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intestinal microsporidiosis

Tuesday 22 November 2011

Microsporidia has emerged in recent years as an opportunistic infectious agent with a ubiquitous distribution.

The clinical manifestations of this infection vary widely, from none (asymptomatic) to non-bloody watery diarrhea, abdominal cramps, weight loss, and disseminated disease, especially in immunosuppressed subjects.

This parasitological disease primarily affects immunosuppressed patients, particularly those with :
- human immunodeficiency virus (HIV)
- malignancies
- diabetes mellitus
- heart-lung, liver, and renal transplantations
- rheumatic disease patients undergoing anti-tumor necrosis factor therapy combined with disease-modifying anti-rheumatic drugs (21876969)

In addition, this infection also occurs in patients undergoing immunosuppressive drug treatment.


Microsporidia has emerged as an important cause of infectious complications in severely immunocompromised patients with HIV, recipients of solid organ transplant and patients with hematological malignancies.

Cell-mediated immunity appears to be critical for protection against microsporidia through the T helper cell 1 (Th1) cytokine response.

The importance of a Th1 response in the resistance to microsporidial infection has been demonstrated by in vitro studies showing that knockout animals for Th1 cytokines such as interferon and interleukin-12 could not clear microsporidia infections.

In fact, more severe microsporidia infections were observed in HIV-infected patients with declining CD4+ and CD8+ T-cell numbers.

Accordingly, the inhibition of TNF-alpha, a cytokine well known to be related to the Th1 response, could possibly facilitate the microsporidia infestation observed in the present study.

Moreover, experimental studies have reported a decrease in the specific protective IgG against microsporidia in animals treated with immunosuppressive drugs.

Microsporidiosis and intestinal parasitosis may present with diverse clinical manifestations, depending on the host immune status and the microsporidium species.

Diarrhea and wasting syndromes are the most common complaints; however, these parasite infections can be asymptomatic.


- Intestinal microsporidiosis: a hidden risk in rheumatic disease patients undergoing anti-tumor necrosis factor therapy combined with disease-modifying anti-rheumatic drugs? Aikawa NE, Twardowsky Ade O, Carvalho JF, Silva CA, Silva IL, Ribeiro AC, Saad CG, Moraes JC, Toledo RA, Bonfá E. Clinics (Sao Paulo). 2011;66(7):1171-5. PMID: 21876969 [Free]