6- Dermatology (Skin infections: Viral and infestations) Flashcards
chicken pox background
- Highly infectious disease
- Mostly mild to moderate and self-limiting
o Milder in younger children
o Infection severe in pregnancy- high risk of pneumonia and risk to fetus - Can be dangerous for immunocompromised or older adults
- Endemic in most countries
shingles
Reactivation of dormant virus after bout of chickenpox leads to herpes zoster (Shingles)
o Like chickenpox but confided to just one dermatome
causes of chicken pox
Varicella-Zoster virus (DNA)
Risk factors for chicken pox
- Immunocompromised missed e.g. HIV, children
- Older age
- Steroid use
- Malignancy
transmission of chicken pox
- Transmission- virus enters through upper respiratory tract
- Viraemia occurs 4-6 days later
- Skin lesions last 10-14 days
chicken pox infectivity
Infectivity is from a few days before onset of lesions until the crust falls off
Presentation of chicken pox
- Prodrome- pyrexia, headache and malaise
- Crops of vesicles , mostly on head , neck and trunk, sparse on limbs (new lesions stop after 4 days)
- Papules -> vesicles -> pustules -> crust
- When crust falls off they may leave a mark which will be present for a few weeks (higher risk of scarring in older children )
- Redness around lesion could be bacterial superinfection
management of chickenpox
- Simple advice: fluid intake, minimising scratching, avoid contact with pregnant women and neonates
- Symptomatic treatment – paracetamol (analgeisa and antipyretic), give antihistamine and emollients to help with pruritus
- Do not give NSAIDS (risk of necrotising soft tissue infections)!!!
- Acyclovir not recommended in children
- Encephalitis – admission to hospital
Advice to give parents whos children have chicken pox
- Incubation period of 14-16 days
- Keep child home from school for 5 days
- Infective 24h before and until rash crusts
herpes zoster
shingles
shingles background
- Viral infections, almost always affect the skin of a single dermatome
- Occurs wh›en the host is immunosuppressed- VZV (varicella zoster virus) reactivates and travels through peripheral nerve to skin of single dermatome
pathophysiology of shingles
Virus travels through a cutaneous nerve and remains dormant in dorsal root ganglion after chickenpox
presentation of shingles
- Rash along nerve root
- Painful blisters that scab over
- Itchy, tingly, burning pain
shingles management
Severe e.g. **Hutchinson’s sign **or visual symptoms or serious complication, immunocompromised
- Admit to hospital
- May require aciclovir
Mild
- Analgesia
Prevention of shingles
zoster vaccine (>70-79)
Molluscum contagiosum
Background
- Viral skin infection caused by molluscum contagiosum virus, which is a type of poxvirus
- Spread through direct contact or by sharing towels or bedsheets
presentation of molluscum contagiosum
Presentation
- Small flesh colours papules (raised individual bumps on the skin) that characteristically have a central dimple
- Appear in crops of multiple lesions in a local area
manageemnt of molluscum
Papules resolve by themselves, although this can take up to 18 months.
- Can continue all their normal activities
- Should avoid towel sharing
- Bacterial superinfection may require topical fusidic acid or oral flucloxacillin
Advice
Scratching or picking should be avoided as it can lead to spreading, scarring and infection
management of molluscum if immunocompromised or very extensive lesions
If immunocompromised or very extensive lesions or lesions in genital or eyelids:
- Topical potassium hydroxide, benzoyl peroxide, podophyllotoxin, imiquimod, tretinoin
- Surgical removal and cryotherapy – can lead to scarring
Pityriasis rosea background
Background
- acute, self-limiting rash which tends to affect young adults.
Causes/ risk factors
- The aetiology is not fully understood but is thought that herpes hominis virus 7 (HHV-7) may play a role.
presentation of pityriasis rosea
- in the majority of patients there is no prodrome, but a minority may give a history of a recent viral infection
- herald patch (usually on trunk)
- followed by erythematous, oval, scaly patches which follow a characteristic distribution with the longitudinal diameters of the oval lesions running parallel to the line of Langer.
- This may produce a ‘fir-tree’ appearance
management of pityriaisis rosea
Self limiting- disappears in 6-12 weeks
differentiating guttate psoriasis and pityriasis rosea
Herpes simplex virus (HSV)
Background
- Worldwide herpes virus is estimated to infect 66% of the population; more low- and middle-income.
- Responsible for both cold sores (herpes labialis) and genital herpes
- Many people have no symptoms
- Transmitted by contact of herpetic lesions, saliva or skin containing HSV-1/2 virus
- Clinical manifestation depends on site of disease and whether primary or latent infection.
Pathophysiology of HSV
- After an initial infection, the virus becomes latent in the associated sensory nerve ganglia.
- Typically this is the trigeminal nerve ganglion with cold sores and the sacral nerve ganglia with genital herpes.
HSV-1
- Cold sores
- It is often contracted initially in childhood (before five years), remains dormant in the trigeminal nerve ganglion and reactivates as cold sores, particularly in times of stress.
