SPR L1 Childhood Exanthems and Selected Skin Manifestations Flashcards
What is an Exathem?
A skin rash
What do the following agents cause?
- HSV
- Varicella
- Enterovirus
- Erythrovirus B19
- Measles Virus
- Rubella Virus
- Vesicular Lesions
- Chickenpox shingles
- Rashes
- Rash
- Measles
- Rubella
Childhood exanthems - what are the key agents?
HSV
Varicella
Enterovirus
Erythrovirus B19
Measles Virus
Rubella Virus
+ arthropod infestations (lice, mites, myiasis
Learning Outcomes
- 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.
Which agents cause vesicular skin lesions?
HSV and Varicella
Which agents cause exanthems?
enterovirus rashes, erythrovirus B19, measles, rubella
What are the subfamilies of Herpes?
- Alpha-herpesvirus
- HSV-1
- HSV-2
- VZV
- Beta-herpesvirus
- CMV
- Gamma-herpesvirus
- EBV
Herpes simplex virus (HSV)
- When is it acquired?
- Describe it’s size
- What are the two types?
- How are they distinguishable?
- What is the basic lesion seen?
- How is the infection transmitted?
- Mostly in early childhood
- medium-sized (120 nm), double-stranded DNA
- HSV1 (oral and genital infections) and HSV2 (genital infections)
- distinguishable antigenically.
- Intraepithelial vesicle
- from the saliva or cold sores of other individuals.
HSV infection
- Where does the virus replicate?
- Outline what happens during the primary infection (e.g. gingivostomatitis)?
- Where does the latent virus remain?
- What happens when the lesion resolves?
- in oral mucosa/skin - virus rich VESICLES
- virus enters sensory nerve endings
–transported to the dorsal root (trigeminal) ganglion
–latent infection in sensory neurones
- In the sensory ganglion.
- antibody / CMI responses develop.
latent virus remains in the sensory ganglion for life,
& can reactivate (2ndry infection) to cause cold sores.
HSV
Where can a primary and secondary infection occur in , give examples?
- 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)
Give examples of some complications associated with HSV
- 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
What can HSV reactivation be provoked by?
- febrile illnesses
- (e.g. common cold, pneumonia)
- direct sunlight (UV)
- stress
- trauma
- ?menstruation
- immunocompromise.
What is a sensory prodrome?
A sensory prodrome in the affected area (feeling pins and needles, pain, burning, and itching) precedes the appearance of the coldsore
HSV Treatment
- What is the main treatment?
- How does it act, what is a benefit?
- What are the alternatives?
- When must the main drug be given IV?
- Aciclovir, Oral or IV, or supression (continuous low dose)
- acts specifically in virus-infected cells - Because Viral Thymidine kinase activates the drug, so it is well tolerated
- valaciclovir (valine ester of aciclovir), famciclovir (modified aciclovir with a longer half life)
- for encephalitis or disseminated HSV infection
& in immunocompromised individuals..
HSV Diagnosis
How can HSV be diagnosed?
- 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
Varicella Zoster Virus
- What does the primary infection give rise to?
- What is the incubation period?
- What does reactivation give?
- When can it occur?
- How can it be age related?
- Chickenpox, very infectious. (94% adults in NI are immune)
- 14-16 days
- Zoster (shingles).
- Years/decades after
- loss of cell mediated immunity to varicella with age
Describe some lesions that may appear with Varicella
- Macule - flat
- Papule - raised edge you can feel
- Vesicle - inside of papule is fluid filled
- Pustule - material inside is cloudy
What are the Key Complications of Varicella?
- Pneumonia - primary varicella, Secondary bacterial pneumonia can also occur
- CNS Involvement - Lymphocytic meningitis, Encephalitis
- Primary infection during pregnancy
Zoster - Reactivation
- What are the main characteristics?
- What is a common complication in elderly patients?
- What are the factors predisposing to zoster?
1.
- Dermatome distribution
- somatic
- trigeminal
- Thoracic dermatomes most common
- Paresthesia and pain
- erythematous rash -> vesicles
- fever and malaise.
- erythematous rash -> vesicles
- Post zoster neuralgia (pain)
3.
