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Pathology > SPR L1 Childhood Exanthems and Selected Skin Manifestations > Flashcards

SPR L1 Childhood Exanthems and Selected Skin Manifestations Flashcards

1
Q

What is an Exathem?

A

A skin rash

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2
Q

What do the following agents cause?

  1. HSV
  2. Varicella
  3. Enterovirus
  4. Erythrovirus B19
  5. Measles Virus
  6. Rubella Virus
A
  1. Vesicular Lesions
  2. Chickenpox shingles
  3. Rashes
  4. Rash
  5. Measles
  6. Rubella
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3
Q

Childhood exanthems - what are the key agents?

A

HSV

Varicella

Enterovirus

Erythrovirus B19

Measles Virus

Rubella Virus

+ arthropod infestations (lice, mites, myiasis

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4
Q

Learning Outcomes

A
  • Describe herpes simplex and varicella infections
  • Describe the epidemiology and clinical aspects of the common childhood exanthems (enterovirus rashes, erythrovirus B19, measles, rubella)
  • Briefly describe arthropod skin infections.
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5
Q

Which agents cause vesicular skin lesions?

A

HSV and Varicella

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6
Q

Which agents cause exanthems?

A

enterovirus rashes, erythrovirus B19, measles, rubella

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7
Q

What are the subfamilies of Herpes?

A
  • Alpha-herpesvirus
    • HSV-1
    • HSV-2
    • VZV
  • Beta-herpesvirus
    • CMV
  • Gamma-herpesvirus
    • EBV
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8
Q

Herpes simplex virus (HSV)

  1. ​When is it acquired?
  2. Describe it’s size
  3. What are the two types?
  4. How are they distinguishable?
  5. What is the basic lesion seen?
  6. How is the infection transmitted?
A
  1. Mostly in early childhood
  2. medium-sized (120 nm), double-stranded DNA
  3. HSV1 (oral and genital infections) and HSV2 (genital infections)
  4. distinguishable antigenically.
  5. Intraepithelial vesicle
  6. from the saliva or cold sores of other individuals.
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9
Q

HSV infection

  1. Where does the virus replicate?
  2. Outline what happens during the primary infection (e.g. gingivostomatitis)?
  3. Where does the latent virus remain?
  4. What happens when the lesion resolves?
A
  1. in oral mucosa/skin - virus rich VESICLES
  2. virus enters sensory nerve endings

–transported to the dorsal root (trigeminal) ganglion

–latent infection in sensory neurones

  1. In the sensory ganglion.
  2. antibody / CMI responses develop.

latent virus remains in the sensory ganglion for life,

& can reactivate (2ndry infection) to cause cold sores.

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10
Q

HSV

Where can a primary and secondary infection occur in , give examples?

A
  • the eye
    • conjunctivitis and keratitis, often with vesicles on the eyelids
  • the finger
    • herpetic whitlow
  • other skin sites
  • the genital tract

(see previous STI lecture)

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11
Q

Give examples of some complications associated with HSV

A
  • Eczema herpeticum
    • herpetic infection of eczematous skin areas leading to severe disease in young children
  • acute encephalitis (in CNS lecture)
    • following either primary infection or reactivation
  • neonatal infection acquired from the genital tract of the mother
  • immunocompromised individuals
    • very severe disease
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12
Q

What can HSV reactivation be provoked by?

A
  • febrile illnesses
    • (e.g. common cold, pneumonia)
  • direct sunlight (UV)
  • stress
  • trauma
  • ?menstruation
  • immunocompromise.
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13
Q

What is a sensory prodrome?

A

A sensory prodrome in the affected area (feeling pins and needles, pain, burning, and itching) precedes the appearance of the coldsore

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14
Q

HSV Treatment

  1. What is the main treatment?
  2. How does it act, what is a benefit?
  3. What are the alternatives?
  4. When must the main drug be given IV?
A
  1. Aciclovir, Oral or IV, or supression (continuous low dose)
  2. acts specifically in virus-infected cells - Because Viral Thymidine kinase activates the drug, so it is well tolerated
  3. valaciclovir (valine ester of aciclovir), famciclovir (modified aciclovir with a longer half life)
  4. for encephalitis or disseminated HSV infection

& in immunocompromised individuals..

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15
Q

HSV Diagnosis

How can HSV be diagnosed?