- Can cause herpes in genitalia through oral sex
HSV-2
- Spreads by sexual contact and causes genital herpe
- Genital herpes caused by HSV-1 is usually contracted through oro-genital sex, where the virus spreads from a person with an oral infection to the person that develops a genital infection.
presentation of herpes simplex infection
- Incubation- 2 weeks
- Asymptomatic
- Initial presentation most severe
- Ulcers or blistering lesions affecting the genital area
- Neuropathic type pain (tingling, burning or shooting)
- Flu-like symptoms (e.g. Fatigue and headaches)
- Dysuria (painful urination)
- Inguinal lymphadenopathy
Symptoms can last for 3 weeks in primary infection
investigations for HSV
Investigations
- The diagnosis can be made clinically based on the history and examination findings.
- A viral PCR swab from a lesion can confirm the diagnosis and causative organism.
management of genital herpes (usually HSV2)
Antiviral: aciclovir
Additional measures
- Paracetamol
- Topical lidocaine 2% gel (instillagel)
- cleaning with warm salt water- key prevents secondary bacterial infection and dries up lesion
- topical vaseline
- additional oral fluid
- loose clothing
- avoid intercourse with symptoms
management of cold sore (HSV1)
- most resolve after 5 days without treatment
- topical antivirals applied prodromally can reduce duration by 12 to 18 hours
- if frequent, severe, and predictable triggers:
- consider oral prophylaxis: aciclovir 400mg, twice daily, for 5 to 7 days
Warts/ HPV Background
- Common benign lesion caused by infection with human papilloma virus
- Can be classified by site as being:
o Cutaneous e.g. Verrucas
o Mucosal e.g. Sexually acquired anogenital warts
Pathophysiology of warts
HPV
- Double stranded DNA virus
- Infection begins in the basal layer of the epidermis, cuasing proliferation of the keratinocytes (skin cells) and hyperkeratosis, and production of infectious virus particles- the wart
- Virus subtypes which infect the skin: 1,2,3,4,10,27,29,57
- Spread via direct skin to skin contact or autoinoculation
o E.g. if a wart is scratched or picked may devlop under the fingernail
- Incubation period as long twelve months
risk factors for warts
Risk factors
- School aged children
- People with immunosuppression
presentation of warts
- Cutaneous viral wards are hard due to their keratinous surface
- Tiny red or black dots can be visible in the wart are papillary capillaries
Management of warts
- Most warts resolve spontaneously especially in children
Indication for active treatment
- Immunosuppression
- Presence of complications
- Patient preference
treatments for warts
Topical treatment
- Paints or patches containing salicylic acid or podophyllin which remove the surface skin cells
- Applied once daily
Cryotherapy
- Liquid nitrogen – 3-4 months of regular freezing
Electrosurgery
- Curettage and cautery for large and resistant warts
Others
- Imiquimod cream
- Bleomycin injections
prevention of warts
- Wash hands regularly don’t touch warts
- Vaccines for anogenital warts
Differential diagnoses for a cutaneous viral wart can include:
- Seborrhoeic keratosis
- Squamous cell carcinoma
- Plantar corn and callus.
Head lice
Background
- Pediculus humanus capitis parasite
- Causes infestations of the scalp
- Spread by close contact with someone that has head lice
- Transmission is by head to head contact or by sharing equipment
- Lice cannot jump between hair
which parasite causes head lice
Pediculus humanus capitis parasite
presentation of head lice
- Itchy scalp
- Feel movement
- Often visible
risk factors of headlice
Risk factors
- School aged children
management of head lice
Management
- Dimeticone 4% lotion can be applied to the hair and left to dry. This is left on for 8 hours (i.e. overnight), then washed off. This process is repeated 7 days later to kill any head lice that have hatched since treatment.
- Special fine combs can be used to systematically comb the nits and lice out of the hair. They can be used for detection combing to check the success of treatment. NICE clinical knowledge summaries recommend The Bug Buster kit.
scbaies is causes by which parasitic mite
Sarcoptes scabiei
causes of scabies
- Spread through prolonged skin contact
- Typically affects children and young adults
- The scabies mite burrows into the skin, laying its eggs in the stratum corneum. The intense pruritus associated with scabies is due to a delayed-type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection.
Risk factors
for scabies
- Overcrowding
- Poverty
- Poor nutritional status
- Poor hygiene
- Sexual contact
- Immune suppression e.g HIV
- Most common in children
- Secondary to eczema and impetigo
Presentation of scabies
Presentation
- Severe pruritus worse at night
- Close contact with people with similar symptoms
- White lines – linear burrows indicative of mite burrowing
- Lesion may be
o Papules
o Vesicles
o Pustules
o Nodules
o erythematous
investigations for scabiee
Investigations
- Skin scrape
- Extraction of mite
- View under microscope
investigations for scabiee
Investigations
- Skin scrape
- Extraction of mite
- View under microscope
manageemnt of scabies (which treatment is first line vs second line)
Management (everyone in household treated)
- Permethrin 5% is first-line
- Malathion 0.5% is second-line
- Antihistamines
- Pruritus persists for up to 4-6 weeks post eradication
