Rash: Scabies Flashcards
What is scabies?
A highly infectious rash caused by the parasitic mite Sarcoptes scabiei.
How is scabies spread?
Direct skin to skin contact or via fomites (less common).
Cause of scabies?
An infestation of the skin by mite Sarcoptes scabiei resulting in a pruritic eruption
Appearance of rash in scabies?
Small, erythematous papule with haemorrhagic crusts on fingers, elbows, axillary folds, thighs, genitalia, feet.
What causes the rash in scabies?
From a local allergic reaction to the presence of the scabies mite, rather than being directly caused by the mite itself.
What are some key risk factors for scabies?
Living conditions: poverty and overcrowding are key risk factors.
This includes institutional care facilities, such as residential aged care homes, hospitals, and prisons.
Clinical features of scabies?
1) Intense, widespread pruritus
2) Linear burrows on the side of fingers, interdigital webs and flexor aspects of the wrist (face and scalp may be affected in infants)
3) 2ary features: excoriation, infection
1st line for management of scabies?
Permethrin 5%
2nd line for management of scabies?
Malathio 0.5%
How long can pruritus persist in scabies post eradication?
Up to 4-6 weeks
What causes the intense pruritus associated with scabies?
A delayed-type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection.
How does the BNF advise to apply the inseticide in scabies?
ALL areas, including the face and scalp.
Pay close attention to areas between fingers and toes, under nails, armpit area, creases of the skin such as at the wrist and elbow.
When should treatment be repeated in scabies?
7 days after
Where are scabies ‘burrows’ typically found?
These are small irregular tracks ~1cm in length, classically found in the webbed spaces between the fingers
What is crusted scabies?
A severe variant of scabies where an individual is infected with thousands or millions of mites (compared with 5-20 in a typical infection).
What is a key complication of scabies?
2ary bacterial infection of scabies rash (due to itching).
Which bacteria typically causes 2ary infection in scabies?
GAS (S.pyogenes) or S.aureus
What is measles caused by?
An infectious disease caused by a morbillivirus of the paramyxovirus family.
Appearance of measles rash?
Maculopapular rash lasts 6-8 days
What associated symptoms can there be in measles?
- prodrome: fever, coryza, cough, non-purulent conjunctivitis
- Koplik spots
How is measles spread?
Droplets
Incubation period of measles?
10-14 days
How long are you infective for with measles?
infective from prodrome until 4 days after rash starts
What are Koplik spots?
White spots (‘grain of salt’) on buccal mucosa.
These appear BEFORE the rash in measles.
Where does the measles rash typically start?
Behind the ears (and then spreads to the whole body)
Prevention of measles?
MMR vaccine at 18 months
Key investigation of measles?
IgM antibodies can be detected within a few days of rash onset
Managment of measles?
1) Notifiable disease –> inform public health
2) Mainly supportive
Who should admission be considered in in measles?
Immunosuppressed or pregnant women.
Management of a child who is not immunised against measles that comes into contact with measles?
Offer MMR vaccine (within 72 hours)
Why can the MMR vaccine be offered if a non immunised child comes into contact with measles?
As vaccine-induced measles antibody develops more rapidly than that following natural infection
What is the most common complication of measles?
Otitis media
What is the most common cause of death in measles?
Pneumonia
What are some complications of measles?
- Otitis media
- Pneumonia
- Encephalitis
- Subacute sclerosing panencephalitis
- Diarrhoea
- Myocarditis
What is impetigo?
A superficial bacterial infection affecting the skin.
What 2 organisms cause impetigo?
1) Staph. aureus
2) Strep. pyogenes (GAS)
Impetigo can be a 1ary infection or a complication of what?
Existing skin conditions e.g. eczema, scabies, or insect bites.
Spread of impetigo?
Direct contact with discharge from the scabs of an infected person.
Appearance of rash in impetigo?
- Erythematous macules (may progress to be vesicular/bullous).
- Lesions tend to occur on face, flexures and limbs not covered by clothing.
- ‘Golden’, crusted skin lesions typically found around the mouth.
1st line management of impetigo in those who are not systemically unwell or at a high risk of complications?
Hydrogen peroxide 1% cream
Other options –> topical Abx creams:
1) Topical fusidic acid
2) Topical mupirocin (if fusidic acid resistance)
What should be used in management of impetigo if MRSA is suspected?
Topical mupirocin
Management of extensive disease in impetigo?
1st line –> oral flucloxacillin
If penicillin allergic –> oral erythromycin
How long should children avoid school for in impetigo?
Children should be excluded from school until the lesions are crusted and healed or 48 hours after commencing antibiotic treatment.
What is nappy rash?
An irritant contact dermatitis that occurs in the nappy area.
2ary infection with Candida albicans or bacteria (Staphylococcal aureus or streptococcus) can occur.
Cause of nappy rash?
Candida albicans in skin creases.
Candida secondarily infects areas of irritant dermatitis that has been left untreated for more than 3 days.
Appearance of nappy rash?
Beefy red plaques, satellite papules, superficial pustules
Management of nappy rash?
