The Chinese literature reported a case of stomach and duodenal MALT lymphoma complicated with gastrointestinal amyloidosis, suggesting that this type of lymphoma can cause gastrointestinal amyloid, easily misdiagnosed as duodenal ulcer and other diseases.[16] Previously literature reports two cases of thyroid MALT lymphoma with associated amyloid protein deposition.[17] With regard to our patient, we hypothesized that the secretion of IgM-Lambda monoclonal immunoglobulin in the primary thymus MALT lymphoma may lead to renal amyloidosis in the patient. The gene discussed is CD40LG; the disease is duodenal ulcer.