This entity has a rapidly and acute progressive course, with pancytopenia and lung involvement and without significant lymphadenopathy, as also evidenced herein . juvenile form of systemic lupus erythematosus (SLE) is usually a rare autoimmune disorder that may affect Saikosaponin B multiple organs and systems . Of note, some primary immunodeficiencies (PIDs) are frequently associated to early-onset SLE or lupus manifestations, such as the deficiencies of the first components of the classical complement pathway and selective IgA deficiency . On the other hand, PIDs with severe antibody synthesis deficiency, such as agammaglobulinemia and common variable immunodeficiency (CVID), have been rarely associated to SLE development . CVID is usually a heterogeneous disorder with susceptibility to infections, autoimmune manifestations, and cancer  and has been classified as a predominant antibody deficiency according to the International Union of Immunological Societies (IUIS) updated classification . This PID is usually characterized by a marked decrease of two serum immunoglobulin isotypes, usually IgG and IgM and/or IgA, over two standard deviations below mean values for age, in addition to impaired ability to specific antibody production after vaccination or exposure to a known infectious agent . Autoimmune manifestations have been described in up to 20% of CVID patients . The most common autoimmune complications reported are the cytopenias, especially immune thrombocytopenic purpura, and autoimmune hepatitis . Additionally, systemic lupus erythematosus (SLE) was rarely reported in CVID patients , generally diagnosed during the disease followup. Furthermore, CVID patients have 2C8% of non-Hodgkins lymphoma, especially from B-cell origin . However, to our knowledge, CVID with T-cell lymphoma mimicking juvenile SLE (JSLE) was not described in the literature, and one RCBTB2 case was reported herein. 2. Case Report An 8-year-old female was admitted to the Pediatric Immunology Unit with a clinical history of recurrent upper respiratory infections, pneumonias, and hypogammaglobulinemia. She presented with the first severe infection when she was 6 months old, needing hospitalization in intensive care unit (ICU). At 5 and 7 years old, she had two pneumonias with pleural effusion. On admission, aged 8 years old, physical examination detected weight and height on the 25th percentile. Laboratory exams demonstrated hemoglobin 12.5?g/L, hematocrit 40.1%, white blood cell count Saikosaponin B 6500?cells/mm3, platelets 211,000/mm3, and reduced serum levels of IgG 268C497?mg/dL (normal range 952C1538?mg/dL), IgA 6?mg/dL (normal 111C335), and IgM 55C122?mg/dL (normal 59C151). Specific IgG antibodies for measles and rubella were negative despite appropriate immunization. Lymphocyte immunophenotyping showed CD3+ 2085?cells/mm3 (normal 605?2460), CD4+ 936?cells/mm3 (normal 493C1666), CD8+ 937?cells/mm3 (normal 224C1112), CD16+/56+ 233?cells/mm3 (normal 73C654), and CD19+ 69?cells/mm3 (normal 72C520). Further flow cytometry tests showed CD19+ cells ranging from 0 to 4%. Therefore, CVID was diagnosed according Saikosaponin B to IUIS criteria (decrease of at least two serum immunoglobulin isotypes and negative specific antibody production after vaccination) , and prophylactic antibiotics and intravenous immunoglobulin (IVIG) were started. Antinuclear antibody (ANA) and rheumatoid factor (RF) were negative at that moment. The treatment resulted in the maintenance of IgG 600?mg/dL and in a reduced frequency of infectious episodes. However, during the followup, she was hospitalized eight times due to septic shock (= 3), pneumonia with pleural effusion (= Saikosaponin B 2), otomastoiditis (= 1), acute cytomegalovirus infection (= 1), and urinary tract infection (= 1). At 12 years old, she developed pancytopenia [hemoglobin 10.2?g/L, hematocrit 34.2%, white blood cell count 3,790/mm3 (39% neutrophils, 54% lymphocytes, 2% eosinophils, and 5% monocytes), and platelets 108,000/mm3] associated to hepatosplenomegaly. Reticulocyte count was 1.2%, and lactate dehydrogenase (LDH) was 164?mg/dL (normal 117C213). Bone marrow aspiration was performed twice and showed hyperplasia of erythrocyte and hypoplasia of granulocyte series. At that moment, autoantibodies were not detected, such as: ANA, RF, antidouble-stranded DNA (anti-dsDNA), anti-Sm, anti-RNP, anti-Ro, anti-La, anti-P ribosomal, anticardiolipin IgG and IgM, lupus anticoagulant, anti-Scl70, anti-Jo1, anti-insulin, antineutrophil cytoplasmic (ANCA), antiglutamic acid decarboxylase (anti-GAD), antiinsulin, antithyroglobulin, antiperoxidase, antiparietal cell, antiendomysium, antismooth muscle, and anti-liver-kidney microsome antibodies. At the age of 17 years, the patient presented with fever, oral ulcers, alopecia, arthritis of wrists and elbows, headache, and cough and was hospitalized. She developed pleural and large pericardial effusion and was admitted to ICU. Laboratory exams revealed hemoglobin 7.9?g/L, hematocrit 22%, white blood cell count 1,000/mm3, platelets 17,000/mm3, reticulocyte count 0.32%, proteinuria 3.0?g/day,.