Erythropoiesis Enigmas and Autoimmune Adventures
A 55-year-old man presents with fatigue and pallor. He has a history of chronic obstructive pulmonary disease (COPD) and is found to have a hemoglobin level of 10 g/dL (13.5-17.5 g/dL). His physician explains that his body is likely compensating for chronic hypoxia by increasing the production of erythropoietin (EPO).
Which of the following best describes the primary function of erythropoietin (EPO)?
A) Stimulates red blood cell destruction in the spleen
B) Inhibits production of hepcidin for red blood cell synthesis
C) Stimulates red blood cell production in the bone marrow
D) Increases oxygen binding affinity of hemoglobin
E) Decreases the production of red blood cell precursors
C) Stimulates red blood cell production in the bone marrow
EPO is produced by the kidneys in response to low oxygen levels in the blood, triggered by gene regulation from hypoxia-induced factors. EPO promotes the survival, proliferation, and differentiation of RBCs
Why do reticulocytes stain a deep blue whereas mature erythrocytes exhibit an eosinophilic staining pattern?
APPLICATION - name the different stains used for the staining of of the two cells
Methylene Blue (or other supravital stains) show residual ribosomal RNA/mitochondria in reticulocytes which are necessary for synthesizing hemoglobin (Note - can *technically* use Wright-Giemsa stain for reticulocytes according to first aid but it is better visualized on methylene blue)
The eosinophilic staining exhibited by mature erythrocytes is due to hemoglobin, as shown by Wright-Giemsa staining. Mature RBCs have lost organelles, including ribosomes and RNA, and are filled almost entirely with Hgb.
Intrinsic Factor is produced by...
Gastric parietal cells
Compare/contrast folate deficiency anemia and vitamin B12 deficiency anemia:
homocysteine
methylamalonic acid
homocysteine is increased in both anemias
methylmalonic acid is only increased in vitamin B12 deficiency
What is the prognosis for pernicious anemia?
Potentially reversible, but the neurological damage might be permanent
DOUBLE JEOPARDY! DOUBLE POINTS! WOOOOOO
Where does erythropoiesis normally happen?
THERE IS AN EXCEPTION TO THIS. Explain a condition (hint: issue with RBCs) in which this does NOT happen. Where does erythropoises happen in this case, and why?
Normal - Bone Marrow!
Extramedullary Hematopoiesis/Erythropoises - the production of blood cells outside of the bone marrow, and this typically occurs when there is inadequate production of blood cells for various reasons like in Thalassemia, CML, and other myeloproliferative neoplasms. In these cases, RBC production is forced in the liver, spleen, adrenal glands, pancreas, thyroid, endocardium, testes, uterus, skin, or even the brain
A 65-year-old man presents to the clinic with fatigue, pallor, and recent weight loss. He has a history of chronic kidney disease and diabetes mellitus. A complete blood count shows a hemoglobin level of 9.0 g/dL (13.5-17.5 g/dL) and a mean corpuscular volume (MCV) of 78 fL (80-100 fL). Laboratory tests are performed to evaluate his anemia.
The following results are obtained:
Which of the following is the most likely diagnosis based on these laboratory findings?
A) Iron deficiency anemia
B) Anemia of chronic disease
C) Sideroblastic anemia
D) Thalassemia
E) Megaloblastic anemia
B) Anemia of chronic disease
Serum ferritin is the KEY diagnostic factor here. It is elevated, indicating that iron stores are present. In IDA, ferritin is low because the body is depleted. In ACD, ferritin may be normal/elevated due to inflammation of chronic disease, which increases hepcidin as an acute phase protein (shoutout IL-6) and lowers transferrin as a negative acute phase reactant.
Serum iron is low for both. Low transferrin saturation can occur in both, and TIBC is low. In IDA, TIBC would be high due to increased transferrin production from the body trying to compensate.
A 68-year-old woman presents to her primary care physician with fatigue, weakness, and occasional numbness in her extremities. Laboratory tests reveal macrocytic anemia and elevated levels of methylmalonic acid and homocysteine. The patient has a history of autoimmune gastritis.
Which of the following best explains the mechanism of her vitamin B12 deficiency?
