Participants with unexplained anemia, and/or thrombocytopenia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia. Clinically significant anemia, neutropenia or thrombocytopenia at screening History of autoimmune hemolytic anemia or autoimmune thrombocytopenia. Untreated autoimmunity such as autoimmune hemolytic anemia, or immune thrombocytopenia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Active and uncontrolled autoimmune hemolytic anemia (AIHA) or autoimmune thrombocytopenia (ITP) requiring daily prednisone dose of >= mg. Patients should not have active or uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia Active, uncontrolled autoimmune phenomenon (autoimmune hemolytic anemia or immune thrombocytopenia) requiring steroid therapy > mg prednisone daily or equivalent, within days of starting venetoclax Patients that have active hemolytic anemia Active, uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia requiring steroid therapy Active, uncontrolled autoimmune phenomenon (autoimmune hemolytic anemia or immune thrombocytopenia) requiring steroid therapy with > mg daily of prednisone dose or equivalent Patients that have active hemolytic anemia Active, uncontrolled autoimmune phenomenon (autoimmune hemolytic anemia or immune thrombocytopenia) requiring steroid therapy Active autoimmune disorder (with the exception of autoimmune hemolytic anemia or ITP) MRI MONITORING SUB-STUDY: Known history of severe renal insufficiency, asthma, allergic conditions, sickle cell anemia, chronic hemolytic anemia, and gastrointestinal disorders Active, uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia requiring steroid therapy Autoimmune anemia and/or thrombocytopenia poorly responsive to corticosteroids or other standard therapy No clinically apparent alternative explanation for thrombocytopenia and anemia Patients who exhibit any active or on-going autoimmune processes including, but not limited to, autoimmune hemolytic anemia or immune thrombocytopenia purpura, are NOT eligible for participation Patients with uncontrolled Autoimmune Hemolytic Anemia (AIHA) or autoimmune thrombocytopenia (ITP). Patients with active autoimmune anemia or autoimmune thrombocytopenia are NOT eligible Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Autoimmune anemia or thrombocytopenia that is poorly responsive to corticosteroids Patients that have active hemolytic anemia Known clinically significant anemia due to iron, vitamin B, or folate deficiencies, or autoimmune or hereditary hemolytic anemia, or gastrointestinal bleeding Autoimmune anemia and/or thrombocytopenia that is poorly responsive to corticosteroids or other standard therapy. Patients with uncontrolled autoimmune hemolytic anemia (AIHA) or autoimmune thrombocytopenia (ITP) Uncontrolled autoimmune hemolytic anemia or thrombocytopenia History of autoimmune hemolytic anemia or autoimmune thrombocytopenia. Untreated autoimmunity such as autoimmune hemolytic anemia, or immune thrombocytopenia Active, uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia requiring steroid therapy Uncontrolled autoimmune hemolytic anemia or thrombocytopenia History of hemolytic anemia or thalassemia Participants with uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Patients with uncontrolled autoimmune hemolytic anemia or autoimmune thrombocytopenia Patients with uncontrolled autoimmune hemolytic anemia (AIHA) or autoimmune thrombocytopenia (ITP) Patients that have active hemolytic anemia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Uncontrolled autoimmune hemolytic anemia or thrombocytopenia Uncontrolled autoimmune anemia or thrombocytopenia Suffering from an autoimmune disease (including refractory immune thrombocytopenia-ITP or refractory autoimmune hemolytic anemia-AIHA) Patients with autoimmune hemolytic anemia or autoimmune thrombocytopenia will be eligible for treatment Has autoimmune cytopenia (anemia, thrombocytopenia, leukopenia). Thrombocytopenia (<,/uL) total bilirubin ?. X institutional ULN unless due to Gilbert's syndrome, controlled autoimmune hemolytic anemia or immune thrombocytopenia Active autoimmune haemolytic anemia. Active autoimmune thrombocytopenia. Known active, uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia requiring steroid therapy Thrombocytopenia Hemolytic anemia Active hemolytic anemia Patients with sickle cell anemia and other hemolytic anemia Subjects with Gilbert's syndrome or resolving autoimmune hemolytic anemia may have a bilirubin up to . x ULN and are still eligible