Pulmonary amyloidosis, gastric MALT lymphoma, and multiple sclerosis in a patient with Sjögren's disease: a case report and review of the literature.

Sjögren's disease (SjD) is a systemic autoimmune disorder associated with lymphocytic gland infiltration and an increased risk of B-cell lymphomas, particularly mucosa-associated lymphoid tissue (MALT) lymphoma. Neurological involvement may mimic multiple sclerosis (MS), while true coexistence, especially with amyloidosis, is exceptionally rare. We performed a systematic review and present a representative clinical case. A registered systematic literature review (PROSPERO CRD4201332325) was conducted according to PRISMA 2020. PubMed/MEDLINE, Scopus, the Cochrane Library, and DOAJ were searched for all records available up to July 2026. As no eligible cases were identified, additional targeted searches were performed to identify reports describing each possible combination of three of the four conditions. We also present a case report prepared according to the CARE guidelines. Among the 2,966 records identified, no studies describing the coexistence of Sjögren's disease, amyloidosis, MALT lymphoma, and MS in the same patient were found. Additional targeted searches identified 14 case reports and one case series describing Sjögren's disease with amyloidosis and MALT lymphoma, whereas no reports of Sjögren's disease with amyloidosis and MS or with MALT lymphoma and MS were identified. We therefore report the first case of Sjögren's disease complicated by pulmonary amyloidosis, gastric MALT lymphoma, and MS, highlighting the diagnostic and therapeutic challenges of this rare clinical presentation. The coexistence of Sjögren's disease, pulmonary amyloidosis, gastric MALT lymphoma, and MS is likely to be rare. Although partial associations have been reported, our literature review did not identify any previous case describing all four conditions in the same patient. This case underscores the importance of a multidisciplinary approach and suggests that possible shared immunopathogenic mechanisms warrant further investigation. Registration PROSPERO CRD4201332325.