Colleague's E-mail is Invalid. Your message has been successfully sent to your colleague. Save my selection. Conflicts of interest: Professor Peffault de Latour received research grant from Alexion and declared consultancy and international board membership for Alexion. The other authors stated they have no relevant conflicts of interest.
The work cannot be changed in any way or used commercially without permission from the journal. Thrombosis can occur at any site, but coronary thrombosis is extremely rare. Controlled trials have demonstrated that eculizimab, an inhibitor of the terminal complement cascade, was able to reduce both hemolysis and thrombosis, but its efficacy in cases of PNH with coronary thrombosis is unknown. Thromboses, as observed in our case, may be associated with fever and marked inflammation.
This case also provides useful information on eculizumab ability to prevent further thromboembolism in PNH patients with a medical history of arterial thrombosis. Paroxysmal nocturnal hemoglobinuria PNH is a rare nonmalignant acquired clonal hematopoietic stem cell disorder that manifests with hemolytic anemia, bone marrow BM failure, and thrombosis.
In nearly all the cases of PNHan acquired somatic mutation of the X-linked PIG-A phosphatidylinositol glycan class A gene can be found, which is responsible for the expansion of hematopoietic stem cells lacking functional glycosylphosphatidylinositol GPI anchor.
This results in the deficiency of complement inhibitory proteins, leading to complement-mediated hemolysis, and also activation of monocytes, granulocytes, and platelets with formation of prothrombotic microparticles. Moreover, hemolysis with liberation of high levels of free hemoglobin leads to scavenging of nitric oxide, which contributes to platelet activation and aggregation. In PNHthrombosis can occur at any sites, the most common of which being hepatic vein Budd—Chiari syndromemesenteric and portal veins, cerebral veins, and dermal veins.
The reasons underlying the occurrence of thrombosis in these particular locations remain largely unknown. This drug has dramatically changed the natural history of PNH.
Open-label studies and case reports suggest that eculizumab also reduces the risk of further thrombotic events. We report herein the case of a patient presenting with recurrent febrile arterial coronary thromboses, despite both antiplatelet treatment and curative anticoagulation. Fever and marked inflammatory syndrome delayed both diagnosis and initiation of eculizimab, and this delay was life-threatening for the patient.
Finally, he was successfully treated with eculizumab and did no longer experience thrombotic events during the period of follow-up. A year-old male patient with a medical history of multiple thromboses 2 episodes of deep vein thrombosis in andand 2 episodes of pulmonary embolism in and presented in two consecutive acute coronary syndromes within a 1-month interval, while on continuous anticoagulation with vitamin K antagonists fluindione.
The patient was first admitted to cardiology department for acute thoracic pain in May Electrocardiogram evidenced inferior Q waves with ST elevation. Echography revealed antero-inferior akinesia.
Paroxysmal Nocturnal Hemoglobinuria (PNH)
Serum troponins were not quantified because the patient was immediately transferred for coronarography. This coronary catheterization revealed an intraluminal thrombus in the right coronary artery. Balloon angioplasty was performed, but no stent was inserted because of unexplained fever. Antiplatelet therapy with both acetylsalicylic acid and clopidogrel was added to fluidione.
A month later, the patient presented again with typical acute chest pain. Electrocardiogram always evidenced inferior Q waves with no other abnormalities.
Echography found the known antero-inferior akinesia. A new coronary catheterization was performed and again evidenced a thrombosis in the right coronary artery and a new asymptomatic incomplete intraluminal obstruction of the circumflex artery see Fig. Again, angioplasty was performed without any vascular stenting because of unexplained fever since 2 months. Because of this persistent fever and marked inflammatory syndrome, additional investigations were performed.
Clinically, the patient also presented with fatigue and signs of anemia. All tests for infectious, systemic inflammatory diseases, and vasculitis remained negative. Direct antiglobulin test was negative. A computerized tomography CT scan was performed and showed a thrombosis of the hepatic vein. Karyotype was normal.Thank you for visiting nature. You are using a browser version with limited support for CSS.
The natural history of PNH is highly variable, ranging from quiescent to life-threatening. Therapeutic strategies include terminal complement blockade and bone marrow transplantation. Eculizumab, a monoclonal antibody complement inhibitor, is highly effective and the only licensed therapy for PNH. Paroxysmal nocturnal haemoglobinuria PNH is a rare haematological disorder characterized by episodes of haemolysis, and has fascinated haematologists for more than a century because of its diverse manifestations and intricate pathophysiology 12.