- Increasing age.
- Immunocompromise
- Trauma or tumors affecting the brain or spinal cord
Diagnosis of Chickenpox and Zoster
What are the main methods of diagnosis?
- 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
VZV Treatment
- What is the treatment?
- Outline the vaccine
- Similar to HSV but Acyclovir needs used at higher dose than for HSV
- live attenuated vaccine
licensed in a number of countries
universal childhood immunization in USA since 1995
Not in UK so far
Enteroviruses (picornavirus family)
- Name two viruses this family includes
- What do they give rise to?
- Who does it affect?
- What else can these viruses be responsible for?
- What is Hand Foot and Mouth usually caused by?
- coxsackie and echoviruses
- a variety of exanthems (Maculopapular rashes in summer)
- young children mostly
- illnesses affecting the CNS, URTI and occasionally heart muscle
- Coxsackie A16
Erythrovirus B19
- What type of virus is this?
- What does it cause?
- How is it spread?
- Parovirus - very small (22 nm diameter) ss DNA
- Febrile illness in children & maculopapular rash on face (‘slapped cheek syndrome’), AKA ‘erythema infectiosum’ or ‘fifth disease‘ - Symptomless infection is common
- respiratory droplets
B19 - Complications
- Where does it B19 grow?
- What does this lead to?
- What can the virus cause when it affects adults?
- What can it cause when an in utero infection?
- hemopoietic cells in the bone marrow
- 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)
- arthralgia
- Hydrops fetalis
B19 - Diagnosis
How is it tested for?
- erythrovirus B19-specific IgM.
- PCR on blood
- IgG immunity testing
- Useful in pregnant women
- 50% of the adult population has B19 antibodies (immune).
- Useful in pregnant women
Measles
- What type of virus is it?
- It has a high clinical pentrance - what does this mean?
- It is highly infectious - what does this mean?
- What is diagnosis?
- Morbillivarus, RNA, enveloped
- 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
- nearly all susceptible children contract the disease on exposure - After infection, there is complete resistance to re-infection, which is lifelong.
- IgM (serum or saliva), PCR resp or urine
Measles
- What is the incubation period?
- What are some respiratory symptoms?
- What are other important symptoms?
- 10 days
- Conjunctivitis (98% have), runny nose, fever and cough
- Koplik’s spots (pathomneumonic) - little white spots within the mouth, and rash.
Measles Complications
Outline some of the main complications associated with measles
- 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.
Measles in Malnourished child in 3rd world
What are these children more likely to suffer from?
- Severe disease
- pneumonia
- Diarrhoea
- Death
striking contrast developed and developing world
Outline the measles vaccine
- 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
Rubella
- Describe the virus
- Who is the main impact on?
- How is it spread?
- How contagious is it?
- Outline the vaccine?
- single-stranded RNA virus
- Multisystem infection tends to be mild - main impact is on the fetus- congital rubella syndrome (multi system severe or deafness alone)
- droplet transmission
- less contagious than measles, but more contagious than than mumps.
- Vaccine- live attenuated. Part of MMR
Rubella
- What is the incubation period?
- What symptoms does it give rise to?
- 12-21 days
- •mild disease, with fever, malaise
- irregular maculopapular rash lasting 3 days.
- enlarged lymph nodes behind the ear
- arthralgia
- infection is commonly subclinical.
Arthropod skin infections (infestations)
- Outline these
- Give examples
- What are the clinical implications of the above?
- live on blood/ tissue fluids from humans - Some human specific. Feeding processes and release of saliva - skin irritation & Immunological response
- lice and scabies mites
- 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.
Myiasis
- What is the causal agent?
- What is the mechanism of infection?
- What are the clinical implications?
- What is treatment?
- Diptera flies in tropics
- –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.
- painful reactions, and large lesions may develop.
- treatment involves removal of the larvae, alleviation of symptoms and prevention of secondary infection.
Lice
- What are the three types of Pedicuosis?
- What is the treatment?
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
Mites
- What is the method of infestation of scabies?
- What are the clinical implications?
- What is treatment with?
- 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.
- 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.
- 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
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?
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.
