3. Viral Exanthems

Question 1

VZV Transmission

Answer 1

• respiratory droplets

- direct contact w/skin lesions

Question 2

VZV Pathogenesis

Answer 2

• infects mucosa of URT
• spreads via blood > skin - papulovasicular rash in crops on trunk & spreads to head & exrtremities (Varecella)
• Multinucleated giant cells w/intracellular inclusions
• infects sensory neurons > DRG via retrograde axonal flow (latent)
• VZV DNA is in nucleus
• reactivated by immunosuppression > painful vesicular skin lesions along course of sensory nerve of head/trunk

Question 3

VZV Lab diagnosis

Answer 3

1-Presumptive: Tzanck smear (multinucleated giant cells)
2- Definitive: cell culture + antiserum
3- Rise in antibody titer (varicella)

Question 4

Coxsackie Virus important properties

Answer 4

RNA virus, Picornavirus family, Enteroviruses

• Small nonenveloped, icosahedral nucleocapsid
• (+ve) ssRNA - viral mRNA
• No polymerase w/ virion & replicate in cytoplasm

Question 5

Coxsackie Virus Transmission

Answer 5

• Fecal-oral

- Respiratory aerosols

Question 6

Coxsackie Virus Pathogenesis

Answer 6

Replicates in oropharynx & GI > bloodstream

Question 7

Group A Coxsackie Virus Diseases

Answer 7

-skin & mucous membranes-

1- Herpangina (fever, sore throat, & tender vesicles in oropharynx)
2- Hand, Foot (vesicular rash) & Mouth (ulcerations) - mainly kids

Question 8

Group B Coxsackie Virus Diseases

Answer 8

1- Pleurodynia (Bornholm disease, epidemic myalgia, “devil’s grip”)
fever & chest pain from intercostal muscle infection
2- Myocarditis & Pericarditis (fever, chest pain, & congestive failure signs)

-B4 plays a role in juvenile diabetes-

Question 9

Group A&B Coxsackie Virus Diseases

Answer 9

1- Aseptic meningitis, mild paresis & acute flaccid paralysis
2- URTI, pharyngitis & minor febrile illness w/w/o rash

Question 10

Coxsackie Virus Lab Diagnosis

Answer 10

1- Isolagting virus
2- Rise in Titer
3- PCR (enteroviral RNA in CSF = viral meningitis)

Question 11

Measles Structure (Paramyxovirus family)

Answer 11

• Lipoprotein w/ spikes of 2 transmembrane glycoproteins
• Helical nucleocapsid
• Nonsegmented Linear +ssRNA
• Single serotype

Question 12

Measles RNA Proteins [3]

Answer 12

1- N Protein
forms helical Nucleocapsid & is major internal protein
2- P (phosphoprotein) & L (large polymerase) Proteins

N-L-P together have RNA-dependent RNA transcriptase activity

Question 13

Measles Envelope Proteins [3]

Answer 13

1- M (matrix) protein
underlies envelope & important for virion assembly
2- Transmembrane Glycoproteins:
-H protein (Hemagglutination & attachment)
-F protein (membrane Fusion + hemolysin activity)

Question 14

Measles Transmission

Answer 14

Respiratory droplets

Question 15

Measles Pathogenesis

Answer 15

URT > blood > reticuloendothelial cells > skin
Rash due to
1- Tc cells killing infected skin endothelial cells
2- Vasculitis

• Multinucleated giant cells are characteristic of lesions
• Binds to macrophagic surface (CD46) suppressing IL-12 production

Causes immunosupression
Life long immunity + maternal antibodies passed on (6 month immunity)

Question 16

Measles Clinical Findings

Answer 16

• Incubation: 10-14 days
• Prodromal phase: fever, conjunctivitis, running nose, & coughing
• Koplik’s spots: bright red lesions w/white central dot on buccal mucosa
• Maculopapular rash: apopears on face > gradually travels down

Question 17

Measles Complications

Answer 17

1- Encephalitis
2- 1ry measles pneumponia & 2ry bacterial pneumonia
3- Bacterial otitis media
4- SSPE: rare fatal disease of CNS, couple years after measles
5- Risk of still birth

Question 18

Measles Lab Diagnosis

Answer 18

1- Clinical Picture
2- Cell culture
3- Fourfold rise of antibody titer
4- PCR