A) Inadequate dietary intake of vitamin B12
B) Impaired secretion of intrinsic factor
C) Increased gastrointestinal absorption of vitamin B12
D) Inhibition of pancreatic proteases
E) Increased binding of vitamin B12 to transcobalamin
Correct Answer B
The patient’s history of autoimmune gastritis suggests that her parietal cells are damaged, leading to a deficiency in intrinsic factor, which is essential for the absorption of vitamin B12 in the ileum. This results in the observed deficiency and its consequences.
A 50 year old woman comes to your clinic. Her chief complaint is painful mouth ulcers. She has fatigue, history of arthritis (she was recently put on methotrexate for her rheumatoid arthritis), and pallor in her mucosal membranes. Her blood smear shows hypersegmented neutrophils. Her blood is drawn, and you see she has a high MCW and low Hb. What is something that could have prevented her symptoms?
Methotrexate inhibits folate metabolism, leading to folate deficiency, which in turn causes megaloblastic anemia. This condition is characterized by macrocytic anemia (high MCV), low hemoglobin (Hb), and the presence of hypersegmented neutrophils on the peripheral blood smear. Fatigue is a common symptom of anemia, along with pallor and other signs like mucosal pallor and mouth ulcers.
Preventative: administering salvage therapy in the form of folic acid or folinic acid (leucovorin)
A 70-year-old woman presents to the clinic with complaints of increasing fatigue, weakness, and numbness in her hands and feet over the past few months. She reports eating a well-balanced diet, and has been feeling more forgetful lately. On physical examination, she demonstrates a wide-based gait and decreased proprioception in her lower extremities. Neurological examination reveals diminished deep tendon reflexes.
Which of the following is the most likely diagnosis for this patient and how can we differentiate between the two best differentials?
A) Folate deficiency
B) Vitamin B12 deficiency
C) Iron deficiency anemia
D) Thalassemia
E) Sideroblastic anemia
The patient’s symptoms of fatigue, weakness, and neurological deficits (numbness, wide-based gait, decreased proprioception) suggest a vitamin B12 deficiency, which can cause neurological symptoms due to myelin damage. While folate deficiency can display similar symptoms, it does not feature the neurological changes like the wide gait and decreased proprioception.
A 42-year-old slightly underweight woman presents to her physician with complaints of generalized fatigue, joint pain, and dry eyes. She has a history of systemic lupus erythematosus (SLE), for which she is being treated with hydroxychloroquine. Laboratory testing reveals the presence of anti-Ro/SSA antibodies, and she is diagnosed with Sjögren syndrome. Over the years, she has also been diagnosed with autoimmune thyroiditis.
Which of the following best explains the development of multiple autoimmune syndromes in this patient?
A) Chronic viral infections
B) A diet high in saturated fat and salt (Western)
C) Interaction of genetic susceptibility and environmental triggers over time
D) Overproduction of pro-inflammatory cytokines
E) Manifestation from long-term medication use
C) Interaction of genetic susceptibility and environmental triggers over time
The development of multiple autoimmune syndromes (MAS) such as SLE, Sjögren syndrome, and autoimmune thyroiditis is explained by a complex interaction of genetic predisposition and environmental factors over a prolonged period of time. For example, various susceptibility genes like HLA and CTLA-4 have been identified in individuals with certain genetic backgrounds to be more susceptible to autoimmune diseases.
BUT, autoimmunity does not develop SOLELY to genetics or SOLELY to the environment. Triggers like infections, hormonal changes, and exposure to toxins can initiate/exacerbate autoimmunity. This gives rise to a progressive evolution of immune dysregulation which will lead to MAS.
What is the Schilling test?
How would the physician apply it to our patient?
It figures out how to determine B12 deficiency
Determines if B12 deficiency is due to malnutrition, malabsorption, bacterial overgrowth, or lack of pancreatic enzymes (chronic pancreatitis).
"Patients ingest radiolabelled B12 and then its urinary excretion is measured. Excretion will be normal if the cause is a dietary deficiency. If excretion is low (suggesting malabsorption), the test is repeated with orally administered intrinsic factor (IF). If excretion normalizes, the cause is IF deficiency. If excretion still remains low, the test is repeated with antibiotics, and then pancreatic enzymes to rule out bacterial overgrowth and pancreatic insufficiency, respectively."
A 55-year-old man presents to the clinic with weakness, numbness, and difficulty walking. Laboratory tests reveal macrocytic anemia and elevated levels of homocysteine and methylmalonic acid. The physician suspects vitamin B12 deficiency due to impaired absorption.
