Inherited perforin and Fas mutations in a patient with autoimmune lymphoproliferative syndrome and lymphoma

27-year-old man with the autoimmune lymphoproliferative syndrome and a large-B-cell lymphoma had heterozygous mutations in the Fas and perforin (Prf1) genes. The Fas mutation was inherited from his healthy father and was also carried by his healthy brother, whereas the Prf1 mutation was inherited from his healthy mother. The combined effect of the two mutant genes may have contributed to the development of the autoimmune lymphoproliferative syndrome and lymphoma in this patient.