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35 Cards in this Set

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genus of B19?
erythrovirus
cells in which B19 can propagate?
erythropoietin stimulated erythropoietic cells from bone marrow, umbilical cord blood, or primary fetal liver culture
describe B19's niche for age of infection and seasonality.
bw 5 and 15. late winter and spring
describe seroprevalence of B19.
increases with age, 40 to 60% of adults have Ab's
transmission?
respiratory; schools, hospitals, and parents are susceptable
B19 infects and lyses RBC precursors, why are neutropenia and thrombocytopenia observed clinically?
no one knows...........
describe the biphasic pathogenesis of this bad boy.
7 to 11 days after exposure, pts get flu like symptoms with rhinorrhea during which they are infective via nasopharyngeal shedding. Reticulocyte counts drop but only result in a mild Hb drop. But this is when a ttransient aplastic crisis can occur. Then the immune system kicks in and pts may experience a rash with arthralgia. This is due to the immune response.
what part of the immunity plays a huge role in controlling infection, leading to a restoration of reticulocytosis and a rise in serum Hb?
humoral immunity, B19 IgM appears in 2 days followed by IgG.
who is at risk for chronic B19 infections.
those with impaired humoral immunity such as children on chemo, congenital immunodeficiency states, transplant patients, and those with AIDS
describe B19 in fetuses and neonates.
nonimmune fetal hydrops and still birth usually from CHF is most serious case, but most infections during pregnancy result in normal deliveries and asymptomatic children with no teratogenic effects
symptoms of B19 infection in children? adults?
kids get erythemia infectiosum while adults, esp. women, get acute arthropathy with or without the slapped cheeks
describe the three phases of the rash in 5ths disease.
initial is facial flushing with typical slapped cheeks. then spreads to trunk and proximal extremities as a diffuse macular erythema. central clearing occurs promptle giving it a lacy appearance and the palms and soles are spared
what are some types of chronic hemolysis that are susceptable to transient aplastic crisis from B19?
sickle cell, thalassemia, hereditary spherocytosis, and pyruvate kinase deficienct.
signs and symptoms of profound anemia?
pallor, tachycardia, and tachypnea (hyperventillation). note sickle cell patients may have a pain crisis
B19 induced myocarditis is seen in what populations?
all ages but it is rare, note that infants are known to have the viral receptor on their myocardial cells.
describe the dermatologic syndrome sometimes associated with B19 infection.
papular-purpuric glove and socks syndrome. fever, pruritus, and painful edema and erythema localized to the distal extremities in a distinct glove and sock distribution followed by acral petechiae and oral lesions.
describe how B19 is diagnosed in all populations.
usually the presence of rash or transient aplastic crisis in a sickle cell patient is diagnostic. Serology can be performed (IgM for acute and IgG for past infection). Immunocompromised patients need PCR or hybridization as serology is not accurate in them. fetal hydrops caused by B19 can be confirmed by PCR or hybridization from fetal blood
differentials?
rash: rubella, measles, enteroviral infections, and drug rxns. Rash and arthritis in older children: RA, SLE, and other connective tissue disorders
treatments?
no specefic treatments, symptomatic. Immunocompromised should quit being immunocompromised if they can (like stop the chemo for a bit or quit the steroids), IgG infusions may help in AIDS or inherited immune deficiencies. diagnosis of fetal hydrops should be reffered to fetal therapy centers, some can be treated with a intrauterine transfusion but serious complications can arise
should anyone be isolated when 5ths disease is about?
once the rash appears, the virus is not contagious, but if it is going around at school, pregnant women should lay low. those with transient aplastic crises ARE contagious (get symptoms with viremia) and thus should be isolated.
can the rash re-appear?
yes, for weeks to months, it can fluctuate its intensity and is recur with changes like temperature and sunlight
brief description of the parvovirus structure and morphology...
nonenveloped, ssDNA, replicates only in human erythrocyte precursors
modes of transmission?
resp tract secretions, blood exposure, vertical transmission
in what stage of infection is papulopurpuric gloves and socks syndrome seen?
during viremia, thus they are infectious when symptomatic
how long should aplastic crisis patients be isolated?
til one week after symptoms go away
incubation period?
4 to 21 days (usually around 15)
random fact\discrecpancy between articles:
the red book says that bc EI is common in the community and not just isolated to something like a school outbreak and that fetal complications if infected are slim, pregnant women should not be excluded from the work\school environment.
how "hardy" is the virion.
pretty tough bc it is not enveloped thus it can remain in the environement for a while
describe the possible outcomes of an aplastic crisis.
usually self limiting but can cause severe, occasionally fatal, anemia that preceipitates CHF, CVAs, and acute splenic sequestration
what specefic part of the immune response is probably responsible for the rash in 5th disease?
Ag-antibody complexes
what does the marrow look like in infected individuals?
no mature erythroid precursors but giant pronormoblasts are present
why does parvovirus infect the fetal liver?
it is the site of early erythrocyte production
what is the risk of infection during pregnancy and the following risk of fetal loss?
30% chance of infection with a 5 to 9% risk of fetal loss
what is the cell receptor for B19?
globoside (erythrocyte P antigen), found on erythrocyte precursors, placenta, and fetal myocardial cells
infection incurs what kind of immunity?
life long immunity