The additional clinical manifestations of PNH are thrombosis, bone marrow failure and evolution of the disease to myelodysplastic syndromes. These non-erythroid manifestations indicate that PNH results from the clonal expansion of a mutated haematopoietic stem cell HSC 3 Fig. Paroxysmal nocturnal haemoglobinuria is caused by somatic mutations denoted by white stars in the X-linked PIGA gene in one or more clones of multipotent haematopoietic stem cells HSCs.
For clinical manifestations to develop, the mutated HSC clone must expand, thereby generating many affected peripheral blood cells. PIGA mutations are not sufficient to lead to clonal expansion.
Clonal expansion can arise from clonal selection by extrinsic factors for example, aplastic anaemia that preferentially target normal HSCs and, therefore, confer a conditional growth advantage to the mutated HSCs. Clonal expansion can also arise from intrinsic clonal evolution, by which HSCs acquire additional mutations that provide an intrinsic survival and growth advantage.
Both mechanisms can coexist. NK, natural killer. PowerPoint slide. The term PNH was introduced by J. Enneking in Ref. InThomas Ham observed that erythrocytes from patients with PNH haemolysed when incubated with acidified serum.
This seminal discovery resulted in the first diagnostic test for PNH: the acidified serum or Ham test 5. In the s, it was discovered that blood cells from patients with PNH are deficient in proteins that bind to the cell surface through a glycosylphosphatidylinositol GPI anchor.
Several of these proteins for example, complement decay-accelerating factor also known as CD55 and CD59 glycoprotein CD59 are complement-regulatory proteins. Indeed, a humanized monoclonal antibody that inhibits terminal complement activation eculizumab; manufactured with the brand name Soliris by Alexion Pharmaceuticals, New Haven, Connecticut, USA can ameliorate haemolysis and disease symptoms in patients with PNH 6.
Clonal cells with a deficiency of GPI-anchored proteins can be erythrocytes, platelets, polymorphonuclear leukocytes, monocytes and B cell, T cell and natural killer lymphocytes 78.
However, because erythrocytes lack a nucleus, they are more susceptible to lysis. Mutations in the phosphatidylinositol glycan anchor biosynthesis class A gene PIGAwhich encodes a protein essential for the synthesis of GPI anchors, are responsible for the GPI-anchored protein deficiency 9. This Primer covers the epidemiology, pathophysiology, clinical manifestations, diagnosis and management of PNH.
PNH incidence is estimated at 1—1. The disease occurs more frequently in countries in Asia for example, Japan, Korea and China than in western countries the United States, Spain and the United Kingdom 10 The International PNH Registry was established in to collect comprehensive data on the natural history of PNH and can provide some epidemiology data As of 30 June1, patients from centres in 25 countries were enrolled; of these patients, No definitive biological data exist to fully explain this distribution; furthermore, there may be bias in the registry.
The most prominently represented age range was 30—59 years PNH is rare in children; it tends to manifest in the teenage years 14 — There is a slight female predominance Paroxysmal nocturnal hemoglobinuria is an acquired disorder that leads to the premature death and impaired production of blood cells.
The disorder affects red blood cells erythrocyteswhich carry oxygen; white blood cells leukocyteswhich protect the body from infection; and platelets thrombocyteswhich are involved in blood clotting.
Paroxysmal nocturnal hemoglobinuria affects both sexes equally, and can occur at any age, although it is most often diagnosed in young adulthood. People with paroxysmal nocturnal hemoglobinuria have sudden, recurring episodes of symptoms paroxysmal symptomswhich may be triggered by stresses on the body, such as infections or physical exertion.
During these episodes, red blood cells are prematurely destroyed hemolysis. Affected individuals may pass dark-colored urine due to the presence of hemoglobin, the oxygen-carrying protein in blood. The abnormal presence of hemoglobin in the urine is called hemoglobinuria.
In many, but not all cases, hemoglobinuria is most noticeable in the morning, upon passing urine that has accumulated in the bladder during the night nocturnal. The premature destruction of red blood cells results in a deficiency of these cells in the blood hemolytic anemiawhich can cause signs and symptoms such as fatigue, weakness, abnormally pale skin pallorshortness of breath, and an increased heart rate.
