14 - Skin Infections and Infestations Flashcards
What is impetigo caused by and how can it be classified?
Superficial bacterial infection caused by S.Aureus (most common) or S.Pyogenes that has managed to get into a break in the skin e.g cut, eczema
- Bullous (Always S.Aureus and can infect intact skin)
- Non-bullous
What are some risk factors for impetigo?
- Eczema
- Scabies
- Surgical wound
- Chicken pox
- Insect bite
How does non-bullous impetigo present?
- Usually around the nose or the mouth but can affect other sites
- Starts as pink macule, then goes to vesicle then forms a honey crust
- Resolves on 2-4weeks with no scarring
How does bullous impetigo present?
- Small vesicles that turn into flaccid transparent bullae
- Very painful and itchy
- Eventually burst and form honey crust
- Always due to S.Aureus
- Heal with no scarring
- Usually in neonate - 2 years
What is the pathophysiology of bullous impetigo?
S.Aureus release epidermolytic enzymes that break down the proteins that hold the skin cells together
How should you manage both types of impetigo?
Non-Bullous
- Localised: first try topical antiseptic Hydrogen Peroxide 1% cream then add topical fusidic acid abx
- Widespread/Systemically unwell: oral flucloxacillin or topical fusidic acid
- Inform that it is contagious so good hygeine and keep off school until crusted over or until taken abx for 48 hrs
Bullous
- Take swabs of vesicles to get bacteria and sensitivities
- Oral flucloxacillin
- Isolate as very contagioius
- Can turn to SSSS so consider admission
What are some complications of impetigo?
- Cellulitis if the infection gets deeper in the skin
- Sepsis
- Scarring (rare)
- Post streptococcal glomerulonephritis
- Staphylococcus scalded skin syndrome
- Scarlet fever
What is folliculitis and what does it look like?
- Inflammed hair follicle due to any cause
- Tender red spot often with surface pustule
- Acne is a variant of folliculitis
What are some of the different causes of folliculities?
Infection: S.Aureus (if in deep part of follicle forms boil), HSV, P.Aeruginosa, Candida Albicans, Scabies
Irritation due to regrowing hairs: wax and shaving
Contact: moisturisers, plasters, steroid creams,
Immunosuppression
Inflammatory Disease: Lichen Planus, SLE, Acne
How do you treat bacterial folliculitis?
- Hygeine
- Oral or topical antibiotics
- Antiseptic cream
What is the difference between cellulitis and erysipelas?
- Cellulitis involves deep subcutaneous tissue and is less defined
- Erysipelas is superficial cellulitis. Affects the dermis and upper subcutaneous tissue and has a well defined, red raised border
What are some risk factors for developing cellulitis or erysipelas?
- Immunosuppression
- Wounds
- Leg ulcers
- Toeweb intertrigo
- Minor skin injury
What bacteria causes cellulitis and erysipelas?
Cellulitis: S.Aureus or S.Pyogenes
Erysipelas: Usually S.Pyogenes
What is the clinical presentation of erysipelas/cellulitis?
- Signs of inflammation: swelling, erythema, warmth, pain
- Systemically unwell with fever, malaise or rigors, especially erysipelas
- Lymphadenopathy
How is erysipelas/cellulitis managed?
- Oral flucloxacillin or benzylpenicillin. (Erythromycin if allergic)
- Rest
- Elevate affected area
- Analgesia
- Sterile dressing
What are the complications of cellulitis?
- Local necrosis
- Abscess
- Septicaemia
How does herpes simplex present?
- Grouped painful vesicles on erythematous base
- Recurrent genital (HSV2) and peri-oral (HSV1)
- Often preceded by burning/itching and flu-like symptoms like sore throat and lymphadenopathy
What are some complications of oral herpes simplex virus?
- Eczema herpeticum
- Corneal ulceration
- Erythema multiforme
- Pneumonia
- Encephalitis
How is oral herpes simplex treated?
SUPPORTIVE GENERAL MEASURES
- Analgesia for pain and fever
- Topical aciclovir not recommended
- Avoid trigger factors e.g stress, sunlight
- If severe and recurrent can give aciclovir
- Advice on reducing transmission
How is genital herpes simplex treated?
- Oral aciclovir for 5-10 days within 5 days of onset
- Self-care measures (for example topical anaesthetic, increasing fluid intake to produce dilute urine)
- Abstain from sex until lesions have cleared
- Prophylaxis aciclovir every day for 6-12 months if 6 or more attacks in a year
- Refer to specialist if pregnant or immunocompromised
What are some complications of genital herpes simplex?
