Viral infection of the skin

Dr J Purcell

MBBS1

Friday 12th August 2011

Learning objectives

• To have an overview of the virological diversity of skin infections

• To be able to distinguish between localised viral skin infections and those with skin manifestations as a result of a systemic infection

• To know the aetiology, presentation, diagnosis, complications & treatment of common viral infections affecting the skin

Basic skin terminology

Flat

lesions

Raised

lesions

Fluid

filled

lesions

Smallest Macule Papule Vesicle

patch Nodule Blister

Largest plaque Bulla

viral rashes are frequently described as ‘maculopapular’.......................

Localised viral skin conditions

• Not a systemic illness

– signs confined to site of infection

• exceptionally may have associated Sx, eg primary

genital herpes infection

• Herpes simplex

– cold sores and genital herpes

• Herpes zoster

• Molluscum contagiosum

• Viral warts

• Orf

Herpes simplex (cold sores and

genital herpes)• HSV1 & HSV2

– ds DNA viruses

• Spread via saliva and genital secretions – usually infects mucous membranes but can infect minor skin

abrasions

• Basic lesion is intraepithelial vesicle

• Primary infection: herpetic gingivitis or genital herpes

• Latency in sensory ganglion

• Recurrences usually milder, closer grouping of smaller vesicles

• ComplicationsEye (dendritic ulcer), throat, eczema herpeticum, encephalitis,

meningitis (HSV2)

• Treatment: aciclovir, valaciclovir

Herpes simplex

Molluscum contagiosum

• Pox virus

• Common condition often seen in children

• Transmitted by contact

• Umbilicated flesh coloured papules – Koebnerisation seen

• May persist for months or years

• May be seen in association with immunosuppression– HIV

• Treatment: may not be necessary, minor surgery, cryotherapy, wart paints

Molluscum contagiosum

Viral warts

• Human papillomavirus (>120 types) dsDNA

• Spread by direct contact or autoinoculation into minor abrasions

• Various different types– Common, plantar, mosaic, plane, periungal, filiform,

oral, genital

• Genital warts usually types 6 and 11

• HPV 16,18, 31, 33, 35 associated with cervical cancer

from www.ncbi.nlm.nih.gov/books

Viral warts

treatment of warts

• In children, even without treatment, 50% of warts disappear within 6 months; 90% are gone in 2 years.

• More persistent in adults and imunosuppressed

• Treatment-chemical, cryotherapy

• Vaccination available against 16,18 and 6,11,16,18

• Many traditional remedies

Orf• Parapox virus

• ‘Contagious pustular

dermatitis’ in sheep

• Zoonosis

– sheep and goats

• Human lesions from

direct inoculation

– occurs in sheep farmers,

vets

• Incubation 5-6 days then

firm red, reddish- blue

lump which forms blister

or pustule

• Usually solitary, self

limiting

Common childhood viral infections

causing exanthems

• Measles

• Rubella

• Chicken pox

• Fifth disease

– ‘slapped cheek’, parvovirus B19

• Roseola

– ‘Exanthem subitum’, HHV 6/7

• Infectious mononucleosis/glandular fever

• Echovirus and adenovirus infections

Viral exanthems

•A rash with systemic symptoms, due to systemic

spread of virus

•The rash may or may not represent a site of virus

repication

•The rash may be immune mediated

Measles

• Paramxyovirus (enveloped ssRNA)

• Highly infectious, 90-100% susceptible contacts will show symptomatic disease

• Devastating disease in malnourished populations– estimated 1 million deaths per year worldwide in this setting

• Seasonality seen- dry season sees most cases

• Relies on cell mediated immunity for control

• Produces temporary defects in immunity for up to 1 month after illness

Measles timeline

day 0

invasion of local lymphatics

spread to lymphoid tissue throughout the body

enters blood next, then arrives at epithelial sites

eg respiratory tract, gastrointestinal,

skin

day 7-14 onset of symptoms

1. Prodrome

acute respiratory syndrome

conjunctivitis, fever

2. Kopliks spots 1 day prior

to rash, last for <48 hours

3. Skin rash, 3-4 days later

starts from face/head and

spreads to rest of body

Contagious

1 day prior to symptoms, until

approx day 4 of rash

Measles

Measles

• Complications– Diarrhoea exacerbating underlying

malnutrition

– Otitis media

– Pneumonia (either primary viral or secondary bacterial). The most common cause of death.

