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Hematological system
Iron deficiency anemia
Beta-thalassemia
Alpha-thalassemia
Sideroblastic anemia
Anemia of chronic disease
Lead poisoning
Hemolytic disease of the newborn
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Autoimmune hemolytic anemia
Pyruvate kinase deficiency
Paroxysmal nocturnal hemoglobinuria
Sickle cell disease (NORD)
Hereditary spherocytosis
Anemia of chronic disease
Aplastic anemia
Fanconi anemia
Megaloblastic anemia
Folate (Vitamin B9) deficiency
Vitamin B12 deficiency
Fanconi anemia
Diamond-Blackfan anemia
Acute intermittent porphyria
Porphyria cutanea tarda
Lead poisoning
Hemophilia
Vitamin K deficiency
Bernard-Soulier syndrome
Glanzmann's thrombasthenia
Hemolytic-uremic syndrome
Immune thrombocytopenic purpura
Thrombotic thrombocytopenic purpura
Von Willebrand disease
Disseminated intravascular coagulation
Heparin-induced thrombocytopenia
Antithrombin III deficiency
Factor V Leiden
Protein C deficiency
Protein S deficiency
Antiphospholipid syndrome
Hodgkin lymphoma
Non-Hodgkin lymphoma
Chronic leukemia
Acute leukemia
Leukemoid reaction
Myelodysplastic syndromes
Polycythemia vera (NORD)
Myelofibrosis (NORD)
Essential thrombocythemia (NORD)
Langerhans cell histiocytosis
Mastocytosis (NORD)
Multiple myeloma
Monoclonal gammopathy of undetermined significance
Waldenstrom macroglobulinemia
Microcytic anemia: Pathology review
Non-hemolytic normocytic anemia: Pathology review
Intrinsic hemolytic normocytic anemia: Pathology review
Extrinsic hemolytic normocytic anemia: Pathology review
Macrocytic anemia: Pathology review
Heme synthesis disorders: Pathology review
Coagulation disorders: Pathology review
Platelet disorders: Pathology review
Mixed platelet and coagulation disorders: Pathology review
Thrombosis syndromes (hypercoagulability): Pathology review
Lymphomas: Pathology review
Leukemias: Pathology review
Plasma cell disorders: Pathology review
Myeloproliferative disorders: Pathology review
Iron deficiency anemia
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iron deficiency anemia p. 426
in anemia taxonomy p. 425
colorectal cancer p. 397
fibroid tumors p. 665
Plummer-Vinson syndrome p. 386
Jung Hee Lee, MScBMC
Jahnavi Narayanan, MBBS
Anemia is a condition where there’s a decrease in the number of healthy red blood cells, or RBCs, in the body.
So, iron deficiency anemia means anemia caused by a deficiency in iron.
Iron deficiency anemia is also the most common type of anemia worldwide.
If we take a close look at our red blood cells, we’ll notice that they’re loaded with millions of copies of the same exact protein called hemoglobin, which binds to oxygen and turns our blood cells into little oxygen transporters, and basically allow us to move oxygen to all the tissues in our body.
If we take an even closer look at those hemoglobin proteins, we’ll find that they’re made of four heme molecules, which have, right in the middle, iron.
This iron molecule is what binds to oxygen, so each hemoglobin molecule can bind four molecules of oxygen.
In addition, iron is also an important part of proteins like myoglobin, which delivers and stores oxygen in muscles; and mitochondrial enzymes like cytochrome oxidase, which help generate ATP.
Normally, when a red blood cell dies, some iron is recycled from it.
But, we also lose about 1 milligram of iron every day - some through the sweat, some in shedded skin cells, and some in shedded cells in the gastrointestinal tract, which get out of the body through feces.
But most of us take in 10-20 mg of dietary iron every day, and absorb about 10% of it, or about 1 or 2 milligrams - so it all evens out at the end of the day!
Now, our diet contains two forms of iron.
The first is heme iron, or iron bound to hemoglobin or myoglobin, which comes from animal products like meat.
Heme iron is in the ferrous, or Fe2+, state.
The other form is non-heme iron, which is free iron molecules in the ferric, or Fe3+, state.
Non-heme iron comes from plant based foods like spinach and beans.
Now, when food is broken down in the stomach, iron is released.
Heme iron is absorbed directly into the duodenal cells, where it is broken down to release Fe2+ molecules.
Non-heme iron, however, needs to be reduced to heme iron first.
So the stomach’s hydrochloric acid activates a group of enzymes in the duodenal cells, collectively called ferri-reductase, which live up to their name by reducing non-heme iron to Fe2+ molecules.
Fe2+ molecules then bind to a protein in the duodenal cells called ferritin, which temporarily stores the iron.
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