Patient description: The patient is a 23-year-old man who came to the hospital with high blood pressure (175/95 mmHg) and signs of septicemia. He developed respiratory failure requiring mechanical ventilation and renal failure requiring hemodialysis. His blood smear showed microangiopathic hemolytic anemia and thrombocytopenia. His blood tests revealed elevated lactate dehydrogenase and reduced human complement C3 levels with a normal coagulation profile. He was diagnosed with atypical hemolytic uremic syndrome. He was treated with plasma exchange and corticosteroids. He has been previously vaccinated with meningococcal group ACWY conjugate vaccine and meningococcal group B vaccine. The genetic survey revealed ADAMTS13 >10%.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Chronic Lymphocytic Leukemia- Binet Staging System Adult patients with previously untreated CLL according to IWCLL (Hallek, 2018). 2. Must understand and voluntarily sign an informed consent form. 3. Age ≥ 18 years at the time of signing the informed consent form and must be able to adhere to the study visit schedule and other Protocol requirements. 4. Diagnosis of CLL prior to in the study. 5. Binet clinical stage A and Rai 0 or 1. 6. Absence of for the initiation of chemotherapy, defined by the IWCLL guidelines for diagnosis and treatment of CLL (Hallek, 2018) Evidence of progressive marrow failure as manifested by the development of, or worsening of, anemia and/or thrombocytopenia Massive (i.e. ≥6 cm below the left costal margin) or progressive or symptomatic splenomegaly Massive nodes (i.e. ≥10 cm in longest diameter) or progressive or symptomatic lymphadenopathy Progressive lymphocytosis with an increase of ≥50% over a 2-month period, or lymphocyte doubling time (LDT) of less than 6 months A minimum of any one of the following disease-related symptoms: unintentional weight loss ≥10% within the previous 6 months, significant fatigue (i.e., ECOG PS 2 or worse; cannot work or unable to perform usual activities), fevers of ≥38.0°C for 2 or more weeks without other evidence of infection, or night sweats for more than 1 month without evidence of infection Autoimmune complications including anemia or thrombocytopenia poorly responsive to corticosteroids Symptomatic or functional extranodal involvement (e.g., skin, kidney, lung, spine). 7. prognostic index with intermediate (3-5), high (6-10) or very high (11-14) risk scores. 8. Must have an Eastern Cooperative Oncology Group (ECOG) performance status score of ≤1. 9. All sexually active subjects with the capacity to reproduce (male and female) must use high-efficacy contraceptive methods during the course of the study. These restrictions apply for 3 months after the last dose of acalabrutinib. High-efficacy contraceptive methods Total abstinence when consistent with the subject's typical and preferred lifestyle (periodic abstinence [e.g. calendar methods, ovulation, symptothermal and post-ovulation methods] and the withdrawal method are not acceptable contraceptive methods) Female sterilisation defined as surgical hysterectomy, bilateral oophorectomy, or tubal ligation at least six weeks prior to the study treatment (a simple oophorectomy does not meet the definition of female sterilisation)  Prior treatment for CLL. 2. Meets any for the initiation of treatment defined by the IWCLL guidelines for diagnosis and treatment of CLL (Hallek, 2018). 3. Known Human Immunodeficiency Virus (HIV), Hepatitis B Virus (HBV) and/or Hepatitis C Virus (HCV) infection and/or known history of progressive multifocal leukoencephalopathy (PML). Subjects who are hepatitis B core antibody (anti-HBc) positive and who are surface antigen negative will need to have a negative polymerase chain reaction (PCR). Those who are hepatitis B surface antigen (HbsAg) positive or hepatitis B PCR positive will be excluded. Subjects who are hepatitis C antibody positive will need to have a negative PCR result. Those who are hepatitis C PCR positive will be excluded. 4. Estimated Glomerular Filtration Rate (Cockcroft-Gault Appendix C) ≤ 40 mL/min/1.73m2. 5. Absolute neutrophil count (ANC) < 1.0 X 109/L. 6. Platelet count < 100 X 109/L. 7. Serum aspartate aminotransferase (AST)/serum glutamic-oxaloacetic transaminase (SGOT) or alanine transaminase (ALT)/serum glutamate pyruvate transaminase (SGPT) >2.5 x upper limit of normal (ULN). 8. Serum total bilirubin >1.5 x ULN, except in cases of Gilbert's syndrome. 9. Prothrombin time/INR or aPTT (in the absence of Lupus anticoagulant) >2 x ULN. 10. Active bleeding, history of bleeding diathesis (e.g., hemophilia or von Willebrand disease). 11. Requires treatment with proton pump inhibitors (e.g., omeprazole, esomeprazole, lansoprazole, dexlansoprazole, rabeprazole, or pantoprazole). Subjects receiving proton pump inhibitors who switch to H2-receptor antagonists or antacids are eligible for enrolment to this study. 12. Unable to swallow capsules, or has disease significantly affecting gastrointestinal function that would limit absorption of oral medication. 13. Currently active, clinically significant cardiovascular disease or a history of myocardial infarction within 3 months prior to enrolment. Exception: Subjects with controlled, asymptomatic atrial fibrillation during screening can enrol on study. 14. Requires or receiving anticoagulation with warfarin or equivalent vitamin K antagonists (e.g., phenprocoumon) within 7 days of first dose of study drug. 15. Systemic infection that has not resolved prior to initiating study treatment in spite of adequate anti-infective therapy. 16. Pregnant or lactating females. 17. Participation in any clinical study or having taken any investigational therapy within 28 days prior to initiating study therapy. 18. Prior history of malignancies, other than CLL, unless the patient has been free of the disease for ≥ 3 years. Exceptions the following Basal cell carcinoma of the skin Squamous cell carcinoma of the skin Carcinoma in situ of the cervix Carcinoma in situ of the breast Incidental histologic finding of prostate cancer (TNM stage of T1a or T1b) 19. Presence of autoimmune haemolytic anaemia or autoimmune thrombocytopenia, or a positive direct antiglobulin test result. 20. Chronic use of steroids in excess of prednisone 20mg/day or its equivalent. 21. Major surgery within the last 28 days prior to registration. 22. History of stroke or intracranial hemorrhage within 6 months prior to enrolment. 23. Requires treatment with strong CYP3A4/5 Inhibitors. 24. Known history of drug-specific hypersensitivity or anaphylaxis to study drug (including active product or excipient components). 25. Any life-threatening illness, medical condition, or organ system dysfunction which, in the investigator's opinion, could compromise the subject's safety, interfere with the absorption or metabolism of acalabrutinib, or put the study outcomes at undue risk