- Superinfection of lesions e.g candida
- Autonomic neuropathy leading to urinary retention
- Aseptic meningitis
- Neonatal herpes simplex virus
What is the difference between varicella zoster and herpes zoster?
Varicella Zoster - Chicken Pox
Herpes Zoster - Above reactivates after lying dormant in dorsal root ganglion to produce Shingles
How does the rash in chicken pox evolve?
- Patient becomes symptomatic 10-21 days after innoculation and develops a prodromal fever, malaise, flu-like symptoms
- 24 hours later there is a generalised maculopapular rash that turns into a generalied pruritic vesicular rash
Macules –> Papules –> Vesicles –> Crust –> Hypopigmentation
How long are people with chicken pox contagious for?
- 48 hours before rash until the lesions have crusted over (usually after 5 days)
- Spread by direct contact or through infected droplets from cough or sneeze
What are some complications of chicken pox?
- Bacterial superinfection
- Dehydration
- Conjunctival lesions
- Pneumonia
- Encephalitis (ataxia presentation)
- Reye’s Syndrome
What is Reye’s syndrome?
In children after Aspirin use or following a viral infection (chickepox, influenza)
It is characterised by encephalopathy and liver impairment
How is chicken pox managed?
SELF LIMITING
- Paracetamol (NOT NSAIDS)
- Calamine lotion and antihistamines for itch
- Fluids
- Avoid high risk people e.g pregnant
- Stay off of school until crusted over
- If adult or >14 give aciclovir if <24 hours since rash onset
What type of patients are at high risk of serious infection with chicken pox?
- Infants ≤ 4 weeks old
- Immunocompromised
- Pregnant
Why is chicken pox dangerous in pregnancy?
- Fetal varicella syndrome
- Can develop varicella pneumonia
- Also check IgG for VSV. If -ve and <20 weeks then consider IVIG VSV and Aciclovir
What are some of the characterisitcs of fetal varicella syndrome?
If mum infected with VZV within first 28 weeks can result in:
- Skin scarring
- Hypoplasia of limbs
- Neurological disorders: microcephaly, learning difficulties, bladder/bowel dysfunction
- Eye disorder: microphthalmia (small eyes), chorioretinitis, cataracts
What are some risk factors for developing shingles?
- Age
- Immunosuppression (e.g steroids)
- Transplant recievers
- Autoimmune conditions
- HIV
- DM
Is shingles contagious?
Yes if someone isn’t Varicella immune it can cause them to have chicken pox
Contagious until the lesions have crusted over
How does the rash appear in shingles and what are some other symptoms that can occur with shingles?
Unilateral, erythematous, vesicular rash in a dermatomal distribution
- Paraesthesia
- Pain e.g throbbing, burning, stinging
- Flu-like symptoms e.g malaise, headache
- Hyper/hypopigmented lesions when cleared
What are some abnormal presentations of shingles and who do they occur in?
Usually in elderly or immunosuppressed
- Absence of vesicular lesions
- Prolonged rash (new lesions still occuring >7 days in immunocompromised)
- Zoster Sine Herpete (pain but no rash)
- Multiple dermatomes
What is this complication of shingles?
- Herpes Zoster Ophthalmicus: reactivation in the trigeminal nerve
- Hutchinson’s Sign: vesicular lesions on the side or tip of the nose that represents the dermatome of the nasociliary nerve (branch of the Ophthalmic division of the trigeminal nerve). This sign correlates highly with subsequent eye involvement.
- Sight-threatening as involvement of cornea
What is Ramsey Hunt Syndrome?
- Reactivation of herpes zoster in the geniculate ganglion of the facial nerve
- Facial nerve palsy associated with a vesicular rash affecting the ipsilateral ear, hard palate and anterior two thirds of the tongue
- Can cause permanent hearing loss so always check in the ears of someone with facial nerve palsy to see if it is this
How is shingles managed?
- Oral aciclovir within 72 hours of onset
- Analgesia: if mild just paracetamol, if severe give paracetamol plus neuropathic agent like amitriptylline/gabapentin
- Consider if need hospital admission for IV antivirals
- Avoid pregnant people, babies<1month, immunocompromised people until the rash has crusted over
- Good hygeine e.g washing hands, not sharing clothes
What are some of the complications of shingles?