A
  • Direct detection in lesion
    • PCR - Most sensitive
    • Older methods = Culture antigen detection, Less sensitive
  • Serology
    • IgM
    • IgG
    • Type specific serology
  • Or real time detection using a fluorescent probe
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16
Q

Varicella Zoster Virus

  1. What does the primary infection give rise to?
    1. What is the incubation period?
  2. What does reactivation give?
    1. When can it occur?
    2. How can it be age related?
A
  1. Chickenpox, very infectious. (94% adults in NI are immune)
    1. 14-16 days
  2. Zoster (shingles).
    1. Years/decades after
    2. loss of cell mediated immunity to varicella with age
17
Q

Describe some lesions that may appear with Varicella

A
  • Macule - flat
  • Papule - raised edge you can feel
  • Vesicle - inside of papule is fluid filled
  • Pustule - material inside is cloudy
18
Q

What are the Key Complications of Varicella?

A
  • Pneumonia - primary varicella, Secondary bacterial pneumonia can also occur
  • CNS Involvement - Lymphocytic meningitis, Encephalitis
  • Primary infection during pregnancy
19
Q

Zoster - Reactivation

  1. What are the main characteristics?
  2. What is a common complication in elderly patients?
  3. What are the factors predisposing to zoster?
A

1.

  • Dermatome distribution
    • somatic
    • trigeminal
  • Thoracic dermatomes most common
  • Paresthesia and pain
    • erythematous rash -> vesicles
      • fever and malaise.
  1. Post zoster neuralgia (pain)

3.

  • Increasing age.
  • Immunocompromise
  • Trauma or tumors affecting the brain or spinal cord
20
Q

Diagnosis of Chickenpox and Zoster

​What are the main methods of diagnosis?

A
  • Mainly clinical diagnosis
  • Direct detection
    • PCR
    • Or other methods: immunofluorescence antigen detection , virus isolation, electron microscopy on vesicle fluid
  • Serology
    • VZV IgG (immunity testing)
    • VZV IgM (recent infection:positive day 5 of rash)

In practice only PCR is used

21
Q

VZV Treatment

  1. What is the treatment?
  2. Outline the vaccine
A
  1. Similar to HSV but Acyclovir needs used at higher dose than for HSV
  2. live attenuated vaccine

licensed in a number of countries

universal childhood immunization in USA since 1995

Not in UK so far

22
Q

Enteroviruses (picornavirus family)

  1. Name two viruses this family includes
  2. What do they give rise to?
  3. Who does it affect?
  4. What else can these viruses be responsible for?
  5. What is Hand Foot and Mouth usually caused by?
A
  1. coxsackie and echoviruses
  2. a variety of exanthems (Maculopapular rashes in summer)
  3. young children mostly
  4. illnesses affecting the CNS, URTI and occasionally heart muscle
  5. Coxsackie A16
23
Q

Erythrovirus B19

  1. What type of virus is this?
  2. What does it cause?
  3. How is it spread?
A
  1. Parovirus - very small (22 nm diameter) ss DNA
  2. Febrile illness in children & maculopapular rash on face (‘slapped cheek syndrome’), AKA ‘erythema infectiosum’ or ‘fifth disease‘ - Symptomless infection is common
  3. respiratory droplets
24
Q

B19 - Complications

  1. Where does it B19 grow?
  2. What does this lead to?
  3. What can the virus cause when it affects adults?
  4. What can it cause when an in utero infection?
A
  1. hemopoietic cells in the bone marrow
  2. temporary fall in hemoglobin levels, BUT can lead to serious consequences in those with chronic anemia associated with reduced RBC lifespan. E.g sickle cell anemia (aplastic crisis can occur)
  3. arthralgia
  4. Hydrops fetalis
25
Q

B19 - Diagnosis

How is it tested for?

A
  • erythrovirus B19-specific IgM.
  • PCR on blood
  • IgG immunity testing
    • Useful in pregnant women
      • 50% of the adult population has B19 antibodies (immune).
26
Q

Measles

  1. What type of virus is it?
  2. It has a high clinical pentrance - what does this mean?
  3. It is highly infectious - what does this mean?
  4. What is diagnosis?
A
  1. Morbillivarus, RNA, enveloped
  2. Nearly all infected individuals become unwell and develop disease. (High clinical penetrance) - in contrast to most other viral infections, usually a significant proportion of individuals have subclinical infection
  3. nearly all susceptible children contract the disease on exposure - After infection, there is complete resistance to re-infection, which is lifelong.
  4. IgM (serum or saliva), PCR resp or urine
27
Q

Measles

  1. What is the incubation period?
  2. What are some respiratory symptoms?
  3. What are other important symptoms?
A
  1. 10 days
  2. Conjunctivitis (98% have), runny nose, fever and cough
  3. Koplik’s spots (pathomneumonic) - little white spots within the mouth, and rash.
28
Q

