Jean presents to her family doctor complaining of recurring abdominal pain, diarrhea and bloody stools. What is the most likely diagnosis?

A. Increased viscosity of blood: A reduction in erythrocytes decreases the overall hematocrit, which lowers blood viscosity rather than increasing it. Increased viscosity is more commonly associated with polycythemia or dehydration, not anemia.

B. Decreased cardiac output: Initially, the body compensates for anemia by increasing heart rate and stroke volume to maintain oxygen delivery, so cardiac output may initially remain normal or even increase. A decrease would occur only if compensation fails or the anemia is severe.

C. Altered coagulation: A reduction in erythrocytes primarily affects oxygen-carrying capacity rather than the coagulation system. Coagulation abnormalities are not a direct consequence of anemia unless there is an underlying hematologic disorder.

D. Hyperdynamic circulation: Following a reduction in erythrocytes, the cardiovascular system compensates by increasing heart rate and cardiac output, resulting in hyperdynamic circulation. This helps maintain tissue oxygenation despite decreased oxygen-carrying capacity of the blood.

A. Iron deficiency: Iron deficiency anemia results from inadequate iron for hemoglobin synthesis, leading to small, pale red blood cells. The bone marrow itself is usually functioning normally, but the substrate for RBC production is insufficient.

B. Pernicious: Pernicious anemia is caused by vitamin B12 deficiency, often due to intrinsic factor deficiency. While red blood cell production is affected, the underlying problem is nutritional and not a direct malfunction of the bone marrow.

C. Sickle cell: Sickle cell anemia is a genetic disorder causing abnormal hemoglobin formation, leading to sickle-shaped red blood cells. The bone marrow can produce red blood cells, but they are structurally defective and have a shortened lifespan.

D. Aplastic: Aplastic anemia occurs when the bone marrow fails to produce sufficient red blood cells, white blood cells, and platelets. This primary marrow dysfunction leads to pancytopenia and is directly related to impaired hematopoiesis.

E. Hemolytic: Hemolytic anemia results from premature destruction of red blood cells, either inherited or acquired. The bone marrow may respond by increasing RBC production, so the marrow itself is not the primary site of dysfunction.