Micro: Viral Exanthems

Question 1

What are some descriptors for viral exanthems?

Answer 1

morbilliform = measles like rash - erythematous macules and papules
scarlatiniform = scarlet fever like rash - pinpoint sandpapery papules

Question 2

What are some suspicious clues that can suggest a viral etiology for a rash?

Answer 2

spring or summer onset
kids > adults
petechial or vesicular component

Question 3

What is the microbiology of measles?

Answer 3

ssRNA, nonsegmented, helical nucleocapsid
morbillivirus of family paramyxoviridae (parainfluenza, RSV, Measles, Mumps)
enveloped, 1 serotype

Question 4

How is the measles virus transmitted?

Answer 4

respiratory droplets, direct contact w nose or throat secretions of infected person
incubation = 7-8 days preceding rash, highly contagious from 1st respiratory symptoms - 4 days after rash onset

Question 5

What is the pathogenesis of measles?

Answer 5

infects epithelial cells in URT - primary multiplication - enters bloodstream and spreads to reticuloendothelial cells - replicates again - secondary viremia –> inf of WBCs (monocytes), spread to skin and respiratory tract = febrile prodrome
infected cells become multinucleated giant cells w inclusion bodies in nucleus and cytoplasm

Question 6

What are the disease manifestations of measles?

Answer 6

three C’s = cough, conjunctivitis, coryza
febrile prodrome, then Koplik spots (small blue and white spots w bright red background on buccal mucosa) and morbilliform rash (cephalo-caudal spread) - whole body involved in 3 days, fades in 3-4, lasts 6-7
rash may have transient petechiae and purpura
Ag-Ab complex vasculitis

Question 7

How does measles resolve?

Answer 7

faint post-inflammatory hyperpigmentation
leukopenia
acquired immunity after natural inf is permanent
if defective cell immunity (HIV) can progress to giant cell pneumonia, otitis media and subacute sclerosing panencephalitis (yrs later)

Question 8

How is measles diagnosed?

Answer 8

isolation from clinical specimens or serology - syncytial keratinocyte giant cells
presence of specific IgM indicates acute, more than 4x increase in IgG indicates recent inf
Ab-capture IgM assay highly sensitive and specific

Question 9

What is the treatment and prevention of measles?

Answer 9

treatment is supportive
immunization - 2 dose MMR, live attenuated viruses
contraindicated in immunosuppressed, pregnant
immunization w/i 72 hrs of exposure may proved post exposure protection

Question 10

What is the microbiology of rubella?

Answer 10

togavirus family, enveloped

ssRNA, 1 serotype

Question 11

How is rubella transmitted?

Answer 11

droplet spread or direct contact

transplacental can result in congenital rubella syndrome

Question 12

How is the rash of rubella different than measles?

Answer 12

distribution is the same
lesions less intensely red, “blueberry muffin” lesions
exanthem spreads quicker, w/i 24 hrs
enanthem has characteristic petechiae in mouth

Question 13

What is the pathogenesis of rubella?

Answer 13

same as measles:

virus specific T cells attack vascular endothelial cells, vasculitis, rash follows prodromic febrile stage

Question 14

What is the timing of rubella?

Answer 14

infected shed virus 1 week before and 2 weeks after rash

rash appears 14-17 days post exposure

Question 15

What can infection w rubella during pregnancy cause?

Answer 15

death, miscarriage
congenital rubella syndrome: sensorineural deafness, mental retardation, eye abnormalities, congenital heart dz (PDA), dermal hematopoiesis

Question 16

What is the treatment and prevention for rubella?

Answer 16

same as measles

Question 17

How is rubella diagnosed?

Answer 17

isolation of virus from sample or serology
specific IgM for acute, 4 fold increase IgG for recent
amnio and culture for pregnant women
IgM between 2 wks - 3 mos after birth for congenital

Question 18

What is the microbiology of parvovirus B19 (erythema infectiosum)?

Answer 18

parvoviridae family, no envelope, small ssDNA
replicates in erythroid progenitor cells
more common in kids, most adults are seropositive

Question 19

How is parvovirus B19 transmitted?

Answer 19

respiratory droplets, direct contact w secretions, percutaneous exposure to blood or blood products, vertical transmission
winter-spring epidemics
household contact spread very common
erythema infectiosum most contagious before rash onset

Question 20

What are the disease manifestations of erythema infectiosum?

Answer 20

prodrome: nonspecific, child not that sick

rash has 3 phases: slapped cheek, reticular rash on trunk and limbs, intermittent flare from environmental stimuli

Question 21

What are the possible complications of parvovirus?

