RESUMO
BACKGROUND: Autoimmune encephalitis is a rare condition characterized by subacute development of cognitive and psychiatric symptoms. A paraneoplastic syndrome involves autoimmune encephalitis caused by classic antibodies. Although this condition is often associated with cancer, no malignancy has yet been found in 70-90% of patients at the time of diagnosis. CASE DESCRIPTION: We saw a 58-year-old male patient with fatigue, diarrhoea and weight loss. He was also experiencing hyperekplexia, personality changes and an instable gait. PET-CT revealed generalised lymphadenopathy. Histopathological analysis of a lymph node showed mantle cell lymphoma. Further investigation of the fluid revealed anti-DPPX IgG antibodies. We treated the patient's mantle cell lymphoma with R-CHOP; he achieved complete remission and his neurological symptoms resolved almost completely. CONCLUSION: The presence of anti-DPPX IgG antibodies is rare. Although it has not been proven that these antibodies are related to malignancies, this is the third of 30 known cases in which anti-DPPX IgG antibodies and a lymphatic malignancy were found.