RESUMO
BACKGROUND: Autoimmune diseases in children are rare and can be difficult to diagnose. Autoimmune lymphoproliferative syndrome (ALPS) is a well-characterized pediatric autoimmune disease caused by mutations in genes associated with the FAS-dependent apoptosis pathway. In addition, various genetic alterations are associated with the ALPS-like phenotype. OBJECTIVE: The aim of the present study was to elucidate the genetic cause of the ALPS-like phenotype. METHODS: Candidate genes associated with the ALPS-like phenotype were screened by using whole-exome sequencing. The functional effect of the identified mutations was examined by analyzing the activity of related signaling pathways. RESULTS: A de novo heterozygous frameshift mutation of TNF-α-induced protein 3 (TNFAIP3, A20), a negative regulator of the nuclear factor κB pathway, was identified in one of the patients exhibiting the ALPS-like phenotype. Increased activity of the nuclear factor κB pathway was associated with haploinsufficiency of TNFAIP3 (A20). CONCLUSION: Haploinsufficiency of TNFAIP3 (A20) by a germline heterozygous mutation leads to the ALPS phenotype.