People with paroxysmal nocturnal hemoglobinuria may also be prone to infections due to a deficiency of white blood cells. Abnormal platelets associated with paroxysmal nocturnal hemoglobinuria can cause problems in the blood clotting process.
As a result, people with this disorder may experience abnormal blood clotting thrombosisespecially in large abdominal veins; or, less often, episodes of severe bleeding hemorrhage. Individuals with paroxysmal nocturnal hemoglobinuria are at increased risk of developing cancer in blood-forming cells leukemia. In some cases, people who have been treated for another blood disease called aplastic anemia may develop paroxysmal nocturnal hemoglobinuria. Paroxysmal nocturnal hemoglobinuria is a rare disorder, estimated to affect between 1 and 5 per million people.
Mutations in the PIGA gene cause paroxysmal nocturnal hemoglobinuria. This protein takes part in a series of steps that produce a molecule called GPI anchor. GPI anchor attaches many different proteins to the cell membrane, thereby ensuring that these proteins are available when needed at the surface of the cell.
Some gene mutations are acquired during a person's lifetime and are present only in certain cells. These changes, which are called somatic mutations, are not inherited. In people with paroxysmal nocturnal hemoglobinuriasomatic mutations of the PIGA gene occur in blood-forming cells called hematopoietic stem cells, which are found mainly in the bone marrow.
These mutations result in the production of abnormal blood cells. As the abnormal hematopoietic stem cells multiply, increasing numbers of abnormal blood cells are formed, alongside normal blood cells produced by normal hematopoietic stem cells. The premature destruction of red blood cells seen in paroxysmal nocturnal hemoglobinuria is caused by a component of the immune system called complement.
Complement consists of a group of proteins that work together to destroy foreign invaders such as bacteria and viruses.Robert A. Brodsky; Paroxysmal nocturnal hemoglobinuria. Blood ; 18 : — Paroxysmal nocturnal hemoglobinuria PNH is a rare bone marrow failure disorder that manifests with hemolytic anemia, thrombosis, and peripheral blood cytopenias.
The absence of two glycosylphosphatidylinositol GPI -anchored proteins, CD55 and CD59, leads to uncontrolled complement activation that accounts for hemolysis and other PNH manifestations.
GPI anchor protein deficiency is almost always due to somatic mutations in phosphatidylinositol glycan class A PIGAa gene involved in the first step of GPI anchor biosynthesis; however, alternative mutations that cause PNH have recently been discovered.
In addition, hypomorphic germ-line PIGA mutations that do not cause PNH have been shown to be responsible for a condition known as multiple congenital anomalies-hypotonia-seizures syndrome 2.
Eculizumab, a first-in-class monoclonal antibody that inhibits terminal complement, is the treatment of choice for patients with severe manifestations of PNH. Bone marrow transplantation remains the only cure for PNH but should be reserved for patients with suboptimal response to eculizumab. Paroxysmal nocturnal hemoglobinuria PNH is a clonal hematopoietic stem cell disorder that manifests with hemolytic anemia, bone marrow failure, and thrombosis.
Later reports by Marchiafava and Micheli led to the eponym, Marchiafava-Micheli syndrome, but it was Enneking, inwho introduced the term paroxysmal nocturnal hemoglobinuria. The cell lysis following acidified serum appeared to be complement dependent because heat inactivation abrogated the reaction; however, it was not untilwith the discovery of the alternative pathway of complement activation, that complement was formally proven to cause the hemolysis of PNH red cells.
In the s, it was discovered that PNH cells display a global deficiency in a group of proteins affixed to the cell surface by a glycosylphosphatidylinositol GPI anchor. Hemolysis in PNH is complement mediated and is a direct result of PNH cells acquiring a deficiency of complement regulatory proteins.
This results in the deficiency of complement inhibitory proteins CD55 and CD59 that leads to chronic complement-mediated hemolysis of the GPI-deficient erythrocytes, as well as activation of platelets, monocytes, and granulocytes. Central to these mechanisms is the alternative pathway of complement activation. In this pathway, C3 protein spontaneously hydrolyzes and leads to the formation of C3 convertase this process is also known as tick-over.
