Anemias (IV) - Hemolytic Anemias

You’ve surely heard of someone who can’t eat fava beans.
After eating them, they experience chills, fever, back and abdominal pain, their blood pressure drops significantly, and then they develop jaundice (their skin turns yellow) and their urine becomes very dark. This acute condition is aptly named favism (from fava beans) and belongs to the group of hemolytic anemias (HA). These conditions have very different origins and causes.
The acute form is not the most common. It often manifests only with the classic symptoms of anemia (chronic fatigue, weakness, shortness of breath, headaches, etc.) and mild jaundice (yellowing) of the sclera (the white of the eye). At its root is the premature and abnormal destruction of red blood cells (RBCs). This destruction has causes that are both intrinsic and extrinsic to the RBCs. Among the extrinsic causes, the following stand out:

1. Mechanical obstructions in blood circulation. In diseases that cause splenomegaly (enlarged spleen)—such as malaria—the enlarged spleen traps and fragments red blood cells. Artificial heart valves or aneurysms also fragment red blood cells. A large number of these red blood cells, elevated bilirubin (a yellow substance derived from hemoglobin), and laboratory signs of anemia lead to a diagnosis of microangiopathic hemolytic anemia (microangio = small blood vessel). The treatment is almost always surgical.

2. The body’s immune system attacks and destroys red blood cells because it no longer recognizes them as its own. This is autoimmune hemolytic anemia. The presence of autoantibodies that bind to red blood cells facilitates their destruction by the spleen. There are forms of hemolytic anemia caused by warm antibodies (which are active at body temperature) and forms caused by cold antibodies or “ab frigore.”
The laboratory will perform a Coombs test; if positive, it confirms the immunological origin of the anemia. “Ab frigore” autoimmune hemolytic anemias arise during acute infections, in leukemias and lymphomas, and upon exposure to cold. The others occur in lupus, but in 50% of cases, the cause is unknown. In one-third of cases, corticosteroids are the treatment of choice, with splenectomy reserved for cases in which they fail. Another form of immune-mediated anemia is the rare paroxysmal nocturnal hemoglobinuria, in which the sudden (paroxysmal) destruction of large quantities of red blood cells causes severe hemoglobinuria (blood in the urine) and the formation of clots in the large veins of the abdomen and legs.

3. Infection by parasites in the circulating blood (malaria) or by various bacteria (septicemia). As for favism, I will explain it in the next article, in which I will discuss the intrinsic causes of red blood cells that account for hemolytic anemia.