Hemolytic anemia in children

Hemolytic anemia in children is about 5.3% among other blood diseases, and 11.5% among anemic conditions. The structure of hemolytic anemia is dominated by hereditary forms of the disease.

Hemolytic anemia is a group of diseases, the most characteristic of which is increased destruction of the blood cells caused by the reduction of their life expectancy. It is known that the normal lifespan of red blood cells is 100-120 days; about 1% of erythrocytes are daily removed from peripheral blood and replaced by an equal number of new cells from the bone marrow. Under normal conditions, this process creates dynamic equilibrium, ensuring a constant number of red blood cells in the blood. While reducing the life span of red blood cells, their destruction in the peripheral blood is more intense than the formation in the bone marrow and release into the peripheral blood. In response to a reduction in the life span of red blood cells, the activity of the bone marrow is increased 6-8 times, which is confirmed by reticulocytosis in peripheral blood. Continuing reticulocytosis in combination with varying degrees of anemia or even stable hemoglobin levels may indicate the presence of hemolysis.

[1], [2], [3], [4], [5], [6]

Epidemiology

Hemolytic anemia in children is about 5.3% among other blood diseases, and 11.5% among anemic conditions. Hereditary forms of disease predominate in the structure of hemolytic. 

What causes hemolytic anemia?

Acute hemoglobinuria

1. Incompatible blood transfusion
2. Drugs and Chemicals
   1. Permanently hemolytic anemia drugs: phenylhydrazine, sulfones, phenacetin, acetanilide (large doses) chemicals: nitrobenzene, lead toxins: snake bites and spiders
   2. Periodically causing hemolytic anemia:
      1. Associated with G-6-PD deficiency: antimalarial (primaquine); antipyretics (aspirin, phenacetin); sulfonamides; nitrofurans; vitamin K; naphthalene; favism
      2. HbZurich Associated Sulfonamides
      3. For hypersensitivity: quinine; quinidine; para-aminosalicylic acid; phenacetin
3. Infections
   1. bacterial: Clostridium perfringens; Bartonella bacilliformis
   2. parasitic: malaria
4. Burns
5. Mechanical (eg artificial valves)

[7], [8], [9], [10], [11], [12]

Chronic hemoglobinuria

1. Paroxysmal cold hemoglobinuria; syphilis ;
2. Idiopathic paroxysmal night hemoglobinuria
3. Marching hemoglobinuria
4. With hemolysis due to cold agglutinins

[13], [14], [15], [16], [17], [18], [19], [20]

Pathogenesis of hemolytic anemia

In patients with hemolytic anemia with compensatory hyperplasia of the erythroid sprout, periodically so-called aregenerative (aplastic) crises may be observed, characterized by severe deficiency. The bone marrow with predominant lesion of the erythroid sprout. In the regenerative crisis, a sharp decrease in the number of reticulocytes is observed, up to their complete disappearance from peripheral blood. Anemia can quickly turn into a heavy, life-threatening form, since even partial compensation of the process is impossible due to the shortened red blood cell lifespan. Crises are potentially dangerous, life-threatening complications in any hemolytic process.

Hemolysis called diffusion hemoglobin from erythrocytes. With the destruction of "old" red blood cells in the spleen, liver, bone marrow, hemoglobin is secreted, which is bound by plasma proteins haptoglobin, hemopexin, albumin. These complex compounds are subsequently captured by hepatocytes. Haptoglobin is synthesized in the liver, belongs to the class of alpha ₂ -globulin. During hemolysis, a complex compound hemoglobin-haptoglobin is formed, which does not penetrate the glomerular barrier of the kidneys, which provides protection against damage to the renal tubules and iron loss. Hemoglobin-haptoglobin complexes are removed from the vascular bed by cells of the reticuloendothelial system. Haptoglobin is a valuable indicator of the hemolytic process; in severe hemolysis, the consumption of haptoglobin exceeds the ability of the liver to synthesize it, and therefore its level in serum is significantly reduced.

