Background.Primary immunodeficiency diseases (PIDs) are life-threatening disorders, which manifest commonly with gastrointestinal (GI) signs, mainly as chronic diarrhea. Objective. To investigate and compare infectious etiology of chronic diarrhea in different PIDs. Patients and methods. Assessing clinical features, obtaining immunological profiles, as well as characterizing infectious etiology of diarrhea were performed in 38 PID patients with chronic diarrhea. Stool samples and/or biopsy specimens were checked using culture, microscopic examination, RT-PCR, and PCR, as appropriate. The patients were diagnosed to have common variable immunodeficiency (CVID), severe combined immunodeficiency (SCID), X-linked agammaglobulinemia (XLA), and hyper-IgM (HIgM) syndrome. Results. In 32 patients we identified 41 infectious agents including 16 parasitic (39.0%, the most common Giardia lamblia), 11 bacterial (26.8%, the most common salmonella spp), 8 viral (19.5%, the most frequent group A rotavirus), and 6 fungal organisms (14.7%, the most common Candida albicans). From 6 of the patients, no infectious agent was isolated. In CVID bacteria and parasites, in SCID bacteria and viruses, in XLA parasites, and in individuals with HIgM syndrome parasites were the leading causes of chronic diarrhea. Infection with giardia and cryptosporidium were more frequent in XLA and HIgM, respectively. Conclusion. The current study suggests considering both usual and unusual pathogens in laboratory investigation and in the empiric treatment of chronic diarrhea. Opportunistic pathogens should be taken into account when no other pathogen is identified, especially in patients on long-term treatment or prophylaxis with antifungals/antibiotics and in those from geographical locations that favor pathogenicity of these organisms.
Keywords: X-linked agammaglobulinemia; common variable immunodeficiency; infection; primary immunodeficiency disease; severe combined immunodeficiency.