initials: R
authors.lastname: Balabanov
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Claudia F
authors.initials: CF
authors.lastname: Lucchinetti
mesh_terms: D051401:Aquaporin 4 / Q000276:immunology*; D003402:Creatine Kinase / Q000097:blood; D005260:Female; D006801:Humans; D008875:Middle Aged; D009135:Muscular Diseases / Q000097:blood / Q000209:etiology / Q000276:immunology*; D009471:Neuromyelitis Optica / Q000097:blood / Q000150:complications / Q000276:immunology*
chemical_list: D051401:Aquaporin 4; D003402:Creatine Kinase