Concomitant manifestations of systemic lupus erythematosus flare-up and nodal marginal zone B-cell lymphoma in a 41-year-old male patient: A challenging case report.

Key Clinical Message: Malignancy may be a possible cause of systemic lupus erythematosus (SLE) flare-ups, and it is necessary to consider it in the context of treatment resistance. In this case, we present a challenging instance of concomitant nodal marginal zone B-cell lymphoma (NMZL) and SLE flare-up in a 41-year-old male patient. Abstract: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that can cause various symptoms and affect multiple organs in the body. It is also associated with the development of malignancies, especially lymphomas. This case report discusses a patient who experienced a flare-up of SLE along with hypercalcemia, which led to the diagnosis of nodal marginal zone B-cell lymphoma (NMZL). This is the first case of its kind to be reported. A 41-year-old man with a 10-year history of SLE and antiphospholipid syndrome (APS) was referred to our center due to several symptoms, including fatigue, oral lesions, dyspnea, bilateral wrist pain and inflammation, mild pericardial effusion, organ enlargement, pancytopenia, high erythrocyte sedimentation (ESR) level, high anti-double stranded DNA (anti-dsDNA) level, low complement level, resistant hypercalcemia, and high brain natriuretic peptide (pro-BNP) level. After further testing, it was discovered that the patient had NMZL, which was the ultimate diagnosis. He underwent six cycles of the R-CHOP chemotherapy regimen, and his clinical and laboratory conditions improved during follow-ups. The initial case of SLE flare-up, with concomitant NMZL is being reported as the final diagnosis. In simpler terms, it is possible for lymphoma to manifest as a potential cause of SLE flare-ups, and clinicians should be mindful that they need to consider malignant conditions when faced with treatment resistance.