Chlamydial infection: the link with ocular adnexal lymphomas

Some lymphoma entities are associated with chronic bacterial infections. This Review discusses the association between Chlamydophila psittaci and ocular adnexal lymphoma. Prevalence, epidemiology and detection methods of C. psittaci infection along with therapeutic implications in ocular adnexal lymphoma are also discussed. Chlamydiae are obligate intracellular bacteria that grow in eukaryotic cells and cause a wide spectrum of diseases. They can establish persistent infections, are mitogenic in vitro , promote polyclonal cell proliferation in vivo and induce resistance to apoptosis in infected cells—properties that might contribute to tumorigenesis. In fact, Chlamydophila psittaci ( Cp ) has been linked to the development and maintenance of ocular adnexal marginal zone B-cell lymphoma (OAMZL). In this indolent malignancy, Cp is transported by monocytes and macrophages and causes both local and systemic infection. Cp elementary bodies are viable and infectious in the conjunctiva and peripheral blood of patients with OAMZL. Bacterial eradication with antibiotic therapy is often followed by lymphoma regression. Despite recent advances in the understanding of this bacterium–lymphoma association, several questions remain unanswered. For instance, prevalence variations among different geographical areas and related diagnostic and therapeutic implications remain a major investigational issue. We will focus on clinical and therapeutic implications of chlamydial infections in patients with lymphomas and summarize the current knowledge on the association between Cp infection and OAMZL. Available data on the epidemiology, biology and pathogenesis of this association are analyzed and new investigative and clinical approaches are discussed. Key Points Chlamydophila psittaci ( Cp ) is the etiological agent of psittacosis in humans, a zoonotic disease caused by exposure to infected animals, mostly birds; Cp can also infect domestic mammals, including pets A potential oncogenic role is suggested for chlamydiae based on several peculiar biological properties that imply an antigen selection process during lymphoma development Cp infection prevalence varies among patients with ocular adnexal marginal zone B-cell lymphoma (OAMZL) from different geographical areas; OAMZL is usually indolent with a favorable prognosis Cp is present in monocytes and macrophages that infiltrate OAMZL as demonstrated by PCR-based techniques, immunohistochemistry, immunofluorescence and direct ele