Measles Complications

Outline some of the main complications associated with measles

A
  • opportunistic bacterial superinfections,
    • otitis media and pneumonia,
    • as a result of virus damage to respiratory surfaces
  • a primary measles virus pneumonia (giant cell pneumonia)
    • Seen in immunocompromised patients
  • encephalitis (1 in 1000 cases)
  • subacute sclerosing panencephalitis (SSPE).
    • very rare
    • develops 1-10 years after apparent recovery from acute infection.
29
Q

Measles in Malnourished child in 3rd world

What are these children more likely to suffer from?

A
  • Severe disease
  • pneumonia
  • Diarrhoea
  • Death

striking contrast developed and developing world

30
Q

Outline the measles vaccine

A
  • live attenuated vaccine
    • available since 1963.
    • effective, safe and long-lasting
    • Part of MMR
    • Before a vaccine became available, measles killed 7-8 million children each year worldwide.
    • By 1996, this was reduced to 1 million
    • Should be emiliminated from the world in the next few years
31
Q

Rubella

  1. Describe the virus
  2. Who is the main impact on?
  3. How is it spread?
  4. How contagious is it?
  5. Outline the vaccine?
A
  1. single-stranded RNA virus
  2. Multisystem infection tends to be mild - main impact is on the fetus- congital rubella syndrome (multi system severe or deafness alone)
  3. droplet transmission
  4. less contagious than measles, but more contagious than than mumps.
  5. Vaccine- live attenuated. Part of MMR
32
Q

Rubella

  1. What is the incubation period?
  2. What symptoms does it give rise to?
A
  1. 12-21 days
  2. •mild disease, with fever, malaise
  • irregular maculopapular rash lasting 3 days.
  • enlarged lymph nodes behind the ear
  • arthralgia
  • infection is commonly subclinical.
33
Q

Arthropod skin infections (infestations)

  1. Outline these
  2. Give examples
  3. What are the clinical implications of the above?
A
  1. live on blood/ tissue fluids from humans - Some human specific. Feeding processes and release of saliva - skin irritation & Immunological response
  2. lice and scabies mites
  3. skin conditions arise from:
  • the activity of the arthropods themselves
  • Their production of excreta
  • the oozing of blood and tissue fluids from the feeding sites
  • the host’s inflammatory reaction.
34
Q

Myiasis

  1. What is the causal agent?
  2. What is the mechanism of infection?
  3. What are the clinical implications?
  4. What is treatment?
A
  1. Diptera flies in tropics
  2. –larvae develop in skin

–Female flies lay eggs or larvae directly onto the skin,

–Larvae feed and grow in the skin of a mammal, just below the surface, escaping before or after pupation to release adult form.

  1. painful reactions, and large lesions may develop.
  2. treatment involves removal of the larvae, alleviation of symptoms and prevention of secondary infection.
35
Q

Lice

  1. What are the three types of Pedicuosis?
  2. What is the treatment?
A

1.

–head lice = Pediculus humanus capitis

–body lice = Pediculus humanus corporis

–pubic lice = Phthirus pubis

  • (eggs are called ‘nits)*
  • 2.*

–use of insecticidal creams, lotions, shampoos and powders e.g. containing malathion.

–Surface acting agents - interfere with lice respiraton

36
Q

Mites

  1. What is the method of infestation of scabies?
  2. What are the clinical implications?
  3. What is treatment with?
A
  1. Sarcoptes scabiei Mite lives its whole life in burrows within the skin - The female lays eggs into these burrows, characteristic rash with itching, and secondary infections may follow scratching.
  2. Wrists and hands - Can affect whole body

– Very heavy infections may develop in immunocompromised individuals or in people who are unable to care adequately for themselves.

‘Norwegian scabies’ - extensive thickening and crusting of the skin.

  1. Malathion or benzyl benzoate

(Within little burrows in skin – faecal material can be – this is what the main inflammatory response is to, not the live mite.

Seen in homeless people who havent good access to hygiene, can end up with overwhelming) complications

37
Q

Case

  • You are a GP:
  • A 4 year old child with a history of eczema, presents with a severe blistering rash.
  • What microbiological investigations should we do?
A

Think of HSV because the child has eczema

Normal to use aciclovir

If very severe may need to be admitted to hospital

  • PCR on a swab of a ruptured lesion.
    • The fluid will have loads of virus in it. Black and white answer from the lab.

Pathology (35 decks)

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