Аутоиммунды гемолитикалық анемия: себептері, белгілері және диагностикасы

Autoimmune hemolytic anemia (AIHA) occurs when antibodies directed against the person's own red blood cells (RBCs) cause them to burst (lyse), leading to an insufficient number of oxygen carrying red blood cells in the circulation. The lifetime of the RBCs is reduced from the normal 100–120 days to just a few days in serious cases. The intracellular components of the RBCs are released into the circulating blood and into tissues, leading to some of the characteristic symptoms of this condition. The antibodies are usually directed against high incidence antigens, therefore they also commonly act on allogenic RBCs (RBCs originating from outside the person themselves, e. g. in the case of a blood transfusion). AIHA is a relatively rare condition, with an incidence of 5–10 cases per 1 million persons per year in the warm antibody type and 0.45 to 1.9 cases per 1 million persons per year in the cold antibody type. Autoimmune hemolysis might be a precursor of later onset systemic lupus erythematosus. The terminology used in this disease is somewhat ambiguous. Although MeSH uses the term "autoimmune hemolytic anemia", some sources prefer the term "immunohemolytic anemia" so drug reactions can be included in this category. The National Cancer Institute considers "immunohemolytic anemia", "autoimmune hemolytic anemia", and "immune complex hemolytic anemia" to all be synonyms.

Symptoms of AIHA may be due to the underlying anemia; including shortness of breath or dyspnea, fatigue, headache, muscle weakness and pallor. In cold agglutinin disease (cold antibody type), agglutination and impaired passage of red blood cells through capillaries in the extremities causes acrocyanosis and Raynaud phenomenon with a rare complication of gangrene Signs of hemolysis that are present in AIHA include low hemoglobin (blood count), alterations in levels of cell markers of hemolysis; including elevated lactate dehydrogenase (LDH), decreased haptoglobin and elevated unconjugated bilirubin. Secondary AIHA can result from many other illnesses. Warm and cold type AIHA each have their own more common secondary causes. The most common causes of secondary warm type AIHA include lymphoproliferative disorders (e. g., chronic lymphocytic leukemia, lymphoma) and other autoimmune disorders (e. g., systemic lupus erythematosus, rheumatoid arthritis, scleroderma, Crohn's disease, ulcerative colitis). Less common causes of warm type AIHA include neoplasms other than lymphoid, and infection. Secondary warm type AIHA has been observed in cases of Covid 19.

AIHA can be caused by a number of different classes of antibody, with IgG and IgM antibodies being the main causative classes. Depending on which is involved, the pathology will differ. IgG is not very effective at activating complement and effectively binds the Fc receptor (FcR) of phagocytic cells, AIHA involving IgG is generally characterized by phagocytosis of RBCs. IgM is a potent activator of the classical complement pathway, thus, AIHA involving IgM is characterized by complement mediated lysis of RBCs. IgM also leads to phagocytosis of RBCs however, because phagocytic cells have receptors for the bound complement (rather than FcRs as in IgG AIHA). In general, IgG AIHA takes place in the spleen, whereas IgM AIHA takes place in Kupffer cells – phagocytic cells of the liver. Phagocytic AIHA is termed extravascular, whereas complement mediated lysis of RBCs is termed intravascular AIHA. In order for intravascular AIHA to be recognizable, it requires overwhelming complement activation, therefore most AIHA is extravascular – be it IgG or IgM mediated.

Steroids are the first line treatment in warm AIHA; with oral prednisone achieving an 80% initial response rate, with a 30 40% sustained remission rate at 1 year. Special considerations are required when treating people with AIHA using blood transfusion. In cold agglutinin disease; the patient and the extremity should be kept warm during transfusion to prevent agglutination and hemolysis of the donor and patient red blood cells.