Red Viral Rashes Flashcards Preview

Med Triple I > Red Viral Rashes > Flashcards

Flashcards in Red Viral Rashes Deck (34)
Loading flashcards...
1
Q

Vesicle lesion defn

A

blister, fluid filled, <1cm

2
Q

Bulla defn

A

blister >1cm

3
Q

Macule defn

A

Slightly raised reddened skin rash, <1cm

4
Q

Pustule defn

A

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

5
Q

Viruses that cause red macular rashes

A

Measles, Rubella, B19, HHV6,7

6
Q

Viral serology - what are you looking for?

A

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)

7
Q

Measles virus descriptions

A

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

8
Q

Classic measles symptoms

A

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

9
Q

What is the characteristic rash progression of measles?

A

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

10
Q

Gestational Measles

A

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

11
Q

Congenital measles

A

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

12
Q

Measles in the immunosuppressed

A

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

13
Q

Pathogenesis of measles

A

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

14
Q

Measles causes immunosuppression

A

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

15
Q

Immunity to measles

A

Generally good for life afterwards. ABs last for life.

16
Q

Incubation period and infectiousness of measles

A

8-12 days incubation. Airborne transmission.

17
Q

Susceptibility to measles

A

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

18
Q

Complications of measles

A

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)

19
Q

Tx and prevention of measles

A

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!

20
Q

Measles vaccine

A

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

21
Q

Rubella virus description

A

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

22
Q

Rubella symptoms in children/teens

A

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

23
Q

Congenital rubella

A

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

24
Q

Transmission of rubella

A

Droplet and vertical. Shed lots after 10-18 days

25
Q

Tx and diagnosis for rubella

A

Clinical. no antiviral.

26
Q

B-19 virus characteristics

A

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

27
Q

Pregnancy and B-19

A

High risk of spontaneous abortion.

28
Q

B-19 transmission

A

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

29
Q

Disease caused by B-19

A

Usually asymptomatic. Mild rash on face, trunk.

30
Q

Transient aplastic crisis

A

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

31
Q

B-19 pathogenesis

A

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.

32
Q

B-19 development

A

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

33
Q

HHV-6,7 - pathogenesis and name of disease

A

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

34
Q

HHV-6,7 - progress of disease

A

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