%0 Journal Article %A Tomomi Yonekawa %A Hiroyuki Murai %A Satoshi Utsuki %A Takuya Matsushita %A Katsuhisa Masaki %A Noriko Isobe %A Ryo Yamasaki %A Mari Yoshida %A Susumu Kusunoki %A Kiyomi Sakata %A Kiyotaka Fujii %A Jun-ichi Kira %T A nationwide survey of hypertrophic pachymeningitis in Japan %D 2014 %R 10.1136/jnnp-2013-306410 %J Journal of Neurology, Neurosurgery & Psychiatry %P 732-739 %V 85 %N 7 %X Objectives 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. %U https://jnnp.bmj.com/content/jnnp/85/7/732.full.pdf