Answer 21

hemolytic anemias - can cause crisis in sickle cell or chronic anemia due to further halting of RBC maturation
immunocompromised can get chronic anemia or pneumonia
during pregnancy - hydrops fetalis, growth retardation, effusions, death
papular-purpuric gloves and socks syndrome = symmetric, rapidly progressive, sharp demarcation at wrists and ankles

Question 22

How is parvovirus B19 diagnosed?

Answer 22

IgM specific, four fold rise in IgG
PCR based viral nucleic acid detection test
bone marrow biopsy if pt develops aplastic anemia shows arrest only at proerythroblast stage

Question 23

What is the treatment and prevention of parvovirus B19?

Answer 23

no treatment for immunocompetent, IVIG for chronic anemia and immunocompromised
children excluded from school while fever present, not infectious if cutaneous findings present
exanthem of PPGSS still infectious

Question 24

What is the microbiology of roseola infantum?

Answer 24

due to HHV 6 and 7 inf, beta herpesvirinae
linear dsDNA, enveloped and sensitive
can re-activate in immunosuppressed
HHV-6 - almost all children seropositive by age 5
HHV-7 - almost all US adults seropositive
replicate in nucleus, cytopathic for T cells

Question 25

How is roseola infantum transmitted?

Answer 25

respiratory secretions
virus latent in lymphocytes and salivary gland
children most likely to get acute inf

Question 26

What is the prevention of roseola infantum?

Answer 26

no vaccine, inf results in immunity

Question 27

What are the disease manifestations of roseola infantum?

Answer 27

mild illness in kids, high fever in otherwise well infant

after fever: pink erythematous papules and macules on trunk and spreading outwards, lasts 1-3 days (quick)

Question 28

What are differentiating features among the different rashes present w these viruses?

Answer 28

measles - cephalo-caudal, takes 3 days
rubella - cephalo-caudal, takes 24 hrs
erythema infectiosum - “slapped cheek”
roseola infantum - spreads from trunk out, 1-3 days

Question 29

What are possible complications of roseola infantum?

Answer 29

latency in mononuclear cells
reactivation of HHV-6 in immunosuppressed
drug hypersensitivity syndrome = reactivation due to drugs
lymphoproliferative dzs, pityriasis rosa?

Question 30

How is roseola infantum diagnosed?

Answer 30

serology, cultures, immunohistochemistry, PCR

Question 31

What is the treatment of roseola infantum?

Answer 31

usually just supportive
antivirals for encephalitis (NOT acyclovir)
reduction of immunosuppression if possible

Question 32

What is the microbiology of VZV?

Answer 32

same as herpes, except single serotype

characteristic eosinophilic intranuclear inclusions and multinucleated giant cells

Question 33

What are the disease manifestations of VZV?

Answer 33

varicella zoster = chicken pox
herpes zoster = shingles
lesions have several stages of maturity at same time

Question 34

What are possible complications of reactivation of VZV?

Answer 34

dissemianted herpes zoster w generalized skin eruption
pneumonia: more in adults and immunosuppressed
encephalitis
Reye’s syndrome (2nd most common after flu)
Staph or GABHS superinfection most common
congenital if mom pregnant - atrophy and hypoplasia
neonatal if close to birth - high mortality

Question 35

How is VZV transmitted?

Answer 35

late winter-early spring
inhalation of respiratory aerosol, virus in skin lesions not contagious
contagious 1-2 days before rash- 5 days after

Question 36

How is VZV diagnosed?

Answer 36

usually clinical
complicated inf: virus from skin lesions, Tzanck smear, DFA shows viral antigen in fluid, PCR, viral culture not routinely used

Question 37

What is the treatment for VZV?

Answer 37

acyclovir and newer versions

oral therapy not helpful once lesions have already crusted

Question 38

What is the prevention of VZV?

Answer 38

Varivax in children - if breakthrough dz due to waning immunity, still less severe
VZIG via IM w/i 96 hrs of exposure in high risk
Zostavax - 10x more virus than Varivax, reduces zoster in ELDERLY by 50%

Question 39

What is the microbiology of enteroviruses?

Answer 39

small ssRNA, Picornavirus family (echovirus, coxsackie, enterovirus, poliovirus)
found in respiratory secretions or stool

Question 40

What illnesses has enterovirus been implicated in?

Answer 40

hand foot and mouth dz (HFMD)
herpangina
hemorrhagic conjunctivtis
HSP
papular acrodermatitis
eruptive psuedoangiomatosis

Question 41

What are the clinical manifestations of HFMD?

Answer 41

prodrome
self-limited exanthems, painful enanthem of vesicles and erosions
supportive treatment

Question 42

What are the clinical manifestations of herpangina?

Answer 42

characteristic enanthem of painful vesicles and erythematous erosions on palate, uvula, tonsils
self limited

Question 43

How is enterovirus transmitted?

Answer 43

person to person: fecal-oral or respiratory

infect epithelial tissue, replicate in lymphoid tissues, spread viremically