title: Systemic lymph node tuberculosis presenting with an aseptic psoas abscess caused by a paradoxical reaction after nine months of antituberculosis treatment: a case report.
abstract: BACKGROUND
  A paradoxical reaction during antituberculosis treatment is defined as the worsening of pre-existing tuberculosis lesions or the appearance of a new tuberculosis lesion in patients whose clinical symptoms improved with antituberculosis treatment. The median onset time to the development of a paradoxical response has been reported to be about 60 days after the start of treatment. We report the case of a patient with a paradoxical reaction presenting as a psoas abscess after nine months of antituberculosis treatment. To the best of our knowledge, this manifestation has not previously been reported.
  
  
  METHODS
  A 23-year-old Japanese man presented to our hospital with lower abdominal pain. Computed tomography showed that he had mediastinal and abdominal para-aortic lymph node swellings. Fluorine-18 fluorodeoxyglucose positron emission tomography showed hot spots in these lymph nodes and in his right cervical lymph node, suggesting a lymphoma. The examination of an abdominal lymph node biopsy specimen showed lymph node tuberculosis, so antituberculosis treatment was started. However, after nine months of treatment, he experienced right flank pain. Abdominal computed tomography showed a right psoas abscess and abdominal para-aortic lymph node swelling. The abscess was treated by percutaneous drainage. After repeated drainage, the psoas abscess subsided and disappeared. The purulent fluid yielded no microorganisms, suggesting a paradoxical reaction.
  
  
  CONCLUSIONS
  Attention should be paid to paradoxical reactions occurring during antituberculosis treatment for systemic lymph node tuberculosis.
authors.affiliation: The Third Department of Internal Medicine, Sapporo Medical University School of Medicine, Chuo-ku, South 1 West 16, Sapporo, 060-8543, Japan. gyamada@sapmed.ac.jp.
authors.forename: Gen
authors.initials: G
authors.lastname: Yamada
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Nishikiori
authors.forename: Masaru
authors.initials: M
authors.lastname: Fujii
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Inomata
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Chiba
authors.forename: Naoki
authors.initials: N
authors.lastname: Hirokawa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi