Evolutionary dynamics of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by hemolysis and a high risk of thrombosis, that is due to a deficiency in several cell surface proteins that prevent complement activation. Its origin has been traced to a somatic mutation in the PIG-A gene within hematopoietic stem cells (HSC). However, to date the question of how this mutant clone expands in size to contribute significantly to hematopoiesis remains under debate. One hypothesis posits the existence of a selective advantage of PIG-A mutated cells due to an immune mediated attack on normal HSC, but the evidence supporting this hypothesis is inconclusive. An alternative (and simpler) explanation attributes clonal expansion to neutral drift, in which case selection neither favours nor inhibits expansion of PIG-A mutated HSC. Here we examine the implications of the neutral drift model by numerically evolving a Markov chain for the probabilities of all possible outcomes, and investigate the possible occurrence and evolution, within this framework, of multiple independently arising clones within the HSC pool. Predictions of the model agree well with the known incidence of the disease and average age at diagnosis. Notwithstanding the slight difference in clonal expansion rates between our results and those reported in the literature, our model results lead to a relative stability of clone size when averaging multiple cases, in accord with what has been observed in human trials. The probability of a patient harbouring a second clone in the HSC pool was found to be extremely low ([Formula: see text]). Thus our results suggest that in clinical cases of PNH where two independent clones of mutant cells are observed, only one of those is likely to have originated in the HSC pool.

Early-onset chronic axonal neuropathy, strokes, and hemolysis: inherited CD59 deficiency.

OBJECTIVE: To identify the underlying etiology of 3 patients in a multiplex family with strokes, chronic immune-mediated peripheral neuropathy, and hemolysis. All had onset in infancy. METHODS: We performed genome-wide linkage analysis followed by whole exome sequencing (WES) in the proband, Sanger sequencing, and segregation analysis of putative mutations. In addition, we conducted flow cytometry studies to assess CD59 expression. RESULTS: In a 2-generation-3-affected family with early-onset immune-mediated axonal neuropathy, cerebrovascular event both in the anterior and posterior circulation, and chronic Coombs-negative hemolysis, we detected CD59 deleterious mutation as the underlying cause. Linkage analysis and homozygosity mapping using single nucleotide polymorphism (SNP) microarrays in the family followed by WES in one index case allowed identification of a homozygous missense mutation in the CD59 gene (c.A146T:p.Asp49Val). Sanger sequencing validated the mutation, showing cosegregation with the disease phenotype. Flow cytometry using blood cells in the 3 patients showed a lack of CD59 expression at the cell membrane compared to control and CD55 labeling. CONCLUSION: We added to the knowledge base about inherited CD59 deficiency.

Hemoglobinuric acute kidney injury from aortic root graft malfunction.

Hemolysis and consequent hemoglobinuria is a well-known cause of acute kidney injury (AKI). Hemolysis has been associated with malpositioned prosthetic valves, but other prosthetic devices may rarely be associated with red cell shear stress. We report a case of a 56-year-old man who presented with hemolysis, AKI, and anemia. During workup, he was found to have anti-phospholipid antibodies, leading to a presumptive diagnosis of catastrophic anti-phospholipid antibody syndrome. However, further investigation revealed the cause of hemolysis to be from aortic root graft dysfunction. Following replacement of the prosthesis, there was complete resolution of his hemolysis and recovery of renal function. This case underscores the need to consider cardiac prosthetic devices in patients presenting with hemoglobinuric AKI.

[Tropical malaria in children in the Republic of Tajikistan].

The complications of tropical malaria were noted in 25 (9.4%) of 196 pediatric patients followed up. These included cerebral malaria in 8 (3%), severe hemolytic anemia in 15 (5.7%), hemoglobinuric fever in 1 (0.37%), and malarial hepatitis in 1 (0.37%). The occurrence of complications was associated with the late referral of patients to a health care facility and untimely treatment, as well as with preliminary misdiagnoses (acute respiratory viral infection, typhoid-parathyphoid fever, meningitis, acute enteric infection, viral hepatitis, sepsis). The main reasons for late diagnosis were the absence of malarial paroxysm at the onset of disease in infants and the wrong type of a temperature curve.

[Pathophysiological consequences of hemolysis. Role of cell-free hemoglobin]. / Patofizjologiczne konsekwencje hemolizy. Rola wolnej hemoglobiny.

