T-CELL- AND ANTIBODY-MEDIATED AUTOIMMUNE MANIFESTATIONS IN SCID DUE TO IL7RA MUTATIONS

Abstract

Introduction: B+ SCID due to IL7Ra deficiency represents around 10% of SCID cases, and has seldom been described among Brazilian patients. Objective: We present two unrelated SCID female infants with IL7RA mutations and distinct autoimmune manifestations. Case 1: This infant was born to non-consanguineous parents at 28 weeks of gestational age presenting characteristic clinical as pects of Omenn syndrome (OS). She died after 2 days due to meconium-aspiration pneumonitis and pancarditis (with eosinophil and histiocyte infiltration). She presented leukocytosis (19,500/mm3), eosinophilia (4,860cells/mm3), lymphocytes=2,925cells/mm3 (CD3+=684cells/mm3, CD4+=345cells/mm3, CD8+=6cells/mm3, without naive T-cells, CD25+Foxp3+=2.3%, CD19+=641cells/mm 3, CD3-CD16+CD56+=280cells/mm3), thrombocytopenia=49,000/mm3, IgG=468mg/dL, IgM=45mg/dL, IgA<22mg/dL, IgE=3,310UI/ml. She harbored a homozygous p.C118Y IL7RA mutation. She is the second IL7Ra deficient OS in literature; the first described case presented the same mutation and was also Brazilian. Case 2: An 8-month-old girl presented since 4 months-old with severe thrombocytopenic purpura, treated with high IVIg doses and corticosteroids. She presented lymphocytopenia=1,287cells/mm3 (CD3=147cells/mm3, CD4=36cells/mm3, CD8=72cells/mm3), normal B (184cells/mm3, 80% withs IgM+IgD+) and NK numbers (259cells/mm3), very low TRECs, IgM=235mg/dL, IgA=51mg/dL, IgE=5UI/ml, and positive anti-nuclear antibodies (1/320). A sister with an equivalent clinical picture died at 15 months of age. She had compound heterozygous p.C118Y and p.I121NfsX8 IL7RA mutations. She did not present serious infections, and was successfully transplanted with cord blood cells at 13-months-old. Conclusions: Autoimmune diseases associated to “leaky” SCIDs due to IL7RA mutations may be mediated by both autoreactive T lymphocytes (probably in case1, an intrauterine OS) and autoantibodies (probably the predominant pathogenic mechanism in case2).