title: A nationwide survey of hypertrophic pachymeningitis in Japan.
abstract: OBJECTIVE
  To clarify the prevalence, frequent causes and distinct features of hypertrophic pachymeningitis (HP) according to background conditions in a nationwide survey in Japan.
  
  
  METHODS
  The study began with a preliminary survey to determine the approximate number of HP patients diagnosed from 1 January 2005 to 31 December 2009, and was followed by a questionnaire survey for clinical and laboratory findings. HP was defined as a condition with thickening of the cranial or spinal dura mater with inflammation, evidenced by MRI or histology.
  
  
  RESULTS
  Crude HP prevalence was 0.949/100 000 population. The mean age at onset was 58.3±15.8 years. Among 159 cases for whom detailed data were collated, antineutrophil cytoplasmic antibody (ANCA)-related HP was found in 54 cases (34.0%) and IgG4/multifocal fibrosclerosis (MFS)-related HP in 14 cases (8.8%). Seventy cases (44.0%) were classified as 'idiopathic' and 21 (13.2%) as 'others'. ANCA-related HP cases showed a female preponderance, a higher age of onset, and higher frequencies of otological symptoms and elevated systemic inflammatory biomarkers, but lower frequencies of diplopia compared with idiopathic HP. IgG4/MFS-related HP cases showed a marked male predominance; all had cranial HP while none had isolated spinal HP or decreased sensation.
  
  
  CONCLUSIONS
  HP is not extremely rare. ANCA-related HP is the most frequent form, followed by IgG4/MFS-related HP. Both forms have unique features, which may help to differentiate background causes.
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Yonekawa
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Murai
authors.affiliation: Department of Neurosurgery, Kitasato University School of Medicine, Sagamihara, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Utsuki
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsushita
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Masaki
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Isobe
authors.affiliation: Department of Neurological Therapeutics, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamasaki
authors.affiliation: Department of Neuropathology, Institute for Medical Science of Aging, Aichi Medical University, Nagakute, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Department of Neurology, School of Medicine, Kinki University, Osaka, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kusunoki
authors.affiliation: Department of Hygiene and Preventive Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Sakata
authors.affiliation: Department of Neurosurgery, Kitasato University School of Medicine, Sagamihara, Japan.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Fujii
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Kira
mesh_terms: D000367:Age Factors; D001921:Brain / Q000473:pathology; D003625:Data Collection; D005260:Female; D006801:Humans; D006984:Hypertrophy; D007564:Japan / Q000453:epidemiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008581:Meningitis / Q000453:epidemiology* / Q000473:pathology; D008875:Middle Aged; D059906:Neuroimaging; D049268:Positron-Emission Tomography; D015995:Prevalence; D012737:Sex Factors; D013116:Spinal Cord / Q000473:pathology; D015899:Tomography, Emission-Computed, Single-Photon
keywords: Bacteriology; Immunology; Infectious Diseases; MRI