Prevalence of chlamydial infection in a series of 108 primary cutaneous lymphomas

MADAM, Several infectious agents have been associated with lymphomagenesis. The identification of new causative agents allows a better understanding of pathophysiology and the development of specific treatments. Chlamydophila psittaci, the causative agent of psittacosis, is a ubiquitous, obligate intracellular bacterium that is transmitted to humans through exposure to infected reservoirs (wild and household animals). This bacterium has been linked to the development of ocular adnexal lymphomas, and bacterial eradication with doxycycline resulted in lymphoma regression in 50% of patients. Moreover, in a series of 205 consecutive cases of nodal and extranodal lymphomas, chlamydial infection has been detected in some forms of cutaneous lymphomas and in diffuse large B-cell lymphomas (DLBCL) arising in the Waldeyer’s ring, suggesting a preferential distribution of this microorganism in lymphomas occurring at extranodal organs considered as ‘first barriers’ to air-transported antigens. The limited number of cases investigated did not allow us to draw definitive conclusions, but these intriguing observations prompted us to analyse more extensively the prevalence of chlamydial infection in primary cutaneous Band T-cell lymphomas. The presence of C. psittaci infection was investigated in DNA from fresh frozen samples of skin biopsies from 108 cases of cutaneous lymphoma of four different histotypes. The samples were reviewed by one expert dermatopathologist and two haemopathologists and categorized according to the European Organisation for Research and Treatment of Cancer ⁄World Health Organization (WHO) classification: DLBCL (n = 18; including six cases of ‘leg type’ lymphoma), follicular lymphoma (n = 24), marginal zone lymphoma (MZL; n = 31) and mycosis fungoides (n = 35). Nineteen normal skin samples from surgical quadrantectomies were used as negative controls. The presence of chlamydial DNA was investigated by using three polymerase chain reaction (PCR) protocols allowing the amplification of the 16SrRNA gene and the 16S23S region: touchdown enzyme time release–PCR, outer membrane protein (ompA) and heat-shock protein 60 (hsp60). The last protocol allows the distinction between C. psittaci and other Chlamydiae (C. abortus, C. caviae, C. felis). Chlamydia trachomatis and C. pneumoniae infections were analysed by amplifying the 16S rRNA gene, and amplification of the b-globin gene was carried out as control of DNA suitability. All PCR products were analysed by agarose gel electrophoresis, fragment size quantification and direct sequencing. C. psittaci DNA sequences were found in one (5%) of the skin biopsies used as controls. Among the lymphomas, C. psittaci DNA was detected in one DLBCL (6%; Fisher exact test P = 1Æ00), in four follicular lymphomas (17%; P = 0Æ36) (Fig. 1) and in one MZL (3%; P = 1Æ00), whereas all cases of mycosis fungoides were negative (0%; P = 0Æ35). One case of follicular lymphoma was positive for C. pneumoniae. The different PCR protocols showed a good concordance, with positivity in at least two of the three PCRs in all positive cases (Table 1). This study showed that the prevalence of chlamydial infections is low in primary cutaneous lymphomas, with similar rates between DLCBL, MZL, mycosis fungoides and normal skin samples, whereas a nonsignificant trend to a higher prevalence of C. psittaci infection was observed in follicular lymphomas. This nonsignificant difference may simply be due to the relatively small subgroup size; however, the observation that C. psittaci prevalence is significantly higher in follicular lymphoma (four of 24, 17%) in comparison to all the other cutaneous lymphomas as a whole (two of 84, 2%; Fisher exact test P = 0Æ02) suggests that this association deserves to