Infective arthritis due to Blastocystis hominis.

Abstract

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. Abdominal examination disclosed tenderness in the lower abdomen. Rectal examination was normal. Sigmoidoscopy showed mild to moderate erythema and oedema of the rectal mucosa. Histology of the rectal mucosa was nondiagnostic, however. The haemoglobin concentration was 64 g/l with a hypochromic, microcytic blood film. The total leucocyte count was 81 -x I09 cells/l with 62% neutrophils, 36% lymphocytes, and 2% eosinophils. The erythrocyte sedimentation rate (ESR) was 150 mm in the first hour. Radiology disclosed unequivocal periarticular osteoporosis in the hands, and mild joint space narrowing of the metacarpophalangeal joints and hips bilaterally. There were marginal erosions of the proximal interphalangeal and right metacarpophalangeal joints. The rheumatoid factor, antinuclear factor, and antibodies to double stranded DNA were negative. The total serum complement level was 1-95 g/l (normal 1-22-1-66 g/l). The HIV test was negative. Joint fluid aspirated from the left knee was turbid and the leucocyte count was 38 x 109/1 with 100% neutrophils.Treatment was started with cefotaxime intravenously for presumed infectious arthritis of the knee pending results of joint fluid, blood, and stool cultures. There was no improvement after five days. Routine aerobic and anaerobic cultures of blood, synovial fluid, urine, and endocervical swab were all negative.Examination of synovial fluid (light microscopy, trichrome stain) from the left knee showed B hominis organisms. Stool specimens also disclosed large numbers of B hominis organisms (>5 per high power field). Culture for salmonella, shigella, campylobacter, and other parasites was negative.Drug treatment was switched to metronidazole 400 mg eight hourly for two weeks. The abdominal pain, diarrhoea, and left knee inflammation subsided over the next five to seven days. Repeat knee aspirate and stools were negative for B hominis. There was no recurrence of the knee inflammation at follow up four months after discharge from hospital.

Epidemiology and clinical significance of Blastocystis hominis in different population groups in Salamanca (Spain)

“…However, the clinical spectrum ofblastocytosis may be broadened in the future. In recent years several authors have detected eosinophilia in some cases of blastocystosis that disappeared following treatement (10,12,29,31) and an exceptional case of infectious arthritis due to B. hominis has been reported (19).…”

Blastocystis

“…Infection of the synovial uid has been noted to result in joint pains and swelling (Lee et al, 1990) and arthritis (Lakhanpal et al, 1991;Kruger et al, 1994).…”

Blastocystis Hominis: a Mysterious and Commonly Disregarded Parasite

“…There have been several individual cases of B. hominis infection in patients with chronic kidney disease [66,67] and arthritis [66,[68][69][70][71]. A high prevalence of the infection (95.8%) has been described in immunocompromised patients (HIV positive individuals and those with AIDS) [72].…”