Hemolysis in PNH is chronic because of a continuous state of complement activation through tick-over, but paroxysms resulting in brisk hemolysis coincide with increases in complement activation triggered by surgery, infection, or inflammation. The mechanism of intravascular hemolysis begins with the increased activity of C3 convertases on the surface of PNH erythrocytes as a result of the lack of CD This leads to activation of C3, C5, and the terminal pathway of complement culminating in the formation of the MAC.
This is the result of the lack of CD Opsonized erythrocytes are cleared and destroyed by cells of the reticulo-endothelial system. However, extravascular hemolysis can become the primary mechanism of hemolysis in patients treated with the terminal complement inhibitor, eculizumab Figure 2. GPI anchor biosynthesis.
A Core structure of the GPI anchor. The inositol-phospholipid PI is anchors into the lipid bilayer of the plasma membrane. The glycan core consists of a molecule of N -glucosamine, 3 manose molecules Manand a molecule of ethanolamine phosphate.
The protein is covalently attached through an amide bond to an ethanolamine on the terminal mannose. B GPI anchor biosynthesis takes place in the endoplasmic reticulum. After the protein is attached to the GPI anchor, the mature GPI-anchored protein goes to the Golgi, where fatty acid remodeling occurs and C eventually the GPI anchored protein is transported to the plasma membrane.Paroxysmal nocturnal hemoglobinuria PNH is a disease characterized by chronic persistent hemolysis, multi-organ damage and eventually multiple organ failure.
PNH develops as a result of increased sensitivity to complement due to an acquired deficiency of certain glycosylphosphatidylinositol GPI -linked proteins.
The clinical presentation of PNH varies greatly from one patient to another. We present three cases of PNH with different clinical presentations to illustrate the debilitating nature of the disease, possible fatal outcomes, and the need to timely diagnosis and targeted therapy. These cases also underline the need for increased awareness of PNH among relevant healthcare specialties. PNH should be considered as a differential diagnosis in patients with unexplained abdominal pain, dyspnea, renal failure, thrombosis and non-immune hemolytic anemia.
Paroxysmal nocturnal hemoglobinuria PNH is a chronic hemolytic disease characterized by a mutation in the phosphatidylinositol glycan class A PIG-A gene that results in the partial or complete absence of certain glycosylphosphatidylinositol GPI -linked proteins [ 1 ]. This mutation results in uncontrolled complement-mediated hemolysis and platelet activation due to the absence of CD55 DAF: decay accelerating factor and CD59 MIRL; membrane inhibitor of reactive lysis proteins, which are normally linked to blood cell membranes by the GPI anchor protein [ 2 ].
The clinical manifestations of PNH are diverse at initial presentation, and this clinical heterogenity persists through the course of the disease. However, clinical signs and symptoms that are commonly seen include anemia, dyspnea, abdominal pain, thrombosis, end-organ damage, and bone marrow failure with cytopenias [ 3 ].
In particular, thromboembolism is one of the most common causes of mortality and morbidity in PNH [ 4 ]. Other causes of death include hemorrhage, renal failure, cardiac failure, infections, myelodysplastic syndrome or aplastic anemia [ 56 ].
Even in the absence of symptoms and diagnosis, ongoing hemolysis can be destructive and the consequences may be sudden and life threatening. Historically, therapy for PNH was mainly restricted to the treatment and prevention of complications e. Eculizumab is a humanized monoclonal antibody that blocks the activation of terminal complement at C5 and prevents the formation of C5a and the terminal complement complex, C5b-9 [ 7 ].
In clinical trials, this agent has been shown to substantially reduce intravascular hemolysis and abrogate the need for blood transfusions in most patients with PNH [ 8 - 11 ]. In spite of rare spontaneous remissions, a benign course with controlled hemolysis can usually be observed in symptomatic patients during treatment with eculizumab [ 12 ]. Three cases with different presentations and courses of PNH was reported to illustrate the debilitating and sometimes fatal nature of the disease and variability of clinical presentation and outcomes.
A 58 year-old female was admitted to the emergency department due to nausea, vomiting, and abdominal pain. On physical examination she had rebound and defense, and laboratory tests revealed anemia hemoglobin, 9. Aspartate aminotransferase AST and potassium levels could not be measured due to hemolysis.
Mesenteric ischemia was observed at abdominal computed tomography CTand ileum resection and end-to-end anastomosis were performed.