1) frequent application of emollients
2) topical antifungal agent (e.g. nystatin, clotrimazole or ketoconazole
What causes chickenpox?
VZV
What is shingles?
Reactivation of the dormant VZV in the dorsal root ganglion.
How is chickenpox spread?
Via the respiratory route.
Can chickenpox be caught from someone with shingles?
Yes
Infectivity period in chickenpox?
From 4 days before rash, until 5 days after the rash first appeared
Apperance of rash in chickenpox?
Itchy rash starting on head/trunnk before spreading throughout body.
Macular –> papular –> vestcular.
Clinical features of chickenpox?
- fever initially
- itchy, rash starting on head/trunk before spreading
- systemic upset is usually mild: headache, acnorexia, URTI, fever, itching
Management of chickenpox?
Supportive:
- keep cool, trim nails
- calamine lotion
What should immunocompromised patients and newborns with peripartum exposure to chickenpox receive?
Varicella zoster immunoglobulin (VZIG)
If chickenpox develops –> consider IV aciclovir
What is a common complication of chickenpox?
2ary bacterial infection of the lesions
What increases the risk of 2ary bacterial infection of the lesions in chickenpox?
NSAIDs
How does 2ary bacterial infection of the chickenpox lesions typically present?
What can happen in severe cases?
Commonly manifests as a single infected lesion/small area of cellulitis.
In a small number of patients, invasive group A streptococcal soft tissue infections may occur resulting in necrotizing fasciitis.
What are some rarer complications of chickenpox?
- pneumonia
- encephalitis (cerebellar involvement may be seen)
- disseminated haemorrhagic chickenpox
- arthritis, nephritis and pancreatitis may very rarely be seen
When does eczema in children typically present?
<2y/o
But clears in around 50% of children by 5y/o, and 75% by 10y/o.
Features of eczema?
Itchy, erythematous rash.
Distribution of rash in eczema in infants vs young children vs older children?
Infants - face and trunk
Young children - extensor surfaces
Older children - flexor surfaces, creases of face and neck (typical distribution)
Management of eczema in children?
- Avoid irritants
- Simple emollients
- Topical steroids
- Wet wrapping
- Oral ciclosporin (severe cases)
How should emollients be applied in eczema?
Large quantities should be prescribed (e.g. 250g / week), roughly in a ratio of with topical steroids of 10:1.
If a topical steroid is also being used the emollient should be applied first followed by waiting at least 30 minutes before applying the topical steroid.
How should emollients vs topical steroids be applied?
The emollient should be applied first followed by waiting at least 30 minutes before applying the topical steroid
What is wet wrapping in eczema?
When large amounts of emollient (and sometimes topical steroids) applied under wet bandages
What is a key complication of eczema?
Eczema herpeticum
What is eczema herpeticum?
A complication of atopic eczema that occurs with infection of the HSV-1.
What is a key risk factor for eczema herpeticum?
Atopic eczema
Clinical features of eczema herpeticum?
- Areas of rapidly worsening, painful eczema
- Vesicular rash –> blisters may be filled with clear yellow fluid, thick purulent material or blood stained
- Punched-out erosions (circular, depressed, ulcerated lesions) usually 1-3mm that are uniform in appearance (monomorphic)
- Maybe: fever, lethargy, lymphadenopathy or distress
When should eczema herpeticum be referred for same day review?
In cases involving the skin around the eyes –> refer for same-day ophthalmology review
What investigation is indicated if herpetic keratitis is suspected?
Staining with fluorescein –> a stained dendritic ulcer is diagnostic
Management of eczema herpeticum?
Considered a dermatological emergency.
1) Oral aciclovir
2) Consider IV aciclovir
3) Consider Abx for 2ary bacterial infection
Management of ocular involvement in eczema herpeticum?
Ganciclovir ointment
What may be indicated in cases of postherpetic scarring that significantly affects vision?
A corneal transplant
What is the most common complication of eczema herpeticum?
2ary bacterial infection:
- Staphylococcus aureus might cause impetigo
- Streptococcal infection may cause cellulitis
What are some complications of eczema herpeticum?
1) 2ary bacterial infection
2) Scarring
3) Infection of the cornea leading to herpetic keratitis –> can lead to blindness
4) Organ failure and dissemination
mortality rate of eczema herpeticum?
6-10%
What are some management options in eczema?
1) Emollients
2) Topical corticosteroids
3) Topical calcineurin inhibitors e.g. tacrolimus
4) Antimicrobials (in cases of 2ary bacterial infection)
5) Phototherapy
6) Systemic Therapies e.g. ciclosporin
7) Biologic Therapy e.g. dupilumab
8) Management of Itch
Role of emollients in eczema?
They provide symptomatic relief by hydrating the skin, reducing transepidermal water loss and restoring the skin barrier function.
When are topical steroids indicated in eczema?
In acute flares and moderate-to-severe eczema.
Where are topical calcineurin inhibitors particularly useful in eczema?
In areas where long-term steroids use is contraindicated, such as the face or skin folds.
What organism is the most common cause of necrotising fasciitis?
GAS