Which of the following biochemical pathways is most directly affected by the lack of vitamin B12 in this patient?
A) Conversion of homocysteine to methionine
B) Conversion of methyl-THF to THF
C) Conversion of succinyl-CoA to heme
D) Conversion of methionine to cysteine
Correct Answer: A
Explanation: The conversion of homocysteine to methionine is directly dependent on vitamin B12 as a cofactor for the enzyme methionine synthase. A deficiency in B12 results in elevated homocysteine levels.
Your patient had his ileum resected five years ago. He shows up to your clinic today. In the context of this PIBL and macrocytic anemias, what symptoms might he have?
The ileum helps absorb vitamin B12
neurologic symptoms, Hashimoto, gastritis, vitiligo, infertility, hyperpigmentation, peripheral neuropathy, pallow, scleral icterus
Explain the treatment for Suzanne and why it is effective
The treatment for Suzanne is intramuscular B12 injections. It is effective because even though it does not address the underlying cause of the lack of B12 absorption, it bypasses the absorption issue through the passive enteral route
A 65-year-old man presents to his physician with complaints of fatigue, shortness of breath, and numbness in his hands and feet over the past few months. He has a history of alcohol use and has been following a strict vegan diet for the past 5 years. Physical examination reveals pallor, glossitis, and diminished sensation to vibration and proprioception in his lower extremities. Laboratory results are as follows:
A peripheral blood smear shows hypersegmented neutrophils and large, oval-shaped red blood cells.
Which of the following cells are most disrupted in this patient?
A) Proerythroblast
B) Orthochromatophilic Erythroblast
C) Extravascular mature erythrocyte
D) Intravascular mature erythrocyte
E) Myeloid progenitor cell
A) Proerythroblast
Patient presents with macrocytic anemia and neuro symptoms, JUST LIKE SUZANNE! Alcohol abuse hints us towards megaloblastic anemia from liver issues storing/releasing B12. Impaired DNA synthesis is critical for early erythroid precursors
A 50-year-old woman presents to her physician with complaints of fatigue, numbness in her feet, and difficulty walking. She follows a "raw" fad diet she saw on Instagram from a pretentious influencer and has not taken any vitamin supplements. On physical examination, she exhibits decreased vibration sense and positive Romberg sign. Laboratory results are as follows:
Further testing shows elevated methylmalonic acid (MMA) and homocysteine levels.
Which of the following additional findings is most likely in this patient?
A) Decreased serum folate from deficiency
B) Significantly low serum haptoglobin
C) Normal neurological exam
D) Elevated lactate dehydrogenase (LDH)
D) Elevated lactate dehydrogenase (LDH)
-Ineffective erythropoiesis leads to massive cell destruction in the bone marrow of cells that are not suitable for maturation. LDH is released from these cells and can eventually get into the bloodstream in addition to the minor lysis that happens, which is why LDH levels are sometimes seen in megaloblastic anemia but SUPER LOW haptoglobin is not often seen.
Everything in the question stem points toward B12 deficiency
A is incorrect because folate deficiencies only cause elevated homocysteine, whereas B12 leads to both elevated MMA and homocysteine.
B - Not fully hemolytic, so there would be less Hgb in the blood from lysis for haptoglobin to bind to.
C - Please reread the question if you thought this was the answer.
A 45-year-old man is evaluated for macrocytic anemia. Blood tests show hypersegmented neutrophils and elevated levels of indirect bilirubin and lactate dehydrogenase (LDH). He reports a history of chronic gastrointestinal issues and has been on proton pump inhibitors for several years.
Which of the following best explains the hematologic findings in this patient?
A) Decreased synthesis of intrinsic factor
B) Ineffective erythropoiesis due to impaired DNA synthesis
C) Increased dietary intake of vitamin B12
D) Enhanced absorption of vitamin B12
E) Decreased production of transcobalamin
Correct Answer: B
Explanation: The patient's macrocytic anemia and hypersegmented neutrophils are indicative of megaloblastic anemia caused by ineffective erythropoiesis due to impaired DNA synthesis from vitamin B12 deficiency. Proton pump inhibitors can lead to decreased gastric acidity, which may impair the release of vitamin B12 from dietary proteins.
An infant arrives in your pediatric private practice. He is one month old. Your attending asks you to look at the growth charts of the patient in EPIC, and you realize he is in 5th percentile for height and weight. His blood smear has hypersegmented neutrophils and macrocytic anemia. Neither folate nor B12 will help him. What is his treatment?
