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Autoimmune hemolytic anemia
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hemolytic disease of the newborn
Paroxysmal nocturnal hemoglobinuria
Pyruvate kinase deficiency
Sickle cell disease (NORD)
Folate (Vitamin B9) deficiency
Vitamin B12 deficiency
Anemia of chronic disease
Iron deficiency anemia
Vitamin K deficiency
Langerhans cell histiocytosis
Essential thrombocythemia (NORD)
Polycythemia vera (NORD)
Acute intermittent porphyria
Porphyria cutanea tarda
Disseminated intravascular coagulation
Von Willebrand disease
Monoclonal gammopathy of undetermined significance
Thrombotic thrombocytopenic purpura
Antithrombin III deficiency
Factor V Leiden
Protein C deficiency
Protein S deficiency
Coagulation disorders: Pathology review
Extrinsic hemolytic normocytic anemia: Pathology review
Heme synthesis disorders: Pathology review
Intrinsic hemolytic normocytic anemia: Pathology review
Leukemias: Pathology review
Lymphomas: Pathology review
Macrocytic anemia: Pathology review
Microcytic anemia: Pathology review
Mixed platelet and coagulation disorders: Pathology review
Myeloproliferative disorders: Pathology review
Non-hemolytic normocytic anemia: Pathology review
Plasma cell disorders: Pathology review
Platelet disorders: Pathology review
Thrombosis syndromes (hypercoagulability): Pathology review
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sideroblastic anemia p. 425
sideroblastic p. 65
ringed sideroblasts in p. 422
sideroblastic anemia and p. 425
in anemia taxonomy p. 423
labs/findings p. 729
lead poisoning p. 425
vitamin B6 deficiency p. 65
With sideroblastic anemia, sidero- means iron and -blastic meaning immature and anemia refers to a condition where there’s a decrease in the number of healthy red blood cells, or RBCs in the body.
So sideroblastic anemia is a type of blood disorder where there’s a buildup of iron in the RBC’s in the body causing them to be immature and dysfunctional.
This buildup occurs because these RBC’s are unable to incorporate iron into hemoglobin which is necessary for RBC’s to transport oxygen.
In order to better understand sideroblastic anemia, we need to first take a look at hemoglobin, the main protein within RBC’s that’s responsible for carrying oxygen.
Now hemoglobin is made up of hemes and globins.
There are 4 globin subunits, typically two alpha and two beta, and each one has its own heme group.
This heme is a large molecule that’s made up of four pyrrole subunits that forms a ring, and this structure is called a porphyrin.
In the middle, there is an ionically bond iron 2+ and the iron is what binds to and carries the oxygen molecule.
So each hemoglobin can carry four oxygen molecules when it’s fully saturated.
The process of heme synthesis occurs both within the mitochondria and the cytosol of a cell and requires multiple enzymes to catalyze the numerous steps.
It begins in the mitochondria where succinyl CoA binds to glycine via delta-ALA synthase which uses vitamin B6 as a cofactor to produce delta-aminolevulinic acid, or ALA.
Then, in the cytosol, delta-aminolevulinic acid is converted to porphobilinogen, or PBG, via delta-ALA dehydratase.
From there, four molecules of porphobilinogen condense together to form hydroxymethylbilane with the help of porphobilinogen deaminase.
Note that porphobilinogen deaminase is sometimes called uroporphyrinogen I synthase or hydroxymethylbilane synthase, or HMBS for short.
Afterwards, hydroxymethylbilane is converted to uroporphyrinogen III and catalyzed to coproporphyrinogen III via uroporphyrinogen III cosynthase and uroporphyrinogen decarboxylase, respectively.
Next, coproporphyrinogen III is brought back into the mitochondria and converted into protoporphyrinogen IX by coproporphyrinogen oxidase.
Protoporphyrinogen IX is converted to protoporphyrin IX by protoporphyrinogen oxidase.
Lastly, an iron molecule is added to protoporphyrin IX via the enzyme ferrochelatase, and 10 tongue twisters later, voila! We got ourselves a completed heme!
Sideroblastic anemia occurs when the bone marrow produces ringed sideroblasts rather than healthy red blood cells (erythrocytes). It is due to either a congenital abnormality or an acquired cause such as vitamin B6 deficiency, excessive alcohol use, or lead poisoning which leads to an inability to incorporate iron to form heme.
The lack of functional heme results in anemia and fatigue. Also, the overload of iron that is unable to be incorporated into RBCs can damage other organs. Diagnosis of sideroblastic anemia involves a medical history and physical examination, along with tests like full blood count and peripheral blood smear. Treatment involves the removal of toxins and the administration of vitamin B6, thiamine, and folic acid.
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