Absence of chlamydial infection in ocular adnexal MALT lymphoma based on next-generation sequencing

OBJECTIVES: Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) arises in various extranodal sites and has been linked to chronic inflammation, often triggered by infectious agents. Ocular adnexal (OA) MALT lymphoma has been associated with Chlamydophila psittaci (C. psittaci) in some regions. This study aimed to investigate the involvement of pathogenic microorganisms, including C. psittaci, in OA-MALT lymphoma. METHODS: DNA was extracted from 17 formalin-fixed, paraffin-embedded OA-MALT lymphoma samples. Next-generation sequencing was performed, and reads were analyzed with bioinformatic pipelines to detect non-human DNA, focusing on complete or partial genomes of known pathogenic microorganisms, including C. psittaci strain 6BC and other bacteria implicated in lymphomagenesis. RESULTS: Most sequencing reads mapped to the human genome. No complete or partial genomes of C. psittaci 6BC or other non-human pathogenic microorganisms were detected above background levels, and no consistent enrichment of microbial sequences was observed. DISCUSSION: These findings suggest that, unlike in some Western cohorts, infectious agents such as C. psittaci are unlikely to play a major etiologic role in Japanese OA-MALT lymphoma. CONCLUSION: Our analysis suggests that infectious agents, including C. psittaci, may be not associated with OA-MALT lymphoma in Japan.