Viral Skin Infections Flashcards
What is herpes-simplex?
Herpes simplex = common viral infection that presents with localised blistering
=> commonly known as cold sores or fever blisters, as recurrences are triggered by a febrile illness i.e. cold
What causes herpes-simplex?
Herpes simplex is caused by:
Type 1 HSV is mainly associated with oral and facial infections
Type 2 HSV is mainly associated with genital and rectal infections
After primary infection, HSV is latent in spinal dorsal root nerves that supply sensation to the skin.
During a recurrence, the virus follows the nerves onto the skin or mucous membranes, where it multiplies, causing the clinical lesion.
Who is at risk of herpes-simplex?
Primary attacks of Type 1 HSV infections:
=> mainly in infants and young children
Type 2 HSV infections:
=> mainly transmitted sexually
HSV is transmitted by direct or indirect contact with active herpes simplex (infectious for 7–12 days)
Asymptomatic shedding of the virus in saliva or genital secretions can also lead to transmission of HSV - rare
Minor injury helps inoculate HSV into the skin. For example:
Primary infection can be mild or subclinical
Symptomatic primary infection more severe than recurrences.
*Type 2 HSV is more often symptomatic than Type 1 HSV
What is the clinical presentation of primary herpes-simplex?
- Primary Type 1 HSV most often presents as gingivostomatitis, in children 1-5 years
Primary type 1 Symptoms: => fever, => restlessness => excessive dribbling => painful drinking and eating => foul breath i => swollen, red gums that bleed easily => whitish vesicles evolve to yellowish ulcers on the tongue, throat, palate and inside the cheeks => Local lymph glands are enlarged and tender.
Recovery within 2 weeks
- Primary Type 2 symptoms:
=> genital herpes after sexual activity.
=> painful vesicles, ulcers, redness and swelling lasting for 2 to 3 weeks
=> if untreated accompanied by fever + tender inguinal lymphadenopathy
Males: glans, foreskin and shaft of the penis
Females: vulva and in the vagina. Painful, difficult to pass urine.
What is the clinical presentation of recurrent herpes-simplex?
May be no further clinical manifestations throughout life.
Immunodeficient => type 2 recurrent infections are common
Recurrences can be triggered by:
=> Minor trauma, surgery or procedures to the affected area
=> Upper respiratory tract infections
=> Sun exposure
=> Hormonal factors esp in women
=> Emotional stress
Smaller, group vesicles in recurrent herpes.
Itching or burning is followed an hour or two later by an irregular cluster of small umbilicated vesicles on a red base
Heal in 7–10 days without scarring - may be accompanied by fever, pain and have enlarged local lymph nodes
How is herpes diagnosed?
If there is clinical doubt, HSV can be confirmed by culture or PCR of a viral swab taken from fresh vesicles.
HSV serology +ve in most so not useful in diagnosis
What are the complications of herpes simplex?
Eye infection: conjunctivitis and superficial ulceration of the cornea
Throat infection: very painful and interfere with swallowing
Eczema herpeticum: hx of atopic dermatitis => severe and widespread infection (numerous blisters erupt on the face associated with swollen lymph glands and fever)
Erythema multiforme (herpes most common cause of Erythema multiforme) : rare in herpes
Nervous system: cranial/facial nerve palsies; neuralgic pain (rare)
Widespread infection: disseminated infection and/or persistent ulceration
How is herpes simplex treated?
Mild, uncomplicated eruptions of herpes simplex = no treatment
Blisters may be covered i.e. with a hydrocolloid patch
Antiviral drugs for severe herpes simplex
i.e. Aciclovir
How can herpes simplex be prevented?
Limit sun exposure by wearing a high factor sunscreen - triggers facial herpes
Antiviral drugs shorten and prevent attacks frequent attacks.
What is chicken pox?
Highly contagious viral infection that causes an acute fever and blistered rash.
Chickenpox affects anyone but most commonly in children <10 years of age.