Bilirubin is a product of heme catabolism. Under the influence of hemoxygenase contained in the macrophages of the spleen, liver, bone marrow, the a-methine bridge of the tetrapyrrole nucleus breaks in the heme, which leads to the formation of verdohemoglobin. At the next stage, the iron is split off, with the formation of biliverdin. Under the influence of cytoplasmic biliverdin reductase, biliverdin is converted to bilirubin. Free (unconjugated) bilirubin released from macrophages, when released into the bloodstream, binds to albumin, which delivers bilirubin to hepatocytes. In the liver, albumin is separated from bilirubin, then, in the hepatocyte, non-conjugated bilirubin is bound to glucuronic acid, and monoglucuronic bilirubin (MGB) is formed. MGB is excreted in bile, where it turns into diglucuronid bilirubin (DGB). DGB from bile is secreted into the intestine, where, under the influence of microflora, it is restored to colorless urobilinogen pigment, and later to pigmented stercobilin. Hemolysis dramatically increases the content of free (unconjugated, indirect) bilirubin in the blood. Hemolysis contributes to enhanced excretion of heme pigments in bile. Already in the 4th year of life, the child can form pigment stones consisting of calcium bilirubinate. In all cases of pigmentary cholelithiasis in children, it is necessary to exclude the possibility of a chronic hemolytic process.

If the amount of free hemoglobin in plasma exceeds the reserve hemoglobin-binding capacity of haptoglobin, and the supply of hemoglobin from hemolyzed erythrocytes in the vascular bed continues, hemoglobinuria occurs. The appearance of hemoglobin in the urine gives it a dark color (the color of dark beer or a strong solution of potassium permanganate). This is due to the content of both hemoglobin and methemoglobin that forms when urine is standing, as well as hemoglobin decomposition products, hemosiderin and urobilin.

Depending on the location, it is customary to distinguish intracellular and intravascular hemolysis variants. In intracellular hemolysis, erythrocyte destruction occurs in the cells of the reticuloendothelial system, primarily in the spleen, to a lesser extent in the liver and bone marrow. Clinically observed ikterichnost skin and sclera, splenomegaly, possible hepatomegaly. A significant increase in the level of indirect bilirubin is recorded, the level of haptoglobin decreases.

With intravascular hemolysis, the destruction of red blood cells occurs directly in the bloodstream. Patients have fever, chills, pains of various localization. Ikterichnost skin and sclera moderate, the presence of splenomegaly is not typical. The concentration of free hemoglobin in plasma increases dramatically (blood serum acquires brown color due to the formation of methemoglobin), the level of haptoglobin decreases significantly up to its complete absence, hemoglobinuria occurs, which can cause the development of acute renal failure (obstruction of the renal tubules by detritus ), the development of DIC is possible. Starting from the 7th day from the beginning of the hemolytic crisis in the urine, hemosiderin is detected.

[21], [22]

Pathophysiology of hemolytic anemia

The membrane of aging red blood cells is gradually destroyed, and they are cleared from the bloodstream by phagocytic cells of the spleen, liver and bone marrow. The destruction of hemoglobin occurs in these cells and hepatocytes with the help of the oxygenation system, with the preservation (and subsequent recycling) of iron, the degradation of heme to bilirubin through a series of enzymatic transformations with the reutilization of protein.

Increased unconjugated (indirect) bilirubin and jaundice manifest when the conversion of hemoglobin to bilirubin exceeds the ability of the liver to form bilirubin glucuronide and its excretion with bile. Catabolism of bilirubin is the cause of increased stercobilin in feces and urobilinogen in the urine and sometimes the formation of gallstones.

