FAS germline mutations have been associated with the development of autoimmune lymphoproliferative syndrome (ALPS). Occurrence of Hodgkin lymphoma (HL) has been reported in 2 families with ALPS. In both families an uncle of the index patient developed HL. A 15-year-old boy with autoimmune thrombopenia, lymphadenopathy, and splenomegaly for 6 years was studied. In an axillary lymph node biopsy nodular lymphocyte predominant (NLP) HL was diagnosed; in the areas between the nodules a proliferation of double-negative blastic T cells were present, suggestive of ALPS. Analysis for the presence of a FAS gene mutation using the denaturing gradient gel electrophoresis technique indicated a mutation in exon 9. Direct sequence analysis revealed a mutation causing a substitution of arginine with glutamine at codon 234. Because ALPS and NLP HL are both highly infrequent conditions, the occurrence in at least 3 families suggests a causative relationship between germline FAS gene mutations and NLP HL.