Infectious Anemia Flashcards
What is macrocytic anemia?
Anemia where red blood cells are larger than their normal volume
What is microcytic anemia?
Anemia where you have small, often hypochromatic red blood cells
What is normocytic anemia?
Anemia where you have normal sized red blood cells but a small number of them.
What is Megaloblastic anemia?
A condition in which the bone marrow produces unusually large, structurally abnormal, immature red blood cells (megaloblasts)
What is hemolytic anemia?
Anemia caused by the abnormal breakdown of red blood cells.
What is aplastic anemia?
A rare anemia in which the bone marrow and the hematopoietic stem cells that reside there are damaged. This causes a deficiency of all three blood cell types (pancytopenia): red blood cells (anemia), white blood cells (leukopenia), and platelets (thrombocytopenia).
What is pancytopenia?
A deficiency of all three blood cell types (RBC, white blood cells, thrombocytes)
What is pure red cell anemia (PRCA)?
A type ofanemia affecting the precursors toredbloodcellsbut not white bloodcells. Can be caused by Parvovirus B19 in patients with pre-existing high RBC turnover rates (sickle cell, thalassemia. spherocytosis).
What is autoimmune hemolytic anemia?
When the body’s immune system creates antibodies ( IgG) directed at RBC surface proteins
What are some infectious agents that can cause aplastic anemia?
Hepatitis virus, CMV, EBV and HSV viral infections
How does babesia and plasmodium cause hemolytic anemia?
They directly infect RBC leading to cell lysis.
How does Leishmania cause hemolytic anemia?
Infects the reticuloendothelial system which causes the production of oxidative metabolic products that lyse RBCs.
How does Clostridium perfringens cause hemolytic anemia?
Produces alpha toxin which lyses RBCs.
How does Haemophilus influenza type B cause hemolytic anemia?
The capsular polysaccharide (PRP) binds to the red blood cell surface and anti-PRP antibodies lyse the cell.
What infectious agents can cause autoimmune hemolytic anemia?
EBV, CMV, or HIV infections.
What is microcytic hypochromic anemia associated with?
Microcytic hypochromic anemia (iron deficiency anemia) is caused by blood loss. Infectious agents that can cause this include parasites like hook worm.
What is an infectious agent that can cause megaloblastic anemia?
D. Latum through the accompanying B12 deficiency.
What are the only two known human pathogens in the Parvoviridae?
Parvovirus B19 and Bocavirus.
What is the tropism of parvovirus B19?
Erythroid precursor cells and erythroblasts.
Why must parvovirus B19 infect erythroid precursor cells?
Because it must infect mitotically active cells as it does not encode the means to stimulate cell growth or a polymerase.
What disease does parvovirus B19 cause in children?
Fifths disease/erythema infectiosum.
What disease does parvovirus B19 cause in adults?
Acute aseptic arthritis.
Approximately what percentage of the adult population has been infected with parvovirus B19 by age 40?
65%
What is the target receptor for parvovirus B19?
Erythrocyte P antigen
What is the overview of parvovirus B19 replication?
After binding to the erythrocyte blood group P antigen (globoside) and its internalization, the virion is uncoated, and the single-stranded DNA genome is delivered to the nucleus. Factors available only during the S phase of the cell’s growth cycle and cellular DNA polymerases are required to generate a complementary DNA strand.
What can a chronic parvovirus B19 infection cause in immunocompromised patients?
PRCA Pure red cell aplasia
What can an acute parvovirus B19 infection cause in those with pre-existing high RBC turnover rates? (sickle cell, thalassemia, spherocytosis)
Transient Aplastic Crisis
TAC
Why is hydrops fetalis rare?
Most adult women have antibodies to parvovirus B19 (65% of the adult population infected before age 40)
What is transient aplastic crisis (TAC)?
The abrupt cessation of erythropoiesis characterized by reticulocytopenia, absent erythroid precursors in the bone marrow, and precipitous worsening of anemia
What does a CBC look like in patients with transient aplastic crisis?
- Low reticulocyte count ( 0-1%)
- Drop in hemoglobin levels by 2g/dL
- IgM antibodies by day 3 of illness
- IgG antibodies at time of recovery of erythrogenesis
- PCR will demonstrate high level viremia during TAC
What are two example of hookworms?
Ancylostoma duodenale and Necator americanus
What other symptoms can hookworms cause other than microcytic/ hypochromic anemia?
- vague gastro intestinal complaints
- “ground-itch” rash
- Respiratory symptoms (eosinophilic pneumonitis) due to migration of the larvae
- Pallor, weakness, fatigue, edema
How are hookworms (nematodes) transmitted?
Transmission is by direct penetration of skin by the filariform larvae. Usually through bare feet in fecal contaminated areas.
What is the parthenogenesis of hookworm infection?
Adult worms adhere to mucosa and suck blood which causes iron deficiency anemia due to chronic blood loss.
What is the importance of Vitamin B12 and folate?
They are required for required for thymine synthesis, a building block for DNA
What is megaloblastic anemia characterized by?
Large (macrocytic) & oval red blood cells and low reticulocyte count. Possibly nucleated RBCs in circulation
How does Diphyllobothrium latum cause megaloblastic anemia?
Heavy vitamin B12 uptake by the parasite causes impaired DNA synthesis and normal hemoglobin accumulation.
What are the virulence factors of Haemophilus influenzae B?
- Anti-phagocytic Polyribose Phosphate (PRP) Capsule
- IgA1 protease
What are some differentials for Haemophilus influenzae B?
- Fails to grow on MacConkey agar and BAP.
- V Factor (NAD) requirement
- X factor requirement
- Grows on “Chocolate” agar well