Hemolytic anemia

Mechanism

Disease

Hemolytic anemia associated with an internal red blood cell abnormality

Hereditary hemolytic anemia associated with structural or functional disorders of the erythrocyte membrane	Congenital erythropoietic porphyria. Hereditary elliptocytosis. Hereditary Spherocytosis
Acquired hemolytic anemia associated with structural or functional disorders of the erythrocyte membrane	Gyphophosphatemia. Paroxysmal night hemoglobinuria. Stomatocytosis
Hemolytic anemia associated with impaired metabolism of red blood cells	Enzyme defect of the Embden-Meyerhof path. G6FD deficiency
Anemia associated with impaired globin synthesis	Carriage of stable abnormal HB (CS-CE). Sickle cell anemia. Thalassemia

Hemolytic anemia associated with external exposure

Hyperactivity of the reticuloendothelial system	Hypersplenism
Hemolytic anemia associated with exposure to antibodies	Autoimmune hemolytic anemia: with heat antibodies; with cold antibodies; paroxysmal cold hemoglobinuria
Hemolytic anemia associated with exposure to infectious agents	Plasmodium. Bartonella spp
Hemolytic anemia associated with mechanical trauma	Anemia caused by the destruction of red blood cells in contact with the prosthetic heart valves. Anemia caused by trauma. Marching hemoglobinuria

Hemolysis mainly occurs extravascularly in phagocytic cells of the spleen, liver and bone marrow. The spleen usually helps to reduce the life span of red blood cells by destroying abnormal red blood cells, as well as red blood cells that have thermal antibodies on the surface. An enlarged spleen can sequester even normal red blood cells. Erythrocytes with pronounced anomalies, as well as cold antibodies or complement (SZ) present on the membrane surface are destroyed within the bloodstream or in the liver, from which destroyed cells can be effectively removed.

Intravascular hemolysis is rare and leads to hemoglobinuria in cases where the amount of hemoglobin released in the blood plasma exceeds the hemolobin-binding capacity of proteins (for example, haptoglobin, which is normally present in plasma at a concentration of about 1.0 g / l). Unbound hemoglobin is reabsorbed by renal tubular cells, where iron is converted to hemosiderin, one part of which is assimilated for recycling, and the other part is eliminated by urine when the tubule cells are overloaded.

Hemolysis can be acute, chronic or episodic. Chronic hemolysis may be complicated by an aplastic crisis (temporary failure of erythropoiesis), more often as a result of infection, usually caused by a parvovirus.

[23]

Symptoms of hemolytic anemia

Hemolytic anemia, regardless of the reasons that directly cause hemolysis, has in its course of 3 periods: the period of hemolytic crisis, the period of subcompensation of hemolysis and the period of compensation of hemolysis (remission). A hemolytic crisis is possible at any age and is most often triggered by an infectious disease, vaccination, chilling or medication, but it can also occur for no apparent reason. During the crisis period, hemolysis increases dramatically and the body is not able to quickly replenish the required number of red blood cells and transfer the indirect bilirubin formed in excess to a straight line. Thus, hemolytic crisis includes bilirubin intoxication and anemic syndrome.

Symptoms of hemolytic anemia, and more specifically bilirubin intoxication syndrome, are characterized by icteric skin and mucous membranes, nausea, vomiting, abdominal pain, dizziness, headaches, fever, and in some cases, disorders of consciousness, seizures. Anemic syndrome is represented by pallor of the skin and mucous membranes, expansion of the borders of the heart, deafness of tones, tachycardia, systolic murmur at the apex, shortness of breath, weakness, dizziness. With intracellular hemolysis, hepatosplenomegaly is typical, and intravascular or mixed hemolysis is characterized by a change in urine coloration due to hemoglobinuria.

