Members of the Chlamydia genus of bacteria are responsible for a wide range of human diseases. Chlamydia trachomatis causes a number of sexually transmitted diseases including chlamydia, and Chlamydia pneumoniae causes acute respiratory tract infections. Both of these species have been shown to be associated with cervical cancer and lung cancer, respectively. Infection with a third species, Chlamydia psittaci, results from exposure to infected birds and possibly other animals, and it can lead to a lung infection called psittacosis. Some studies suggest that infection with C. psittaci may also be associated with other conditions such as conjunctivitis.
There are several similarities between the pathology of ocular adnexal lymphoma, a type of cancer that affects the tissue surrounding the eye, and that of gastric lymphoma, for which there is a well-established link with infection with the bacteria Helicobacter pylori. To determine whether there is an association between infection with C. trachomatis, C. pneumoniae, or C. psittaci and ocular adnexal lymphoma, Andrés J. M. Ferreri, M.D., of the San Raffaele H Scientific Institute in Milan, Italy, and colleagues examined tissue samples from 40 patients with ocular adnexal lymphoma, 26 patients with a benign condition of lymphoid tissue called lymphadenopathy, and 20 healthy people. They also collected white blood cells from 21 patients with ocular adnexal lymphoma and 38 healthy adults.
They found C. psittaci DNA in 80% (32 of 40) of the ocular adnexal lymphoma samples, in 12% (3 of 26) of the benign lymphadenopathy samples, and in none (0 of 20) of the samples from healthy people. None of the lymphoma samples contained C. trachomatis or C. pneumoniae. C. psittaci DNA was detected in the white blood cells of 43% (9 of 21) of lymphoma patients, which suggests, the authors note, that C. psittaci infection persists over time in a high proportion of patients.
Seven lymphoma patients in the study had been given antibiotics to treat C. psittaci infection. One month after treatment, there was no sign of the bacteria in any of the patients. In two of the four patients for whom clinical information was available, the lymphoma regressed after treatment with antibiotics. This observation, the authors conclude, "provides additional evidence for a role of C. psittaci infection in the development of ocular adnexal lymphomas."
In an editorial, Elaine S. Jaffe, M.D., from the National Cancer Institute, summarizes the cellular changes that lead to the development of mucosa-associated lymphoid tissue (MALT) lymphomas, a group of lymphomas that includes ocular adnexal lymphoma. She points out that MALT lymphomas are the result of immune responses gone awry and notes that the results of Dr. Ferreri and his colleagues "support the current model of MALT lymphoma pathogenesis and indicate that a multiplicity of infectious agents may ultimately be implicated as contributory factors."
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JNCI Journal of the National Cancer Institute