Infective arthritis due to Blastocystis hominis

Ann Rheum Dis. 1990 Mar;49(3):192-3. doi: 10.1136/ard.49.3.192.


A patient with rheumatoid arthritis taking prednisone developed Blastocystis hominis acute diarrhoea, which was associated with increased inflammation and effusion of the left knee. B hominis organisms were found in synovial fluid from the left knee. The patient responded dramatically to metronidazole treatment. B hominis may become disseminated in immunosuppressed patients with diarrhoea and may cause infective arthritis.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Arthritis, Infectious / complications*
  • Arthritis, Infectious / drug therapy
  • Arthritis, Infectious / parasitology
  • Arthritis, Rheumatoid / complications*
  • Female
  • Humans
  • Intestinal Diseases, Parasitic / complications*
  • Intestinal Diseases, Parasitic / drug therapy
  • Knee Joint / parasitology
  • Metronidazole / therapeutic use
  • Protozoan Infections / complications*
  • Protozoan Infections / drug therapy
  • Protozoan Infections / parasitology
  • Synovial Fluid / parasitology


  • Metronidazole