During the hemolytic crisis, the following complications of hemolytic anemia are possible: acute cardiovascular insufficiency (anemic shock), DIC, regenerative crisis, acute renal failure, bile thickening syndrome. The period of subcompensation of hemolysis is also characterized by an increased activity of the erythroid sprout of the bone marrow and liver, but only to the extent that it does not lead to the compensation of the main syndromes. In this regard, the patient may have moderate clinical symptoms: pallor, skin and mucous membranes, slight (or pronounced, depending on the form of the disease) enlargement of the liver and / or spleen. Variations in the number of erythrocytes from the lower limit of normal to 3.5-3.2 x 10 ¹² / l and, respectively, hemoglobin in the range of 120-90 g / l, as well as indirect hyperbilirubinemia up to 25-40 µmol / l are possible. In the hemolysis compensation period, the intensity of erythrocyte destruction is significantly reduced, the anemic syndrome is completely stopped due to the hyperproduction of erythrocytes in the erythroid sprout of the bone marrow, while the content of reticulocytes is always increased. At the same time, the active work of the liver in converting indirect bilirubin to a straight line ensures a reduction in the level of bilirubin to normal.

Thus, both of the main pathogenetic mechanisms responsible for the severity of the patient’s condition during a hemolytic crisis are arrested in the compensation period due to increased bone marrow and liver function. The child at this time there are no clinical manifestations of hemolytic anemia. Complications in the form of hemosiderosis of internal organs, biliary dyskinesia, spleen pathology (heart attacks, subcapsular ruptures, hypersplenism syndrome) are also possible in the period of hemolysis compensation.

[24]

Structure of hemolytic anemia

Currently, it is generally accepted to isolate hereditary and acquired forms of hemolytic anemia.

Among the hereditary hemolytic anemia, depending on the nature of the erythrocyte lesion, forms associated with impaired erythrocyte membranes (disturbed membrane protein structure or membrane lipid abnormalities) are isolated; forms associated with impaired activity of erythrocyte enzymes (pentose phosphate cycle, glycolysis, glutathione exchange, and others) and forms associated with impaired structure or hemoglobin synthesis. In hereditary hemolytic anemias, a reduction in the life span of red blood cells and premature hemolysis are genetically determined: 16 syndromes with a dominant type of inheritance, 29 with recessive and 7 phenotypes inherited, linked to the X chromosome are distinguished. Hereditary forms prevail in the structure of hemolytic anemia.

[25], [26], [27]

Acquired hemolytic anemia

With acquired hemolytic anemias, the erythrocyte's life expectancy decreases under the influence of various factors; therefore, they are classified according to the principle of clarifying the factors causing hemolysis. These are anemias associated with exposure to antibodies (immune), with mechanical or chemical damage to the erythrocyte membrane, destruction of erythrocytes by the parasite ( malaria ), lack of vitamins (vitamin E deficiency), changes in the structure of membranes caused by somatic mutation ( paroxysmal night hemoglobinuria ).

In addition to the above signs, common to all hemolytic anemias, there are symptoms pathognomonic for a particular form of the disease. Each hereditary form of hemolytic anemia has its own differential diagnostic characters. Differential diagnosis between various forms of hemolytic anemia should be carried out in children over the age of one year, since at this time the anatomical and physiological features of the blood of young children disappear: physiological macrocytosis, fluctuations in the number of reticulocytes, the prevalence of fetal hemoglobin, the relatively low limit of minimal osmotic resistance red blood cells.

[28], [29], [30]

Hereditary hemolytic anemia

Hereditary hemolytic anemia associated with disturbance of the erythrocyte membrane (membranopathy)

Membranopathies are characterized by a hereditarily caused defect in the structure of the protein of the membrane or in violation of the lipids of the erythrocyte membrane. Autosomal dominant or augosomno-recessive are inherited.

Hemolysis is localized, as a rule, intracellularly, that is, the destruction of red blood cells occurs mainly in the spleen, to a lesser extent - in the liver.