Abundant hemolysis is associated with a number of inherent and acquired diseases including sickle-cell disease (SCD), polycythemia, paroxysmal nocturnal hemoglobinuria (PNH) and drug-induced hemolytic anemia. Despite different etiopathology of hemolytic diseases, many concomitant symptoms are comparable and include e.g. hypertension, hemoglobinuria and hypercoagulation state. Studies in the last years have shown a growing list of mechanisms lying at the basis of those symptoms, in particular irreversible reaction between cell-free hemoglobin (Hb) and nitric oxide (NO) - endogenous vasorelaxant and anti-thrombotic agent. Saturation of protective physiological cell-free Hb-scavenging mechanisms results in accumulation of Hb in plasma and hemoglobinemia. Extensive hemoglobinemia subsequently leads to hemoglobinuria, which may cause kidney damage and development of Fanconi syndrome. A severe problem in patients with SCD and PNH is pulmonary and systemic hypertension. It may lead to circulation failure, including stroke, and it is related to abolition of NO bioavailability for vascular smooth muscle cells. Thrombotic events are the major cause of death in SCD and PNH. It ensues from lack of platelet inhibition evoked by Hb-mediated NO scavenging. A serious complication that affects patients with excessive hemolysis is erectile dysfunction. Also direct cytotoxic, prooxidant and proinflammatory effects of cell-free hemoglobin and heme compose the clinical picture of hemolytic diseases. The pathophysiological role of plasma Hb, mechanisms of its elimination, and direct and indirect (via NO scavenging) deleterious effects of cell-free Hb are presented in detail in this review. Understanding the critical role of hemolysis and cell-free Hb is important in the perspective of treating patients with hemolytic diseases and to design new effective therapies in future.

Cell-derived microparticles in haemostasis and vascular medicine.

Considerable interest for cell-derived microparticles has emerged, pointing out their essential role in haemostatic response and their potential as disease markers, but also their implication in a wide range of physiological and pathological processes. They derive from different cell types including platelets - the main source of microparticles - but also from red blood cells, leukocytes and endothelial cells, and they circulate in blood. Despite difficulties encountered in analyzing them and disparities of results obtained with a wide range of methods, microparticle generation processes are now better understood. However, a generally admitted definition of microparticles is currently lacking. For all these reasons we decided to review the literature regarding microparticles in their widest definition, including ectosomes and exosomes, and to focus mainly on their role in haemostasis and vascular medicine.

Cardiopulmonary bypass-associated acute kidney injury: a pigment nephropathy?

Acute kidney injury (AKI) is a common and serious postoperative complication following exposure to cardiopulmonary bypass (CPB). Several mechanisms have been proposed by which the kidney can be damaged and interventional studies addressing known targets of renal injury have been undertaken in an attempt to prevent or attenuate CPB-associated AKI. However, no definitive strategy appears to protect a broad heterogeneous population of cardiac surgery patients from CPB-associated AKI. Although the association between hemoglobinuria and the development of AKI was recognized many years ago, this idea has not been sufficiently acknowledged in past and current clinical research in the context of cardiac surgery-related AKI. Hemoglobin-induced renal injury may be a major contributor to CPB-associated AKI. Accordingly, we now describe in detail the mechanisms by which hemoglobinuria may induce renal injury and raise the question as to whether CPB-associated AKI may actually be, in a significant part, a form of pigment nephropathy where hemoglobin is the pigment responsible for renal injury. If CPB-associated AKI is a pigment nephropathy, alkalinization of urine with sodium bicarbonate might protect from: (1) tubular cast formation from met-hemoglobin; (2) proximal tubular cell necrosis by reduced endocytotic hemoglobin uptake, and (3) free iron-mediated radical oxygen species production and related injury. Sodium bicarbonate is safe, simple to administer and inexpensive. If part of AKI after CPB is truly secondary to hemoglobin-induced pigment nephropathy, prophylactic sodium bicarbonate infusion might help attenuate it. A trial of such treatment might be a reasonable future investigation in higher risk patients receiving CPB.

An innovative simple technique of blood conservation in adult patients with tetralogy of Fallot and severely raised hemoglobin.

The adult patients of tetralogy of Fallot often present with high hemoglobin levels. High hemoglobin and hematocrit on cardiopulmonary bypass (CPB) are associated with increased hemolysis, plasma free hemoglobin, renal dysfunction or failure, postoperative bleeding, exploration for bleeding, and increased requirement of allogeneic blood and blood products. Despite the presence of high hemoglobin and its association with adverse outcome, blood conservation is rarely practiced in these patients because of the fear of possible hemodynamic instability, and hypoxemic spell. We describe an innovative, simple technique of blood conservation for adult patients of tetralogy of Fallot with severely raised hemoglobin. With this technique, hemoglobin can be normalized on CPB; moreover, there is no fear of hypoxemic spell or hemodynamic instability. Furthermore, the blood conserved is readily available for transfusion in the perioperative period, if needed.

Hematopoietic stem cells in aplastic anemia.

Profound cytopenia involving all blood lineages, a hallmark of aplastic anemia (AA), can result in devastating morbidity and high mortality. Although various etiologies and distinct pathophysiologic mechanisms may be involved, a profound defect in the stem cell compartment is a unifying feature in most patients with AA. As a stem cell disease, AA is very instructive and provides insights into the function and quantity of normal hematopoietic stem cells and their ability to regenerate. Pathophysiologically, understanding of AA may reveal mechanisms as to the evolution of other related bone marrow failure syndromes such as paroxysmal nocturnal hemoglobinuria and myelodysplasia-clonal diseases of hematopoiesis associated with defective stem cells. Conversely, constitutional forms of AA occurring in association with Fanconi anemia and dyskeratosis congenita demonstrate the role of specific genes and pathways in the dysfunction of the stem cells leading to the failure of the stem cell compartment. The acquired mechanisms resulting in depletion of stem cells in AA may involve fundamental pathways such as apoptosis and senescence as well as exhaustion of proliferative capacity or excessive differentiation. Inherent in the paucity of the bone marrow in AA, the study of the stem cells in AA has been very difficult due to their natural rarity and disease-specific contraction of the stem cell pool. Despite these scientific challenges, laboratory studies and systematic clinical observation provide valuable information of significance beyond its specific application to AA.

Exertional (march) haemoglobinuria.

The case history is presented of two patients with attacks of cherry-red urine after strenuous exercise. Both had varicosity of the long saphenous veins. Haemoglobinuria disappeared after crossectomy of the long saphenous vein and resection of the convolutes. After one and two years, they have no recurrence.

Regulation of renal function in thermal injury.

Hypovolemia, low cardiac output, and systemic vasoconstriction are major etiologic factors in acute renal failure occurring in the early postburn period, and elevated levels of stress-related hormones (catecholamines, angiotensin, aldosterone, and vasopressin) are implicated in the mechanism. By counteracting the effects of the hormones, atrial natriuretic polypeptide (ANP) regulates the renal response to burns. ANP was elevated after burns, protecting the kidneys by increasing renal blood flow and urine output. In pulmonary acid injury, increased ANP levels were associated with natriuresis which was reduced by administration of anti-ANP serum. Exogenous ANP given to dogs under constant norepinephrine infusion resulted in improvement of hemodynamic and renal parameters. To prevent tubular damage due to hemoglobinuria, a haptoglobin preparation is administered to patients with extensive third-degree burns. With sufficient fluid replacement, these new treatments will reduce the incidence of acute renal failure in the early postburn period.

Development of artificial model of caval syndrome in canine heartworm disease.

In order to develop an artificial model of caval syndrome (dirofilarial hemoglobinuria), heartworm-like silicone tubes were inserted into the tricuspid valve orifice and right atrium of dogs. Fifteen to 25 tubes with some knots were inserted through the posterior vena cava in 6 dogs (knot-tube group), 7 to 12 tubes without knot (small-number group) through the jugular vein in another 5 dogs, or 25 to 35 tubes (large-number group) in yet another 5 dogs. The tubes remained in the right atrium, and a part of them protruded into the tricuspid valve orifice. The number of tubes at the tricuspid valve orifice was the greatest in the large-number group. After tube insertion, the signs of so-called "caval syndrome", such as systolic cardiac murmur, jugular pulse, anemia, and so on, were observed in almost all cases of the 3 groups, the signs were severest in the large-number group. Urine hemoglobin was detected in almost all cases of the knot-tube and large-number groups, and in 1 case in the small-number group. Ascites was observed in 1 case of the knot-tube group at 6 weeks, in 1 case of the small-number group at 7 days and in 3 cases of the large-number group at 7 days after insertion.