Red Viral Rashes Flashcards Preview

Med Triple I > Red Viral Rashes > Flashcards

Flashcards in Red Viral Rashes Deck (34):

Vesicle lesion defn

blister, fluid filled, <1cm


Bulla defn

blister >1cm


Macule defn

Slightly raised reddened skin rash, <1cm


Pustule defn

pus filled blister deep under skin, painful, <1cm


Viruses that cause red macular rashes

Measles, Rubella, B19, HHV6,7


Viral serology - what are you looking for?

Look for convalescent increase in AB - must be 4 fold (ie 1/2 to 1/32 dilution). Take before and then after (ie two weeks apart)


Measles virus descriptions

Rubeola. -ssRNA. Only one serotype, only in humans. Not latent or persistent. Two surface glycoproteins (H and F), M protein under envelope


Classic measles symptoms

Fever, malaise, anorexia, conjunctivitis, photophobia, myalgia. Koplik’s spots (appear on buccal mucosa: gray or other spots diagnostic of measles prior to rash). Characteristic rash. Intense inflammation of lymphoid tissue and mucosa of the respiratory tract. Tracheobronchitis and pneumonia common


What is the characteristic rash progression of measles?

Maculopapular rash, behind ears, then face, upper arms and trunk, then legs by 3rd day.


Gestational Measles

risk of pneumonia during the 3rd trimester. No fetal abnormality but premature delivery and spontaneous abortion


Congenital measles

Rash present at birth or in first 10 days. Mortality 30%


Measles in the immunosuppressed

Severe, frequently fatal often no rash (b/c no immune system!). Giant cell pneumonia (syncytia). Sub-acute encephalitis: mortality >85%


Pathogenesis of measles

Cellular receptor is CD46 (C3b binding protein on many cells). Infection of vascular endothelial cells causes increased permeability and edema. Formation of multi-nucleated cells (F protein), syncytia with inclusion bodies in host cells – results in host cell death (necrosis), can lead to more bacterial infections


Measles causes immunosuppression

Lasts several weeks after rash. Virus infects Dendritic cells and monocytes. Circulating T cells decreased. Cytokine response is thrown off so you increase TH2 more when you need TH1, less macrophage activity


Immunity to measles

Generally good for life afterwards. ABs last for life.


Incubation period and infectiousness of measles

8-12 days incubation. Airborne transmission.


Susceptibility to measles

Male, pregnant or malnourished. Much more lethal in developing countries.


Complications of measles

Otitis media, pneumonia, diarrhea, encephalitis most common. Keratitis in kids with vit A deficiency (corneal ulceration and blindness). Secondary bacterial infections. Acute post-infectious encephalitis is the most common neurological complication of measles. SSPE: sub-acute sclerosing panencephalitis – rare delayed complication, presents 6-8 years after, fatal in 1-3 years)


Tx and prevention of measles

Isolate cases to prevent spread. Tx is symptomatic: bed rest, hydration, antipyretics, vitamin A. No good antiviral. Passive immunoprophylaxis with Ig for contacts is doable. Vaccination is key!


Measles vaccine

95% effective. Combined measles, mumps, rubella and varicella vaccine (MMRV): First dose at 12-15 mo, Second dose at 4-6


Rubella virus description

aka German measles. Enveloped virus. 1 serotype, human only. E1 (hemagglutinin), E2 glycoproteins. Concern is over effects on fetus.


Rubella symptoms in children/teens

Usually rash with no warning in kids. Adults and adolescents 1-5 days prodrome. Lymphadenopathy, conjunctivitis, other classic symptoms. Erythematous maculopapular rash appears after 16 days, first on face then spreads to trunk and extremities. Rash lasts 3 days


Congenital rubella

Severe effects on child. 80% deafness. If mother is infected it is very likely. The earlier in pregnancy the worse the defects


Transmission of rubella

Droplet and vertical. Shed lots after 10-18 days


Tx and diagnosis for rubella

Clinical. no antiviral.


B-19 virus characteristics

Parvovirus. aka “slapped cheek syndrome/erythema infectiosum/5th disease”. Non enveloped ssDNA virus. only in humans. Common in kids, but usually ok. Tropism for erythrocytic precursors. No vaccine


Pregnancy and B-19

High risk of spontaneous abortion.


B-19 transmission

can be transmitted vertically from mother to fetus, or by the respiratory routes and by transfusions. Possibly direct contact or droplet


Disease caused by B-19

Usually asymptomatic. Mild rash on face, trunk.


Transient aplastic crisis

Caused by B-19. Lytic infection of RBC precursors, temporary shutdown of RBC production. Can cause anemia, most serious in fetus.


B-19 pathogenesis

B-19 requires actively dividing cells (needs cellular functions expressed only during S phase). B19 attaches to host cells by means of the P antigen.


B-19 development

Fever for 5-7 days, rash 15-17 days.


HHV-6,7 - pathogenesis and name of disease

Replicates in CD4+ cells, NK cells. Causes roseola aka exanthema subitum in infancy


HHV-6,7 - progress of disease

Abrupt high fever (to 40°C) lasting 2-3 days. Drop in temperature coincides with rash. Rash lasts 1-2 days. Drowsiness, irritability. Rash first on neck, behind ears and back, then spreads to scalp and torso. 2-7 days illness