Classification of hemolytic anemia associated with disturbance of the erythrocyte membrane:

1. Violation of the erythrocyte membrane protein structure
   1. hereditary microspherocytosis ;
   2. hereditary elliptocytosis;
   3. hereditary stomatocytosis;
   4. hereditary pyropoikilocytosis.
2. Erythrocyte membrane lipid damage
   1. hereditary acanthocytosis;
   2. hereditary hemolytic anemia due to a lack of lecithin-cholesterol acyl transferase activity;
   3. hereditary non-spherocytic hemolytic anemia due to an increase in the membrane of erythrocytes phosphatidylcholine (lecithin);
   4. children's infantile pyknocytosis.

Violation of the erythrocyte membrane protein structure

Rare forms of hereditary anemia caused by disturbance of the structure of proteins of the erythrocyte membrane

Hemolysis in these forms of anemia occurs intracellularly. Hemolytic anemia has varying degrees of severity - from mild to severe, requiring blood transfusions. Pallor of skin and mucous membranes, jaundice, splenomegaly, development of gallstone disease is possible.

[31], [32]

Structure of hemolytic anemia

At present, it is generally accepted to separate inherited and acquired forms of hemolytic anemia.

Among hereditary hemolytic anemias, depending on the nature of erythrocytes lesion, several forms are distinguished: forms, associated with erythrocytes membrane violation (violation of the structure of the membrane protein or lipid membrane violation); forms, associated with disrupted enzyme activity of erythrocytes (pentose phosphate cycle, glycolysis, glutathione metabolism and others) and forms, associated with disruption of the structure and synthesis of hemoglobulin. During hereditary hemolytic anemias, reduced life expectancy and premature erythrocyte hemolysis are genetically determined: 16 syndromes with dominant inheritance, 29 - with recessive and 7 phenotypes, inherited, linked to the X chromosome are distinguished. Hereditary forms predominate in the structure of hemolytic anemia.

Acquired hemolytic anemia

During acquired hemolytic anemia, lifespan of red blood cells is reduced under the influence of various factors, so they are classified on the basis of clarifying factors, causing hemolysis. These anemias are associated with exposure to antibodies (immune), to mechanical or chemical damage of red blood cells membranes, red blood cell destruction by parasite (malaria), vitamin deficiency (deficiency of vitamin E), with changes in membrane structure, caused by somatic mutation (paroxysmal nocturnal hemoglobinuria).

In addition to the above features, common to all hemolytic anemias, there are symptoms, pathognomonic for a particular form of the disease. Each hemolytic anemia hereditary form has its differential diagnostic signs. Differential diagnosis between different forms of hemolytic anemia should be performed in children older than one year, since, at this time, anatomical and physiological features, characteristic to the blood of young children: physiological macrocytosis, fluctuations in the number of reticulocytes, prevalence of fetal hemoglobin, relatively low limit of the minimum osmotic resistance of erythrocytes, disappear.

Hereditary hemolytic anemia

Hereditary hemolytic anemia related to violation of erythrocyte membranes (membranopathy)

Membranopathy is characterized by genetically caused defect of structure of protein membrane or violation of erythrocyte membrane lipids. They are inherited by autosomal dominant or autosomal recessive way.

Hemolysis is usually localized intracellular, that is, destruction of red blood cells occurs mainly in the spleen, to a lesser extent - in the liver.

Classification of hemolytic anemia associated with disrupted erythrocyte`s membranes:

Violation of structure of erythrocyte membrane protein

• hereditary microspherocytosis;
• hereditary ovalocytosis;
• hereditary stomatocytosis;
• hereditary pyropoikilocytosis.

Violation of erythrocyte membrane lipids

• hereditary acanthocytosis;
• hereditary hemolytic anemia, caused by deficiency of lecithin – cholesterol- acyl -transferase activity;
• hereditary nonspherocytic hemolytic anemia due to increase in  erythrocyte membrane of phosphatidylcholine (lecithin);
• children`s infantile pinocytosis.

Violation of structure of erythrocyte membrane proteins

Rare forms of hereditary anemia, caused by disruption of structure of erythrocyte membrane proteins

Hemolysis under these forms of anemia occurs intracellularly. Hemolytic anemia has varying degrees of severity - from mild to severe, requiring blood transfusions. Pallor of skin and mucous, jaundice, splenomegaly are observed, also cholelithiasis may develop.

