Red Viral Rashes

Question 1

Vesicle lesion defn

Answer 1

blister, fluid filled, <1cm

Question 2

Bulla defn

Answer 2

blister >1cm

Question 3

Macule defn

Answer 3

Slightly raised reddened skin rash, <1cm

Question 4

Pustule defn

Answer 4

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

Question 5

Viruses that cause red macular rashes

Answer 5

Measles, Rubella, B19, HHV6,7

Question 6

Viral serology - what are you looking for?

Answer 6

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)

Question 7

Measles virus descriptions

Answer 7

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

Question 8

Classic measles symptoms

Answer 8

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

Question 9

What is the characteristic rash progression of measles?

Answer 9

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

Question 10

Gestational Measles

Answer 10

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

Question 11

Congenital measles

Answer 11

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

Question 12

Measles in the immunosuppressed

Answer 12

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

Question 13

Pathogenesis of measles

Answer 13

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

Question 14

Measles causes immunosuppression

Answer 14

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

Question 15

Immunity to measles

Answer 15

Generally good for life afterwards. ABs last for life.

Question 16

Incubation period and infectiousness of measles

Answer 16

8-12 days incubation. Airborne transmission.

Question 17

Susceptibility to measles

Answer 17

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

Question 18

Complications of measles

Answer 18

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)

Question 19

Tx and prevention of measles

Answer 19

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!

Question 20

Measles vaccine

Answer 20

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

Question 21

Rubella virus description

Answer 21

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

Question 22

Rubella symptoms in children/teens

Answer 22

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

Question 23

Congenital rubella

Answer 23

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

Question 24

Transmission of rubella

Answer 24

Droplet and vertical. Shed lots after 10-18 days

Question 25

Tx and diagnosis for rubella

Answer 25

Clinical. no antiviral.

Question 26

B-19 virus characteristics

Answer 26

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

Question 27

Pregnancy and B-19

Answer 27

High risk of spontaneous abortion.

Question 28

B-19 transmission

Answer 28

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

Question 29

Disease caused by B-19

Answer 29

Usually asymptomatic. Mild rash on face, trunk.

Question 30

Transient aplastic crisis

Answer 30

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

Question 31

B-19 pathogenesis

Answer 31

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.

Question 32

B-19 development

Answer 32

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

Question 33

HHV-6,7 - pathogenesis and name of disease

Answer 33

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

Question 34

HHV-6,7 - progress of disease

Answer 34

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