– Haemorrhagic rash

– Corneal disease leading to blindness esp if Vit A deficient- xerophthmia

– SSPE-v. rare

• Usually a clinical diagnosis

• IgM serology from blood or saliva for lab confirmation

• Prevention: – Vaccination. Live attenuated vaccine,

either single/MMR

Rubella (German measles)

• Togavirus, often asymptomatic

• Mild illness short lived illness

• Significance in pregnant women

• Incubation period 14-21 days, spread via nose/throat secretions

• Contagious 5 days pre symptoms to 3 days into symptoms

• Slight fever, sore throat, coryza, malaise

• Rash starts face, spreads to neck, trunk, extremities, may/may not be itchy

• Usually tender swollen occipital lymph nodes

• Sometimes arthralgia and arthritis

Rubella

post auricular lymphadenopathy

• Complications: Congenital Rubella Syndrome in 50% affected 1st trimester

• Prevention:– vaccination, live

attenuated vaccine (MMR)

Chicken pox- varicella zoster

virus• Largely childhood disease, more severe in adults

• Incubation period 10-21 days. Infectious 2 days pre illness - rash scabs

• Airborne spread or direct contact with vesicles

• May be prodrome, then itchy cropping rash of red papules starts on stomach, back and face then spreads, becomes vesicular, pustular then scabs

• Complications– Secondary bacterial infection, Viral pneumonia, disseminated

infection, CNS involvement, haemorrhagic lesions, scarring

– Congenital infection

• Diagnosis is clinical

• Consider aciclovir in >12y and immunocompromised. Passive immunisation with ZIG may modify disease

Chicken pox

Herpes zoster

• VZV remains latent in dorsal root ganglion

• Recurrence gives shingles in dermatome

– can be seen in children congenitally infected

in 2nd or 3rd trimester

• Usually pain, fever, headache precedes

blistering rash

• Complications

– post herpetic neuralgia

– ophthalmic shingles causing keratitis

• Diagnosis: clinical, IF, PCR of vesicle fluid

• Treatment: aciclovir as soon as possible

Herpes zoster

Other childhood exanthems

• Erythema infectiousum (fifth

disease/slapped cheek disease)

– Parvovirus B19

• Roseola (exanthem subitum)

– HHV6, HHV7

• Infectious mononucleosis (Glandular

fever)

– EBV

Other viral syndromes affecting

skin

• Hand, foot and mouth disease

– Coxsackie virus

• Smallpox, Cowpox, Monkey pox

• Arboviruses

– Chikungunya fever, Dengue and Dengue

haemorrhagic fever

• HIV

• Viral Haemorrhagic Fevers

HIV related viral disease

• Acute morbilliform rash due to HIV

• Viral infections– HSV, VZV, Molluscum,

HPV, oral hairy leukoplakia

• Malignancies – Eg Kaposi’s sarcoma

(coinfection with HHV8)

Suggested reading / viewing• Mims Medical Microbiology Goering, Dockrell et al

• 4th edn

– p368-385

• Medical Microbiology Greenwood et al

• 17th edn

– P662(general, v short!); P415-439 (herpesviruses); P440-445 (poxviruses); P446-453 (papillomaviruses); P501-502 (measles); P524-526 (rubella)

Review pictures in:

• An Atlas of African Dermatology by B Leppard

• Dermatology of Black Skin by A Basset, B Liautaud, B

Ndiaye

• http://web.squ.edu.om/med-

Lib/MED_CD/E_CDs/health%20development/html/client

s/skin/html/skin_06.htm#7