skin 6: erythema infectious and exanthem subitum Flashcards
Erythema infectious (5th disease) - Human parvovirus B19 infection
self-limited, rash-producing disease of childhood but causes more severe manifestations later in life.
Human parvovirus B19
has a very strong predilection for ?? and ??
Parvovridae; Human Parvovirus B19.
Small, ssDNA, non-enveloped virus with one serotype.
This and the bocavirus are the only parvovirus known to infect humans.
bone marrow and erythrocyte precursors in particular
Erythema infectiosum: common?
host?
season? occurs where??
POE??
common childhood disease
Humans are the only host; 1⁄2 to 3⁄4 of all adults are seropositive
-Late winter and spring peak incidence. It occurs in outbreaks in schools and daycare centers and has been known to shut down whole schools.
-POE is likely the URT via respiratory secretions, respiratory droplets.
Erythema infectiosum: age distribution??
what about secondary arthropathy?
Erythema infectious in 4-15 yos, arthropathy is uncommon, less than 10% of cases
Arthropathy: Adults, especially women. Secondary infection - type III hypersensitivity reaction; immune complex deposition
Erythema infectious: pathogenesis is ??
initial phase:
biphasic
Fever and infectious.
5th dis: Initial replication - ??
then a viremia around day ??
what causes constitutional symptoms??
RT, High viral titers are present in oral and respiratory secretions then a viremia around day 8 – The immune response causes constitutional symptoms.
5th dis: ?? stops for about 1 week as virus infects ??, where it kills ??
Results in ??
Erythrocyte production stops for about 1 week as virus infects bone marrow cells, where it kills erythroid precursor cells.
sub-clinical anemia or even aplastic crisis depending on immune status
5th dis: Second/symptomatic stage: ??
what coincides with appearance of Abs??
Immune mediated - not infectious.
Antibodies resolve disease.
Rash, arthralgia coincide with appearance of HPV B19-specific antibodies and
disappearance of HPV B19 from blood via formation of immune complexes (type III hypersensitivity).
5th dis: Prodrome (Initial stage): mild symptoms that persist for 2 to 3 days and include:
General flu-like symptoms
Some respiratory symptoms
Sometimes nausea, vomiting, abdominal pain.
typically the fever defervesces and other symptoms subside.
after the 5th dis prodromal fever defervesces and other symptoms subside what appears ??
Rash Stage (Secondary stage): A erythematous maculopapular (lacy appearing) rash manifests briefly (fever may be absent)
Rash Stage (Secondary stage):
Initially on the face, a “slapped-cheek appearance” with relative circumoral (around the mouth) sparing.
- May also involve the limbs, less commonly the trunk,
- May involve the palms and soles (socks and gloves).
- May be pruritic
- Usually resolves in 2 to 3 days.
The 5th dis rash can be exacerbated by ??
exercise, emotion, hot baths, or sunlight.
The intensity and distribution of the rash varies.
The rash can be difficult to appreciate in dark-skinned individuals and to distinguish from other viral exanthems, such as rubella.
5th disease in adults
viral syndrome with fever and arthropathy. The rash is less common, principally have Arthropathy and other rheumatic (rheumatoid) manifestations including vasculitis
5th disease in adults: Upon primary infection with HPV B19:
flu-like symptoms that persist for 3 to 4 days
- then polyarthralgia and symmetric polyarthropathy – with or without fever
- joints involved are:
i. hands and wrists (mostly),
ii. knees
iii. ankles - arthropathy is usually self-limiting, lasting 2 to 3 weeks, but can be prolonged (months)
5th disease: complications
Aplastic crisis:
Risk factors are concurrent:
Chronic hemolytic anemia SCD Acquired anemia Chronic hemolysis Any person with underlying conditions that stresses the bone marrow can manifest with a transient aplastic crisis (severe anemia/reticulocytopenia)
clinical manifestations aplastic crisis (5th dis)
Clinical manifestations: severe anemia for 7 to 10 days
-Dyspnea, Fatigue, Malaise, Confusion
-Maculopapular rash, polyarthropathy, arthralgia, may also occur
-the anemia may be protracted in immunocompromised patients who
are unable to control the infection
-Chronic bone marrow failure may occur which can be fatal
5th dis. aplastic crises in pregnant women
no adverse effects on the mother, but during the
- 1st trimester may result in still birth.
- 2nd trimester may lead to destruction of erythrogenic precursors, causing fetal anemia and congestive heart failure (fetal hydrops) and fetal death.
- 3rd trimester may result in non-hydropic fetal death.
5th dis. Immunity
Antibody mediated. Reinfections are possible in adulthood and will likely manifest as arthropathy or anemia syndromes described above. The main pathological mechanism for the arthropathy is likely to be a type III hypersensitivity reaction (immune complex-mediated).
