Overview
Infections hemolytic anemia is caused by the destruction of red blood cells in the course of infection by many microorganisms, shortening their lifespan and leading to hemolytic anemia. Infections can destroy red blood cells through different mechanisms, but one of them is direct destruction of red blood cells by microorganisms that cause hemolysis, and it can also lead to hemolytic anemia through immune mechanisms.
Etiology
Pathogenic microorganisms that can cause hemolytic anemia include protozoa, Pseudomonas aeruginosa, Streptococcus pneumoniae, Escherichia coli, Staphylococcus, Streptococcus, Enterobacteriaceae spp. (Salmonella spp.), Vibrio cholerae, Mycobacterium tuberculosis, Helicobacter spp. and Mycoplasma pneumoniae. Viral infections are cytomegalovirus, hepatitis virus, herpes simplex virus, mumps virus, influenza virus, varicella-zoster virus, rubella virus, and EBV.
Symptoms
1. Warm antibody type autoimmune hemolytic anemia
(1) Acute type is most common in infants and young children, and secondary type is more common. There is often a history of acute infection 1 to 2 weeks before the onset of the disease. Common symptoms include fever, pallor, malaise, loss of appetite, vomiting, abdominal pain, jaundice, darkening of the urine color to tea, soy sauce urine or wash water urine (hemoglobinuria), liver and spleen enlargement. The duration of the disease usually does not exceed 3 months.
(2) The chronic type is mostly found in older people. The main symptoms are anemia, jaundice, hepatosplenomegaly, and often hemoglobinuria. These symptoms recur during the course of the disease and are prolonged. A small number of patients with thrombocytopenia are called Evans syndrome.
2. Autoimmune hemolytic anemia of cold antibody type
(1) The symptoms are mild, and the main manifestation is cyanosis of the hands and feet due to the condensation of red blood cells in the exposed limbs during the cold weather in winter, i.e. Raynaud’s symptom.
(2) Acute type is mostly seen in infectious mononucleosis and mycoplasma pneumonia, which is transient and has a good prognosis.
(3) Chronic type of the course of the disease with the seasonal changes in the long-term persistence of repeated, and can be accompanied by systemic lupus erythematosus (SLE), chronic lymphadenitis.
3. Paroxysmal cold hemoglobinuria (PCH for short)
(1) Most of them are secondary and have a rapid onset.
(2) Acute intravascular hemolysis occurs after the patient enters a warm room from a cold outdoor area, manifested by high fever, chills, back and leg pain, abdominal pain, nausea, vomiting, diarrhea, hemoglobinuria, jaundice, and liver and spleen enlargement.
Examination
1. Blood picture
(1) The degree of anemia varies, and the mean cell volume (MCV) of red blood cells is mostly normal or increased.
(2) Reticulocyte counts are often elevated.
(3) The peripheral blood smear has an increase in spherical red blood cells, and mildly increased red blood cell size, heterogeneity, fragmentation, polyphilic and basophilic punctate red blood cells, and a few nucleated red blood cells and Howell-Jolly vesicles can also be seen.
(4) The white blood cell count varies in height depending on the concomitant disease.
(5) Platelet counts are mostly normal, but there is a marked decrease in platelets in Evans syndrome.
2. Bone marrow
(1) Most patients have significant proliferation of the erythroid lineage, but the erythroid lineage of the bone marrow may be nonproliferative or even hypoplastic in secondary cases such as infections, SLE, and malignant diseases.
(2) Sometimes, megaloblastic changes may occur.
3. Immunologic examination
Including anti-human globulin test (Coombs test), which is the most important test for diagnosis of warm antibody type AIHA; cold agglutinin test is the best method for diagnosis of cold agglutinin syndrome; cold and hot hemolysis test (D-L test) is the most reliable test to confirm the diagnosis of PCH.
4.Other
(1) Increased serum bilirubin, decreased or disappeared plasma-bound pearl protein, increased plasma free hemoglobin.
(2) The presence of hemoglobin or (and) ferritin-containing particles in the urine, and an increase in urobilinogen.
Diagnosis
1. Diagnostic criteria for warm antibody type
(1) If there is no history of blood transfusion or administration of special drugs in the past 4 months, and if the direct Coombs test is positive, combined with the clinical manifestations and laboratory tests, autoimmune hemolytic anemia of the warm antibody type can be diagnosed.
(2) If the anti-human globulin test is negative, but the clinical manifestations are more consistent, glucocorticoid or splenectomy is effective, and other hemolytic anemias (especially hereditary spherocytosis) are excluded, the diagnosis of autoimmune hemolytic anemia with negative Coombs’ test can be made.
2. Diagnostic criteria of cold antibody type
Clinical manifestations combined with laboratory examination, cold agglutinin test is positive, the potency can be as high as 1:1000 or even 1:16000 at 4℃, and the agglutinin potency is still very high in albumin or saline at 30℃, which has diagnostic significance.
3.Diagnostic criteria of PCH
Clinical manifestations combined with laboratory examination, cold and hot hemolysis test (Donath-Landsteiner) is positive; Coombs test is positive, for C3 type.
Treatment
1. Treatment of etiology
Actively search for the cause of the disease, treat the primary disease, correct the anemia and eliminate the antibody.
2. Adrenocorticotropic hormone
Prednisone 1～1.5mg/kg.d is commonly used in the treatment of warm antibody type, which is taken orally in divided doses. Symptoms improve, about 1 week after the red blood cells rise rapidly. If the treatment is ineffective for 3 weeks, it is necessary to change other therapies in time, and then reduce the dose gradually and slowly after the hemolysis stops and the number of red blood cells returns to normal.
3. Splenectomy
The effective rate of warm-antibody type is 50%～70%, but it is generally ineffective for cold-antibody type.
4. Immunosuppressants
Commonly used drugs are azathioprine, cyclophosphamide, aminoglutethimide and cyclosporine A, etc.
5. Others
Blood transfusion needs to be careful, mainly for hemolytic crisis or extreme anemia, if necessary, transfusion of washed red blood cells. High-dose gammaglobulin (IVIG) or plasma exchange therapy can be tried.