title: Acquired coccygeal nodule due to repeated stimulation by a bicycle saddle.
abstract: Four Japanese male students, aged 14, 16, 18 and 19, were found to have a nodule in their coccygeal regions. The typical lesion was a rugby-ball-shaped, normal-colored or slightly erythematous nodule measuring 5 to 6 cm in its long axis. Histopathologically, it showed hyperplasia of collagen fibers and slight acanthosis. All four students rode to school by bicycle over long distances and long periods; three of them developed the nodule after they started bicycle riding to school. We found that the nodule shape corresponded to the saddle of the bicycle. X-ray abnormalities included bending or anterior dislocation of the coccyx in all cases and spina bifida in two cases. These nodules may have developed as a result of irritation of this region by the saddle of the bicycle.
authors.affiliation: Department of Dermatology, Kumamoto University School of Medicine, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Ishihara
authors.forename: W
authors.initials: W
authors.lastname: Matsunaga
authors.forename: T
authors.initials: T
authors.lastname: Ono
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling; D002648:Child; D003050:Coccyx / Q000000981:diagnostic imaging / Q000293:injuries; D012090:Cumulative Trauma Disorders / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D011859:Radiography; D012871:Skin Diseases / Q000175:diagnosis / Q000209:etiology* / Q000601:surgery; D016135:Spinal Dysraphism / Q000150:complications / Q000000981:diagnostic imaging