Paroxysmal nocturnal hemoglobinuria
There was no documented predisposition to thrombophilia. The patient was transferred to the hematology department due to her anemia and thrombocytopenia. Her medical history revealed chronic anemia that was unresponsive to iron replacement therapy and was compatible with non-immune hemolytic anemia.
Eculizumab treatment was initiated, and hemolysis was controlled; hemoglobin elevated to No other thrombotic episodes were observed, and the patient has continued on maintenance therapy with eculizumab without any further symptoms or hemolysis.
A 61 year-old female was admitted to the emergency department due to progressive icterus, fatigue and poor performance status. Splenomegaly, abdominal pain and icterus were documented with physical examination. Laboratory tests revealed high bilirubin total bilirubin, Potassium and AST could not be measured due to hemolysis.Paroxysmal nocturnal hemoglobinuria PNH is a rare acquired, life-threatening disease of the blood.
The disease is characterized by destruction of red blood cells hemolytic anemiablood clots thrombosisand impaired bone marrow function not making enough of the three blood components. PNH affects The median age of diagnosis is years of age, with occasional cases diagnosed in childhood or adolescence. PNH is closely related to aplastic anemia. The median survival after diagnosis is 10 years; however, some patients can survive for decades with only minor symptoms.
Stem cells give rise to all the mature blood elements including red blood cellswhich carry oxygen to our tissues; white blood cellswhich fight infection; and platelets, which are involved in forming blood clots. Certain GPI-anchored proteins protect red blood cells from destruction, some are involved in blood clotting, and others are involved in fighting infection.
The majority of PNH-related issues, including destruction of red blood cells hemolytic anemiablood clots thrombosisand infection, result from a deficiency of these proteins. The genetic defect responsible for causing PNH has been identified. Knowledge of the genetic defect will allow researchers to study the disease in a manner that was not previously possible, and may give insight for developing more effective therapies.
If your doctor suspects PNH, he or she may order a variety of blood tests to confirm the diagnosis. Over the past several years, flow cytometry has become the gold standard for making the diagnosis.
This laboratory technique allows clinicians to count blood cells in a sample. PNH is characterized by hemolytic anemia, bone marrow failure and a tendency toward the development of thrombosis.
The condition has three main subtypes: classical PNH, which includes patients who have evidence of PNH in the absence of another bone marrow failure disorder; PNH in the context of other primary bone marrow disorders, such as aplastic anemia or myelodysplastic syndrome; and subclinical PNH, in which patients have small PNH clones but no clinical or laboratory evidence of hemolysis red blood cell destruction or thrombosis blood clots.
Due to the wide spectrum of symptoms associated with PNH, it is not unusual for months or years to pass before the correct diagnosis is established. Overall, the most common symptoms of PNH include:. Other issues include abdominal pain crises and back pain. Frequently patients notice their urine is the color of dark tea. Typically, hemoglobinuria will be most noticeable in the morning, and clear as the day progresses.
Attacks of hemoglobinuria may be brought on by infections, alcohol, exercise, stress or certain medications. Many patients note a feeling of fatigue that may be disabling during periods of hemoglobinuria. The excessive fatigue does not appear to be related to the degree of anemia, as it improves when the hemoglobinuria abates. Blood clots thrombosis occur almost exclusively in veins, as opposed to arteries, and are the leading cause of death in PNH.
The most common sites for blood clots are in the hepatic vein a vein that drains the liver. Clots here are also referred to as Budd-Chiari syndrome and in the sagittal vein a vein in the head. However, they can occur in any vein, especially those in the abdomen. The appropriate treatment for PNH depends on the severity of symptoms. Some patients will experience few or no symptoms from PNH and do not require treatment other than folic acid and sometimes iron supplementation to increase red blood cell production.
Over time, the disease may progress and more aggressive supportive care may be indicated depending on the patients' symptoms. Medications that increase the risk for thrombosis, such as oral birth control pills, should be avoided. PNH, like aplastic anemia, is often associated with bone marrow failure resulting in very low blood counts. The drug reduces the risk of thrombosis and can improve quality of life in PNH patients. It is the only medical therapy for PNH approved by the U. Food and Drug Administration.
It may be appropriate for patients who do not respond to eculizumab or for those who have severe reductions in red blood cells, white blood cells and platelets.Paroxysmal nocturnal hemoglobinuria PNH is a rare, acquired,  life-threatening disease of the blood characterized by destruction of red blood cells by the complement systema part of the body's innate immune system.