Once you have had chickenpox, it is unlikely to get it again = lifelong immunity
What causes chicken pox?
Varicella-zoster virus (herpesviridae family)
*sometimes called herpesvirus type 3
Chickenpox = highly contagious and spread in airborne respiratory droplets from an infected person’s coughing or sneezing or through direct contact with the fluid from the open sores
=> enters through the mucosa of upper respiratory tract
A person who is not immune to the virus has a 70–80% chance of being infected with the virus if exposed in the early stages of the disease.
What are the signs and symptoms of chicken pox?
=> Rapid progression of macules to papules to vesicles to pustules within hours
=> on the stomach, back and face then spreads to other parts of the body
=> more severe in older children / debilitating in adults - experience prodromal symptoms i.e. fever, malaise, headache, loss of appetite, abdo pain upto 48hrs before breaking out in the rash
*pustules crust & clear up within one to three weeks, without scarring
How is chicken pox diagnosed?
Clinical diagnosis mostly
Laboratory tests can confirm the diagnosis:
=> PCR detects the varicella virus in vesicular fluid from skin lesions = most accurate method for diagnosis
=> Serology in pregnant women
What are the complications of chicken pox?
- Bacterial superinfection of scratched lesions => lead to abscess, cellulitis, necrotising fasciitis and gangrene
- Viral pneumonia - more common in adults + smokers
- Disseminated primary varicella infection = high morbidity
- CNS - commonly presents with acute truncal cerebellar ataxia
=> i.e. Reye syndrome,
=> Guillain-Barré syndrome
=> encephalitis - Thrombocytopenia and purpura
- Exposure to varicella virus in pregnancy = viral pneumonia, premature labour & delivery and rarely maternal death
- Congenital varicella syndrome (TORCH) => spontaneous abortion, fetal chorioretinitis, cataracts, limb atrophy, cerebral cortical atrophy and microcephaly, cutaneous scars, and neurological disability.
Mortality in newborns infected with varicella is up to 30%.
How do you manage / prevent chickenpox?
Healthy patients = no treatment + lifelong immunity from infection
Aciclovir in patients >16years
High dose Aciclovir + zoster-immune globulin in immunocompromised
Prophylaxis zoster-immune globulins in susceptible pregnant women
=> Aciclovir if chickenpox during pregnancy
Effective live attenuated varicella vaccine licensed in US but named patient basis in UK + susceptible healthcare workers
Is there a vaccination for chicken pox?
Yes
Effective live attenuated varicella vaccine licensed in US but named patient basis in UK only + susceptible healthcare workers
What is shingles?
Shingles is the re-activation of the herpes zoster virus most common in elderly but can affect anyone.
After chicken pox infection, the virus lays dormant in dorsal root and cranial nerve ganglia.
What is the clinical presentation for shingles?
Prodromoal phase : itch, tingling or pain
Painful, unilateral, blistering eruption in a dermatomal distribution
Blisters appear in crops + may become purulent before crusting
Rash lasts 2-4 weeks
More severe in elderly + immunocompromised with involvement of >1 dermatome
How do you manage shingles?
Analgesia + antibiotic if superimposed bacterial infection
Oral antiviral therapy within 72h of onset of the rash + continued for 7-10d
=> reduce pain (inc. post-herpetic pain)
=> reduce severity of disease
=> reduce viral shedding
Live attenuated shingles vaccine recommended for all >70yrs in UK
=> reduces mortality
What is the most common complication of shingles?
Post-herpetic neuralgia
=> occurrence related to age (more likely in elderly) and intensity of original shingles rash
Ocular disease if ophthalmic division of trigeminal nerve involved
Facial (CNVII) nerve involved = facial palsy
Motor neuropathy (rare)
What are viral warts?
Viral wart = very common benign lesion caused by infection with human papillomavirus (HPV).
Viral warts classified by site:
=> cutaneous
=> mucosal
HPV affects keratinocytes in the skin and epithelial cells in mucosa.
