skin 6: erythema infectious and exanthem subitum Flashcards Preview

Micro > skin 6: erythema infectious and exanthem subitum > Flashcards

Flashcards in skin 6: erythema infectious and exanthem subitum Deck (45):

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?
season? occurs where??


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:


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
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).


5th disease dx

Clinical manifestations


5th dis lab dx

Specific IgG in absence of specific IgM indicates past infection and immunity to disease. IgM is indicative of current infection.
PCR is also possible but is not routine.


5th dis: what will bone marrow biopsy show?

The absence of many erythroid progenitor cells and mature-appearing erythroid cells and the presence of large pink or lilac colored inclusions in giant pronormoblasts and other cells of erythroid lineage


5th dis ddx: ?

for arthropathy: rheumatoid arthritis, and lupus


5th dis tx
if aplastic crisis or fetus with hydrous fetalis?

Antipyretics, analgesics, NSAIDs.
Transfusions for patients in aplastic crisis or fetus with hydrops fetalis (if detected in utero)


Exanthem subitum or Roseola infantum (6th disease, HHV6, HHV-7, HHV-8 infections)

Predominantly HHV-6 and also HHV-7

Herpesvirus 6: HHV-6A and HHV-6B (HHV-6B is the clinically important serotype). Closely related to HHV-7 & HHV-5 cytomegalovirus (CMV).

All are in the  group Herpesviridae. HHV-6 is highly neurotropic.


6th dis: In the same host, different forms of infection occur:

Active, life-long infections in salivary glands
-HHV-6 uses *CD46* as a cellular receptor, a glycoprotein expressed on the surface
of all human nucleated cells
-Persistent, latent infection in macrophages and monocytes


HHV-6 epi

Humans are sole host and reservoir.
Shed in saliva of nearly all adolescents, adults. This is primary mode of transmission.
In utero transmission is rare


Maternal antibodies to HHV-6 appear to prevent infection until ?? when children
become susceptible.

3 to 9 m-o-age


Primary infection with HHV-6 occurs ??

in the first 3 years of life, mostly in the first year

Many primary infections in infants are asymptomatic but some infections may result in s/s
-All children older than 3 years and adults are seropositive for HHV-6. Antibody levels remain high from infancy – probably due to persistence of the organism


HHV-6 is a major cause of ?? in young children

acute febrile illness

Primary HH-6 infection in children 6 to 12 months accounts for approx. 20% of visits to the ER with about 10% of these children hospitalized.


Primary HHV-6 infections also account for ??

*1/3rd of first time febrile seizures, CNS infection, and aseptic meningitis among children


HHV-7 epi

Humans are sole host and reservoir.
Secreted in saliva.
45 - 80% of children 1 to 4 years are HHV-7 seropositive (i.e., later than HHV-6)


HHV-6 Primary infection has a biphasic course;
incubation period ??

Initial febrile phase coincides with the ?? during which virus ??

4-7 days
spreads to and
infects numerous organs and tissue.


HHV-6 Second symptomatic stage is ??
what resolves the virema??
what appears alongside??

immune-mediated NOT INFECTIOUS.
Antibodies resolve the viremia and a rash coincides with appearance of HH-6-specific antibodies and the clearance of HHV-6 via formation of immune complexes (type III hypersensitivity).


Many infants/young children infected with HHV-6 (either asymptomatically or with Exanthem Subitum/Roseola Infantum) develop ??

active (mostly asymptomatic) then life-long, latent HHV-6 infection of the CNS


In immunocompetent persons, HHV-6 virus forms a: ??

-life-long, active infection in the salivary glands.
-latent infection in T-lymphocytes and monocytes.
-persistent infections in probably numerous other cell types?


In immunosuppressed/transplant or AIDS pts, HHV-6 ??

reactivation or re-infection occurs and can lead to severe disease.


Clinical Manifestations of HHV-6, HHV-7 and HHV-8:
primary infection

abrupt onset of high fever (> 38oC), malaise lasting 4 to 6
days. Manifestations can be one or more of the following or none;
Fever, no rash
Macular rash with fever
Mononucleosis-like syndrome


HHV-6, HHV-7: primary infection: Fever, but no rash variety

A common cause of presentation of young children to ERs with high fever and no obvious source is the main reason why spinal taps are done on children.
Fever, lethargy, irritability, possibly even convulsions (signs of meningitis), but an aseptic tap “aseptic meningitis”.
White cells, predominantly lymphocytes and monocytes may be present in CSF.


Macular rash with fever: Exanthem subitum aka Roseola Infantum aka 6th Disease

Macular rash is present in 1/5th of primary infections
-4 days (range is 2 to 5 days) of high fever.
-Rapid defervescence of fever with appearance of a maculopapular rash which lasts 1 to 2 days.
-Rash appears on face and trunk and spreads to limbs; ---
Coincides with rising titers of specific antibodies and elimination of virus from blood, rash resolves spontaneously.


HHV-6, HHV-7: Mononucleosis-like syndrome

in adults
fever, pharyngitis, cervical lymphadenopathy


HHV-6, HHV-7 additional s/s may be present

otitis media (bulging tympanic membrane)
aseptic meningitis
others - gastrointestinal or respiratory distress, hepatitis (FYI)


HHV-6, HHV-7 In immunosuppression (e.g. transplant pt., bone marrow suppression, etc.) what may occur??

pneumonia, encephalitis, hepatitis, rashes. In AIDS pt., pneumonia, encephalitis, retinitis.


Others disease associations with HHV-6, HHV-7, HHV-8

MS – active replication in MS lesions – not known cause but speculation
Additional clinical diseases which may be caused by HHV-7: meningitis,
febrile convulsions, pityriasis rosea.

FYI in utero infection in some pregnancies is likely, Kaposi Sarcoma,
lymphoproliferative and neoplastic disorders


6th dis dx

difficult, especially for exanthem subitum, an IgM EIA is available. IgM for CMV cross reacts with HHV-6 and vice versa


6th dis tx


Decks in Micro Class (61):