Autoimmune lymphoproliferative syndrome (ALPS) is characterized clinically by chronic non-malignant lymphoproliferation and autoimmunity and is caused by a genetic defect in programmed cell death (apoptosis). Most patients with ALPS have heterozygous mutations in the Fas gene. We describe an 11-year-old Brazilian boy with hepatosplenomegaly, lymphadenopathy, hemolytic anemia, and hypergammaglobulinemia since early infancy. T cell lines from the patient were defective in Fas-mediated apoptosis. He was diagnosed as having ALPS and found to have a novel Fas gene mutation (IVS4+1G>A). In addition, he presented with glomerulonephritis in infancy. An aunt and uncle who had the same Fas mutations also had histories of glomerulonephritis. Although glomerulonephritis is common in Fas-deficient mice, it is infrequent in human ALPS. Corticosteroid therapy ameliorated the glomerulonephritis in our patient, as well as his lymphoproliferation, anemia, and hypergammaglobulinemia. This study suggests that glomerulonephritis is one of the characteristic features of ALPS.