- Scarring: hypo- or hyperpigmented areas
- Post-herpetic neuralgia
- Secondary bacterial infection
- Ramsay hunt syndrome
- Herpes zoster ophthalmicus
- Motor neuropathy
- CNS involvement: encephalitis, meningitis, myelitis
- Disseminated infection
How is Post-Herpetic Neuralgia managed?
- Conservative: wear loose clothes, consider protecting sensitive areas, cold packs
- Mild to moderate pain: simple analgesia (paracetamol with or without codeine) or topical treatments (e.g. capsacin cream)
- Uncontrolled with simple analgesia: neuropathic agents (e.g. amitriptyline, duloxetine, gabapentin, or pregabalin)
How do cutaneous warts and plantar warts (verrucae) present?
Caused by HPV 2 in keratinocytes
- Papules or nodules with a hyperkeratotic or filiform surface
- Can often coalesce (mosaic wart)
How are common warts treated?
Contagious but low transmission. High recurrence, treatment does not remove the virus!!!!!
- Often self resolve within months-2years if left alone
- If symptomatic, painful or unsightly:
- Topical salicyclic acid gel for 3 weeks (soak in water and file first)
- Cryotherapy every 3-4 weeks up to 4 cycles
- Duct tape occlusion
How does Molluscum Contagiosum present and what family of viruses causes this?
Pox Virus
- Pink or skin coloured papules with depressed central punctum
- Often in crops
- Warm, moist areas e.g. armpit or groin
- Often have a waxy, shiny look with a small central pit (umbilicated)
- Contains a white, cheesy material
- Can exhibit Köebner phenomenon
Is Molluscum Contagiosum infectious?
YES!!
- Avoid sharing towels and clothes
- Avoid scratching as can spread to other areas of the body
How is Molluscum Contagiosum treated?
- Resolve spontaneously within 18 months
- Good hygiene e.g don’t share towels
- Gentle squeezing or cryo can be tried
- If immunocompromised can have topical potassium hydroxide or benzoyl peroxide
- If secondary bacterial infection from scratching give flucloxacillin or topical fusidic acid
What is tinea incognito?
Inappropriate treatment of a tinea infection with topical or systemic corticosteroids as misdiagnosed as dermatitis
Ill-defined and less scaly lesions
Gets better but as soon as stop the steroids it comes back and worse than before
How do tinea infections typically present?
Very itchy circular or annular lesions with clearly defined, raised and scaly edge that is red in comparison with the centre
Tinea pedis: scaling and fissuring in toewebs that spreads to sole and dorsum of foot
Tinea Capitis: patches of broken hair, scaling and inflammation
Tinea Unguium: yellow nail which is thickened and crumbly
What is the name of the fungus that causes ringworm?
Trichophyton - spread by contact with infected individuals, animals or soils
What investigations should you do if somebody presents with a suspected tinea infection?
- Often just clinical diagnosis. If have tinea always check nails for fungal infection as could have spread from there
- Skin scrapings from edge of active lesion or nail clippings and send off for microscopy and culture
How is ringworm managed?
- Correct predisposing factors e.g immunosuppression, moist environment
- AVOID STEROIDS
- Can give Dactacort (miconazole and hydrocortisone) if itchy
- Skin: Terbinafine, Clotrimazole or Miconazole cream. If severe can give oral antifungals like Fluconazole, Griseofulvin and Itraconazole
- Scalp: Oral griseofulvin or Terbinafine + Ketoconazole shampoo
- Nail: Amorolfine Nail Lacquer (6 months fingernails, 9-12 months toenails) or Oral Terbinafine for 3-6 months
What are some of the side effects with Terbinafine?
NEEDS LFT MONITORING WHILST TAKING THIS
- Rash
- Loss of appetite
- N+V
- Muscle or joint pain
What is some general advice you can give to patients with ringworm to stop them from spreading it and catching it again?
- Wear loose clothing
- Keep the affected area clean and dry
- Avoid sharing towels, clothes and bedding
- Use a separate towel for the feet with tinea pedis
- Avoid scratching and spreading to other areas
- Wear clean dry socks every day
How does candidiasis present?
Mucosal: white plaques that can be scraped off
Skin: erythema with papules/pustules and satellite lesions in flexures
How is candida treated?
