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Volume 42, Number 6, December 2009

Severe diarrhea due to Isospora belli in a patient with thymoma  

Ahmad Reza Meamar, Mostafa Rezaian, Ali Zare-Mirzaei, Farzaneh Zahabiun, Amir Hossein Faghihi, Hormazd Oormazdi, Eshrat Beigom Kia

Received: October 5, 2007    Revised: June 4, 2008    Accepted: October 12, 2008   


Corresponding author:

Dr. Eshral Beigom Kia, Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, P. O. Box 14155-6446, Tehran, Iran. E-mail:


Background and purpose: 
Opportunistic isosporidial infection of the gastrointestinal tract is frequently encountered in patients with acquired immunodeficiency syndrome (AIDS) and is considered to be an AIDS-defining illness. Chronic severe watery diarrhea due to Isospora belli has also been reported in other immunodeficiency states. This report describes severe chronic debilitating diarrhea due to isosporiasis in a patient with mediastinal thymoma, a common tumor of the anterior mediastinum, originating from the epithelial cells of the thymus. Numerous oocysts of 
I. belli were detected in direct smear preparation of the diarrheic stool sample of the patient, who had an 8-month history of recurrent diarrhea. Duodenal and colonic mucosal biopsies revealed slight degrees of atrophic changes associated with infiltration of the lamina propria by an appreciable number of eosinophiles and the presence of unizoit tissue cysts of I. belli in the surface epithelium of the duodenal mucosa. The patient was first treated with trimethoprim-sulfamethoxazole and subsequently underwent complete thymectomy. Later, due to recurrence of the diarrhea, he was treated with ciprofloxacin.


Key words:

Diarrhea; Iran; Isosporiasis; Thymoma