Hemolysis or haemolysis, also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid. Hemolysis may occur in vivo or in vitro.
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, life-threatening disease of the blood characterized by destruction of red blood cells by the complement system, a part of the body's innate immune system. This destructive process occurs due to deficiency of the red blood cell surface protein DAF, which normally inhibits such immune reactions. Since the complement cascade attacks the red blood cells within the blood vessels of the circulatory system, the red blood cell destruction (hemolysis) is considered an intravascular hemolytic anemia. There is ongoing research into other key features of the disease, such as the high incidence of venous blood clot formation. Research suggests that PNH thrombosis is caused by both the absence of GPI-anchored complement regulatory proteins on PNH platelets and the excessive consumption of nitric oxide (NO).
Hemolytic anemia or haemolytic anaemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells (RBCs), either in the blood vessels or elsewhere in the human body (extravascular). This most commonly occurs within the spleen, but also can occur in the reticuloendothelial system or mechanically. Hemolytic anemia accounts for 5% of all existing anemias. It has numerous possible consequences, ranging from general symptoms to life-threatening systemic effects. The general classification of hemolytic anemia is either intrinsic or extrinsic. Treatment depends on the type and cause of the hemolytic anemia.
Autoimmune hemolytic anemia (AIHA) is an autoimmune disorder which 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 circulation (anemia). 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. 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.
Paroxysmal cold hemoglobinuria (PCH) or Donath–Landsteiner hemolytic anemia (DLHA) is an autoimmune hemolytic anemia featured by complement-mediated intravascular hemolysis after cold exposure. It can present as an acute non-recurrent postinfectious event in children, or chronic relapsing episodes in adults with hematological malignancies or tertiary syphilis. Described by Julius Donath (1870–1950) and Karl Landsteiner (1868–1943) in 1904, PCH is one of the first clinical entities recognized as an autoimmune disorder.
Eculizumab, sold under the brand name Soliris among others, is a recombinant humanized monoclonal antibody used to treat paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, generalized myasthenia gravis, and neuromyelitis optica. In people with paroxysmal nocturnal hemoglobinuria, it reduces both the destruction of red blood cells and need for blood transfusion, but does not appear to affect the risk of death. Eculizumab was the first medication approved for each of its uses, and its approval was granted based on small trials. It is given by intravenous infusion. It is a humanized monoclonal antibody functioning as a terminal complement inhibitor. It binds to the complement C5 protein and inhibits activation of the complement system, a part of the body's immune system. This binding prevents the breakdown of red blood cells in the bloodstream in people with paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.
Acquired hemolytic anemia can be divided into immune and non-immune mediated forms of hemolytic anemia.
Moxetumomab pasudotox, sold under the brand name Lumoxiti, is an anti-CD22 immunotoxin medication for the treatment of adults with relapsed or refractory hairy cell leukemia (HCL) who have received at least two prior systemic therapies, including treatment with a purine nucleoside analog. Moxetumomab pasudotox is a CD22-directed cytotoxin and is the first of this type of treatment for adults with HCL. The drug consists of the binding fragment (Fv) of an anti-CD22 antibody fused to a toxin called PE38. This toxin is a 38 kDa fragment of Pseudomonas exotoxin A.
The Ham test is a blood test used in the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). Patient red blood cells (RBCs) are placed in mild acid; a positive result indicates PNH or congenital dyserythropoietic anemia. This is now an obsolete test for diagnosing PNH due to its low sensitivity and specificity.
Anifrolumab, sold under the brand name Saphnelo, is a monoclonal antibody used for the treatment of systemic lupus erythematosus. It binds to the type I interferon receptor, blocking the activity of type I interferons such as interferon-α and interferon-β.
Acalabrutinib, sold under the brand name Calquence, is a medication used to treat various types of non-Hodgkin lymphoma, including mantle cell lymphoma (MCL) and chronic lymphocytic leukemia/small lymphocytic Lymphoma (CLL/SLL). It may be used both in relapsed as well as in treatment-naive settings.
CD55deficiency, also called DAF deficiency or CHAPLE syndrome, is a rare genetic disorder of the immune system. CHAPLE stands for "CD55 deficiency with hyper-activation of complement, angiopathic thrombosis, and severe protein-losing enteropathy (PLE)." The disorder usually manifests in childhood and can be life-threatening. This condition was described by Özen, et al. in 2017.
Ravulizumab, sold under the brand name Ultomiris, is a humanized monoclonal antibody complement inhibitor medication designed for the treatment of paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome. It is designed to bind to and prevent the activation of Complement component 5 (C5).
Sutimlimab, sold under the brand name Enjaymo, is a monoclonal antibody that is used to treat adults with cold agglutinin disease (CAD). It is given by intravenous infusion. Sutimlimab prevents complement-enhanced activation of autoimmune human B cells in vitro.
Trastuzumab deruxtecan, sold under the brand name Enhertu, is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the topoisomerase I inhibitor deruxtecan. It is licensed for the treatment of breast cancer or gastric or gastroesophageal adenocarcinoma. Trastuzumab binds to and blocks signaling through epidermal growth factor receptor 2 (HER2/neu) on cancers that rely on it for growth. Additionally, once bound to HER2 receptors, the antibody is internalized by the cell, carrying the bound deruxtecan along with it, where it interferes with the cell's ability to make DNA structural changes and replicate its DNA during cell division, leading to DNA damage when the cell attempts to replicate itself, destroying the cell.
Pegcetacoplan, sold under the brand name Empaveli, among others, is a medication used to treat paroxysmal nocturnal hemoglobinuria and geographic atrophy of the retina. Pegcetacoplan is a complement inhibitor.
Iptacopan, sold under the brand name Fabhalta, is a medication used for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). It is a complement factor B inhibitor that was developed by Novartis. It is taken by mouth.
The sucrose lysis test is a diagnostic laboratory test used for diagnosing paroxysmal nocturnal hemoglobinuria (PNH), as well as for hypoplastic anemias and any hemolytic anemia with an unclear cause. The test works by using sucrose, which creates a low ionic strength environment that allows complement to bind to red blood cells. In individuals with PNH, some red blood cells are especially vulnerable to lysis caused by complement. The test may also produce suspicious results in other hematologic conditions, including megaloblastic anemia and autoimmune hemolytic anemia. False-negative results can occur when complement activity is absent in the serum. A simpler alternative called the sugar water test also involves mixing blood with sugar and observing for hemolysis, using the same principle as the sucrose lysis test.
Eplontersen, sold under the brand name Wainua, is a medication used for the treatment of transthyretin-mediated amyloidosis. It is a transthyretin-directed antisense oligonucleotide. It was developed to treat hereditary transthyretin amyloidosis by Ionis Pharmaceuticals and AstraZeneca.
Crovalimab, sold under the brand name Piasky, is a monoclonal antibody used for the treatment of people with paroxysmal nocturnal hemoglobinuria. It is a complement component 5 (C5) inhibitor.