Diagnosis of hemolytic anemia

Hemolysis is assumed in patients with anemia and reticulocytosis, especially in the presence of splenomegaly, as well as other possible causes of hemolysis. If hemolysis is suspected, a peripheral blood smear is examined, serum bilirubin, LDH, and ALT are determined. If these studies fail, hemosiderin, urine hemoglobin, and serum haptoglobin are determined.

Hemolysis suggests the presence of morphological changes in red blood cells. The most typical of active hemolysis is erythrocyte spherocytosis. Fragments of erythrocytes (schistocytes) or erythrophagocytosis in blood smears suggests intravascular hemolysis. When spherocytosis there is an increase in the ICSU index. The presence of hemolysis can be suspected with increased levels of serum LDH and indirect bilirubin with normal ALT and the presence of urinary urobilinogen. Intravascular hemolysis is expected when a low serum haptoglobin level is detected, however, this indicator may be reduced in liver dysfunction and increased in the presence of systemic inflammation. Intravascular hemolysis is also suspected when hemosiderin or hemoglobin is detected in the urine. The presence of hemoglobin in the urine, as well as hematuria and myoglobinuria, is determined by a positive benzidine test. Differential diagnosis of hemolysis and hematuria is possible on the basis of the absence of red blood cells in urine microscopy. Free hemoglobin, unlike myoglobin, can stain the plasma brown, which manifests itself after centrifuging the blood.

Morphological changes of erythrocytes with hemolytic anemia

Morphology	The reasons
Spherocytes	Transfused erythrocytes, hemolytic anemia with thermal antibodies, hereditary spherocytosis
Systocytes	Microangiopathy, intravascular prosthetics
Target	Hemoglobinopathies (Hb S, C, thalassemia), liver pathology
Sore-like	Sickle cell anemia
Agglutinated cells	Cold agglutinins disease
Heinz Taurus	Activation of peroxidation, unstable Нb (for example, G6PD deficiency)
Nucleated red blood cells and basophilia	Great beta thalassemia
Acanthocytes	Anemia with spore erythrocytes

Although the presence of hemolysis can be ascertained using these simple tests, the decisive criterion is the determination of the lifetime of the red blood cells by examining with a radioactive label, such as ⁵¹ Cr. Determining the lifetime of labeled red blood cells can reveal the presence of hemolysis and the place of their destruction. However, this study is rarely used.

If hemolysis is detected, it is necessary to establish the disease that provoked it. One of the ways to limit the differential search for hemolytic anemia is to analyze the patient’s risk factors (for example, geographical location of the country, heredity, existing diseases), identify splenomegaly, determine the direct antiglobulin test (Coombs), and study the blood smear. Most hemolytic anemias have abnormalities in one of these options, which may direct further searching. Other laboratory tests that can help determine the cause of hemolysis are quantitative electrophoresis of hemoglobin, erythrocyte enzymes, flow cytometry, determination of cold agglutinins, osmotic resistance of erythrocytes, acid hemolysis, glucose test.

Although certain tests may help in the differential diagnosis of intravascular from extravascular hemolysis, it is difficult to establish these differences. During the intensive destruction of red blood cells, both of these mechanisms take place, although to varying degrees.

[33], [34], [35],

Hemolytic anemia treatment

Treatment of hemolytic anemia depends on the specific hemolysis mechanism. Hemoglobinuria and hemosiderinuria may require iron replacement therapy. Prolonged transfusion therapy leads to intensive iron deposition, which requires chelate therapy. Splenectomy can be effective in some cases, especially when sequestration in the spleen is the main cause of red blood cell destruction. After the use of pneumococcal and meningococcal vaccines, as well as Haemophilus influenzae vaccines, splenectomy is delayed for as long as possible for 2 weeks.

[36], [37]