Background The Autoimmune Lymphoproliferative Syndrome (ALPS) is an impairment of lymphocyte apoptosis expressed by generalized non-malignant lymphoproliferation, lymphadenopathy and/or splenomegaly. Majority of patients with ALPS harbor heterozygous germline mutations in the gene for the TNF receptor-family member Fas (CD 95, Apo-1) which are inherited in an autosomal dominant fashion. Somatic Fas mutations are the second most common genetic etiology of ALPS.
Case report We describe a two year old boy who was admitted with hepatosplenomegaly, generalized lymphadenopathy and anemia. Histopathological and immunohistochemical analysis of lymph nodes suggested a lymphoproliferative disorder in large granular lymphocytes. The lymphocyte phenotyping performed in the patient showed an increased population of T cells αβ double negative (LTCD3+ TCR αβ+ CD4- CD8-) about 27% (control < 2.5%). The study of FAS gene allowed the identification of a mutation in exon 9.
Conclusion ALPS is an underestimated entity that must be considered in non malign lymphoproliferation, autoimmunity and expansion of an unusual population of a/ß CD3+CD4-CD8- (double-negative T cells>1%).