A cutaneous wart is also called a verruca or papilloma, and warty-looking lesions of any cause described as verrucous or papillomatous.
Who is at risk of cutaneous viral warts?
School-aged children / may occur at any age
People with dermatitis, due to a defective skin barrier
Immunosuppression
What causes cutaneous viral warts?
Which part of the skin is infected?
How is it spread?
Human papillomavirus (HPV) => infection in the basal layer of the epidermis, causing proliferation of the keratinocytes and hyperkeratosis => the wart.
The most common HPV types infecting the skin are types 1, 2, 3, 4, 10, 27, 29, and 57.
HPV is spread by
=> direct skin-to-skin contact
=> autoinoculation : if a wart is scratched, the viral particles may be spread to another area of skin.
What are the 4 main types of common warts?
Common warts
Plantar warts (verrucae)
Plane warts
Anogenital warts
What are the clinical features of common warts?
Cauliflower like papules with rough papillomatous and hyperkeratotic surface
Commonly on knees, backs of fingers, toes and around nails
Solitary or multiple
Warts on face = elongated (filiform)
Most common in children / young adults
Often resolve spontaneously (some are stubborn)
Complications: SCC
What are the clinical features of plantar warts (verrucae)?
Warty papillomatous surface but flattened due to pressure
Skin-coloured or brown-ish lesions
Tender if warts on pressure points or around nail folds
Infectious
HPV 1 & 2
What are the clinical features of plane warts?
Multiple, smaller, flatter papules than common warts
Flesh-coloured or lightly pigmented
Found on face or backs of hands
Caused by HPV types 3 & 10
What are the clinical features of anogenital warts (STI)?
Painless, benign superficial epithelial lesion caused by HPV 6 & 11
Warts appear 3-6months after infection
What are the complications of viral warts?
=> Contagious
=> Significant psychosocial/sexual effects + impact on quality of life
=> Pain due to plantar warts
=> Risk of cutaneous SCC
=> Anogenital warts can enlarge and multiply during pregnancy + may interfere with delivery
=> HPV can be transmitted to baby during delivery
How is cutaneous viral wart diagnosed?
Clinical diagnosis
Dermascopy
Skin biopsy if SCC not excluded
What are the differentials for viral warts?
Cutaneous viral warts
=> seborrhoeic keratosis
=> Squamous cell carcinoma
=> Plantar corn & callous
Genital warts => Pearly papules => Sebaceous glands on labia => Vestibular papillae => Seborrhoeic keratoses => Anogenital squamous cell carcinoma
How are viral warts treated?
No definitive cure and warts can persist for months / years
Salicylic acid (keratolytic agent)
Cryotherapy
Curettege & cautery
Laser ablation therapy
Avoid excision in plantar warts => After abrading it, try salicylic acid under an occlusive plaster
HPV vaccine at young age for genital warts
What is molluscum contangiosum?
Common viral skin infection of childhood
Causes localised clusters of epidermal papules called mollusca
Who is at risk of molluscum contangiosum?
=> Children <10 year
=> More prevalent in warm climates and in overcrowded environments.
=> More persistent in children who also have eczema due to defective skin barrier
What causes molluscum contagiosum?
How is it spread?
Caused by a poxvirus
=> Direct skin-to-skin contact
=> Indirect contact via shared towels or other items
=> Auto-inoculation into another site by scratching or shaving
=> Sexual transmission in adults.
Incubation period 2 weeks to 6 months.
What are the clinical features of molluscum contagiosum?
Clusters of small round translucent firm papules
White, pink or brown
With a small central pit (umbilicated)
Papule contains soft white keratinous matter which can be squeezed out
In warm moist places i.e. the armpit, behind the knees, groin or genital areas
=> not on palms or soles
Molluscum contagiosum frequently induces dermatitis around them and affected skin becomes pink, dry and itchy.
As the papules resolve, they may become inflamed, crusted or scabby for a week or two.
What is the treatment for molluscum contagiosum?
No treatment needed - self-resolving
Cryotherapy / curettage in older childer