- Address predisposing factors e.g good diabetic control, immunosuppression, loose clothing
- Skin: Topical Clotrimazole
- Mouth: Topical Nystatin or Miconazole gel
- Vagina: Oral or Pessary Fluconazole and topical Clotrimazole
What fungus causes Pityriasis Versicolour and how does it present?
Malassezia Fufur
- Dry Scaly pale brown/hypopigmented patches on upper trunk/back that fail to tan on sun exposure due to production of azelaic acid which inhibits melanogenesis
- Asymptomatic - clinical Dx can be confirmed with skin scrapings
How is Pityriasis Versicolour treated?
- Imidazole creams BD e.g clotrimazole
- 2% ketoconazole shampoo daily for 5 days (wash off after 5min)
- Relapses are frequent
What is scabies caused by and how does it spread?
- Sarcoptes scabei parasite
- VERY CONTAGIOUS
- Mites burrow under the skin and leave track marks (short wavy grey or red line). They lay larvae which then hatch after about 8 weeks which causes hypersensitivity reaction and rash
- Can be spread by direct contact e.g sharing bed with anyone, holding hands
How does scabies present?
- Very itchy papules/pustules (more itchy at night)
- Burrow marks
- Excoriations
- Usually between finger webs but can spread over whole body, usually to wrist flexures, axillae, abdomen
- In children often affects palms and soles
How is scabies diagnosed?
- Typically clinical from burrows and other household members with same rash
- Look at burrow under dermatoscope and mite may show hangglider sign
- Skin biopsy but often negative as taken from inflammatory rash rather than burrow
How is scabies managed?
General
- Treat all household members and sexual partners even if asymptomatic
- Hygiene advice e.g all clothes, bedclothes, towels in contact with scabies need to be washed on a hot wash to destroy the mites. Thorough hoovering of carpets and furniture
Specific
- Permethrin cream
- Oral ivermectin as a single dose a week later if severe or crusted scabies
- Crotamiton cream and Chlorphenamine at night as itching can occur for up to 4 weeks after treatment and treatment can make itching worse
How do you advice somebody to use Permethrin cream for the treatment of scabies?
- Take a warm bath and soap the skin, scrub the fingers and nails with a firm brush. Dry your body.
- Apply Permethrin (or malathion 0.5% liquid) to all body parts from the neckdown, including soles. Avoid the eyes! Save a small amount of cream and use this to reapply to any body part (eg hands) that is washed before the 12h is up.
- Wash off after 8-12h
- Wash all sheets, towels, and clothing in a hot wash.
- Repeat treatment after 7 days to kill any eggs that have hatched
- Treatment may worsen itch for 2 weeks so use calamine lotion or crotamiton cream
What is crusted scabies (Norwegian scabies)?
- Serious infestation with scabies in patients that are immunocompromised or elderly
- Extremely contagious as may have one million mites on skin
- Rather than individual spots and burrows, they have patches of red skin that turn into scaly plaques, looks like psoriasis
- Immunocompromised patients may not itch as they do not mount an immune response to the infestation.
What is head lice caused by and how is it spread?
- Pediculus Humanus Capitis parasite
- Spread by head to head contact or sharing brushes/towels
- Nits are hatched eggs that appear white. Before hatching they are brown so difficult to see
How do headlice present?
- Can be asymptomatic and just see the lice or nits in the scalp
- Itchy scalp with paular rash on the nape of the neck and behind the ears
How are headlice treated?
All options require 2 treatments, 7 days apart to kill any lice that have hatched. Treat head to head contacts only if they have live lice
- Malathion 0.5%: Apply to hair from roots to tips. Leave overnight, then shampoo and rinse off.
- Dimeticone 4%: Leave overnight, then shampoo and rinse off. Resistance is a problem.
- Wet Combing: for detection and treatment
What is the likely cause of this man’s pruritus?
Iron deficiency anaemia
What investigation should you do for this lady?
Skin Patch Testing (Type 4 hypersensitivity)
(Skin prick would be no good)
What is the most likely diagnosis?
What is the most likely diagnosis?
Type of peripheral neuropathy which is characterized by simultaneous or sequential involvement of individual non-contiguous nerve trunks, either partially or completely, evolving over days to years and typically presenting with acute or subacute loss of sensory and motor function of individual nerves.
What is a surgical third nerve palsy?
What is the treatment for endopthalmitis?
Intravitreal vancomycin
If sporadic wouldn’t be bilateral and presents closer to 24 months
