Autoimmune lymphoproliferative syndrome (ALPS) is a disease of childhood characterized by typical clinical and laboratory findings. Here we describe an adult patient presenting with lymph node enlargement and splenomegaly. Pathological examination of an adenopathy supported the diagnosis of malignant T-zone lymphoma. The patient was treated accordingly. 3 years later his child was diagnosed with ALPS. Therefore the diagnosis of the father's disease was reconsidered. Review of the slides and functional tests led to the diagnosis of ALPS in both father and son. ALPS should be considered as a possible differential diagnosis in adult patients presenting with rare types of T-cell lymphomas.