Oral uridine administration, uridine monophosphate, uridine triacetate
Megaloblastic anemia means that blood cell precursors are having trouble dividing in the bone marrow.
Defective synthesis of pyrimidine nucleotides (nucleic acid metabolism), trouble with DNA
UMP synthase converts orotic acid to uridine monophosphate
Accumulation of orotic acid in serum+urine,
Name 4 broad potential causes that can lead to macrocytic anemia (the etiology).
For example, some broad potential causes for normocytic anemia might include aplastic anemia, iron deficiency, autoimmune, HbC, sickle cell, G6PD deficiency, chronic kidney disease, etc.
“Vitamin B12 deficiency, Folate deficiency (only lasts 3 months), Fanconi anemia (Defective DNA repair), Orotic aciduria, Liver disease, Alcohol use, Hypothyroidism, Multiple myeloma, Myelodysplastic syndrome”
Drugs that influence/cause macrocytic anemia:
Phenytoin (impairs absorption of folic acid in small intestine), Sulfa,Trimethoprim (inhibits dihydrofolate reductase), Hydroxyurea, Methotrexate (inhibits dihydrofolate reductase), 6-mercaptopurine (interferes with DNA synthesis)
See presentation
1) Name all the cells, the order in which they appear in erythropoiesis, WHY they appear as they do
2)HIGHLIGHT WHICH STEPS OF MATURATION ARE AFFECTED BY SUZANNE'S CONDITION
See slide
A 32-year-old woman presents to the emergency department with fatigue, shortness of breath, and dark-colored urine. She reports a history of autoimmune thyroid disease and has been experiencing intermittent episodes of jaundice. A complete blood count reveals:
Further laboratory tests are performed, including:
2 part question
1- What anemia does the patient in the vignette have, and what test confirms this - why?
2-Which of the following findings would most likely be seen in a patient with megaloblastic anemia caused by an autoimmune disorder directly compared to this patient?
A) Elevated serum ferritin
B) Reduced reticulocyte count
C) Similar indirect bilirubin
D) Positive direct Coombs test
E) Similar vitamin B12 value
1 - autoimmune hemolytic anemia, confirmed by a direct Coombs test. This test introduces Coomb's reagent to a sample of RBCs and causes them to agglutinate if they have autoantibodies on them.
2 - B) Low reticulocyte count
Low reticulocyte count is the only one that is true out of all options comparatively. While a typically low reticulocyte count is not ALWAYS present in macrocytic anemia (as seen in Suzanne), it is SURELY not HIGH, which is what is seen in autoimmune hemolytic anemia, so we can safely say it will be lower than what we see in the lab values given.
Synthesize a pathway for B12 binding Intrinsic Factor starting with where we obtain B12 and finishing with what B12 is metabolized into
1: B12 is obtained through our diet
2: In the stomach acid, pepsin dissociates B12 from its protein-bound state
3: B12 binds vitamin B12 binding proteins that are secreted in the saliva as it moves to the small intestine
4: Pancreatic proteases cleave the vitamin B12 binding proteins in the duodenum, freeing it to bind IF
5: B12 and IF form a complex that is taken up by the ileum, and it is exported into the bloodstream
6: Cells take up the B12/IF complex by receptor-mediated endocytosis
7: Intracellular B12 metabolized into adenosylcobalamin or methlycobalamin
A patient comes to your clinic with short stature and craniofacial abnormalities. He shows you his thumbs upon the physical. What is his anemia? (Picture of triphalangeal thumb)
Diamond Blackfan Anemia
There is an intrinsic defect of erythroid progenitor cells which leads to more apoptosis.
It's a rare congenital disorder characterized by a failure of the bone marrow to produce red blood cells, leading to anemia. The condition is often caused by mutations in ribosomal protein genes, leading to defects in ribosome function and impaired erythropoiesis.
List the four specific etiologies of vitamin B12 deficiency
Autoimmune: antibodies against intrinsic factor attack it and prevent it from complexing with B12, thereby inhibiting absorption of B12 into the ileum (small intestine)
Malabsorption: Cells in the stomach do not produce intrinsic factor (e.g., gastric bypass), which prevents absorption of B12 into the ileum
Exposure to nitric oxide
Lack of dietary ingestion