This destructive process occurs due to the presence of defective surface protein DAF on the red blood cellwhich normally functions to inhibit such immune reactions. Since the complement cascade attacks the red blood cells within the blood vessels of the circulatory systemthe red blood cell destruction hemolysis is considered an intravascular hemolytic anemia. Other key features of the disease, such as the high incidence of blood clot formationare incompletely understood.
PNH is the only hemolytic anemia caused by an acquired rather than inherited intrinsic defect in the cell membrane deficiency of glycophosphatidylinositol leading to the absence of protective proteins on the membrane.
Only a minority of affected people have the telltale red urine in the morning that originally gave the condition its name. Allogeneic bone marrow transplantation is the only cure, but has significant rates of additional medical problems and death.
The classic sign of PNH is red discoloration of the urine due to the presence of hemoglobin and hemosiderin from the breakdown of red blood cells. This phenomenon mainly occurs in those who have the primary form of PNH, who will notice this at some point in their disease course. The remainder mainly experience the symptoms of anemia, such as tiredness, shortness of breathand palpitations.
A small proportion of patients report attacks of abdominal paindifficulty swallowing and pain during swallowingas well as erectile dysfunction in men; this occurs mainly when the breakdown of red blood cells is rapid, and is attributable to spasm of smooth muscle due to depletion of nitric oxide by red cell breakdown products.
Forty percent of people with PNH develop thrombosis a blood clot at some point in their illness. This is the main cause of severe complications and death in PNH. These may develop in common sites deep vein thrombosis of the leg and resultant pulmonary embolism when these clots break off and enter the lungsbut in PNH blood clots may also form in more unusual sites: the hepatic vein causing Budd-Chiari syndromethe portal vein of the liver causing portal vein thrombosisthe superior or inferior mesenteric vein causing mesenteric ischemia and veins of the skin.
Cerebral venous thrombosisan uncommon form of strokeis more common in those with PNH. All cells have proteins attached to their membranes, often serving as a mode of communication or signaling between the cell and the surrounding environment. These signaling proteins are physically attached to the cell membrane in various ways, commonly anchored by glycolipids such as glycosyl phosphatidylinositols GPI.
PNH occurs as a result of a defect in the assembling of these glycolipid-protein structures on the surface of blood cells. The gene that codes for PIGA is located on the X chromosomewhich means that only one active copy of the gene for PIGA is present in each cell initially, females have two copies, but one is silenced through X-inactivation. When this mutation occurs in a hematopoietic stem cell in the bone marrow, all of the cells it produces will also have the defect.
Several of the proteins that anchor to GPI on the cell membrane are used to protect the cell from destruction by the complement systemand, without these anchors, the cells are more easily targeted by the complement proteins.
The symptoms of esophageal spasmerectile dysfunction, and abdominal pain are attributed to the fact that hemoglobin released during hemolysis binds with circulating nitric oxidea substance that is needed to relax smooth muscle. This theory is supported by the fact that these symptoms improve on administration of nitrates or sildenafil Viagrawhich improves the effect of nitric oxide on muscle cells.
Historically, the role of the sleep and night in this disease the "nocturnal" component of the name has been attributed to acidification of the blood at night due to relative hypoventilation and accumulation of carbon dioxide in the blood during sleep. This hypothesis has been questioned by researchers who note that not all those with PNH have increased hemolysis during sleep, so it is uncertain how important a role sleep actually plays in this disease.
Blood tests in PNH show changes consistent with intravascular hemolytic anemia : low hemoglobinraised lactate dehydrogenaseraised bilirubin a breakdown product of hemoglobinand decreased levels of haptoglobin ; there can be raised reticulocytes immature red cells released by the bone marrow to replace the destroyed cells if there is no iron deficiency present.
In this case, anemia may be caused by insufficient red blood cell production in addition to the hemolysis. Historically, the sucrose lysis test, in which a patient's red blood cells are placed in low-ionic-strength solution and observed for hemolysis, was used for screening.
If this was positive, the Ham's acid hemolysis test after Dr Thomas Ham, who described the test in was performed for confirmation. This is now an obsolete test for diagnosing PNH due to its low sensitivity and specificity. Today, the gold standard is flow cytometry for CD55 and CD59 on white and red blood cells.