(PM3A - Scabies, Lice, Boils, Impetigo, Wound Healing Flashcards
What is scabies?
Infestation of the skin with a mite
What causes scabies?
Sarcoptes scabiei
What do scabies live
In burrowed tunnels in the stratum corneum
How long are the burrows of scabies?
A few mm-1cm long
Where are scabies most often found on the body?
Between the fingers + on the wrists
Waistline + genitals
How are scabies transmitted?
Direct contact
Animal transmission can occur
What is the primary risk factor for scabies?
Crowded conditions
e.g. schools/ homeless shelters
How do scabies infections present?
Pruritic lesions - worse at night
Erythematous papules
What types of scabies are there?
(1) Classic scabies
(2) Crusted (Norwegian) scabies
(3) Nodular scabies
(4) Bullous scabies
(5) Scalp scabies
(6) Scabies incognito
How is an infection of crusted (Norwegian) scabies caused?
Impaired immune system in a classic scabies infection
What is nodular scabies?
More common in infants + young children
Likely due to a hypersensitivity to these organisms
What are bullous scabies?
Occurs in children + elderly
When do scalp scabies occur?
Infants + immunocompromised patients
Appear similar to seborrhoeic eczema
What causes scabies incognito?
Application of topical corticosteroids
What is scabies incognito?
Widespread atypical presentation of scabies
How are scabies diagnosed?
(1) Examination
(2) Skin scrapings
What is the first line treatment for scabies?
Scabicides
e.g. permethrin
Applied to entire body from neck down, washed off after 8-14hrs, repeat after 7 days
What is permethrin used to treat?
Scabies infections
How does application of permethrin differ in infants and young children?
Should be applied ALSO to head + neck
AVOID periorbital + perioral regions
When is lindane contraindicated for scabies infections?
(1) <2yrs old
(2) Seizure disorder
Potential neurotoxicity
What is the treatment for crusted (Norwegian) scabies?
Ivermectin
When is ivermectin indicated ahead of permethrin for scabies?
Crusted (Norwegian) scabies
Patients who do not respond to topical treatment
Who/ what should be treated in a scabies infection?
(1) Patient
(2) Close contacts
(3) Personal items - store for 3 days/ washed
What is the treatment for pruritus?
Corticosteroid ointments
Oral antihistamines
Define pruritus?
Severe itching of the skin
How long can symptoms and lesions be expected to take to heal following treatment?
Up to 3 weeks
What is pediculosis?
Lice
What is another name for lice?
Pediculosis
What are lice?
Wingless blood-sucking insects
2-5mm in length
Infest scalp, pubis, body, or eyelashes
Where can lice infections occur?
(1) Scalp
(2) Eyelashes
(3) Body
(4) Pubis
How long can lice live without a human host?
Up to 30 days
How are head lice transmitted?
Close contact
How are body lice transmitted?
Cramped + close conditions
How are pubic lice transmitted?
Sexual contact
What are pubic lice called?
Crabs
What is the correct term for crabs?
Pubic lice
How can lice cause contraction of other diseases?
Lice can act as vectors
At what age is head lice most common?
Girls aged 5-11yrs
In what patient group are head lice most uncommon?
Afro-Caribbeans
How many lice are commonly present to cause an active infestation?
<20 lice
What is the main symptom of head lice infestations?
Severe pruritus - skin itching
How is a head lice infestation diagnosed?
Combing through wet hair with fine-toothed lice comb
Where on the scalp are head lice most often found?
Back of head
Behind ears
What are nits?
Greyish-white eggs
Fixed to the base of hair shafts
Baby head lice
What are higher in number on the scalp during a lice infestation, nits or lice?
Nits
Where do body lice primarily live?
Bedding/ clothing
Where are body lice most commonly found?
Crowded conditions
e.g. barracks/ low socio-economic status
How are body lice transmitted?
Sharing contaminated clothing/ bedding
What is the most significant symptom of body lice?
Intense pruritus - skin itching
What can be observed in a body lice infestation?
Small red puncta caused by bites
How is a body lice infestation diagnosed?
Demonstration of nits/ lice in clothing
What is the treatment for head lice?
(1) Treatment of all family members
(2) Mechanical removal (avoids irritants)
(3) Comb every 4 days for 2 weeks - due to hatching of nits
What medications can be used for treatment of head lice?
(1) Permethrin
(2) Dimeticone (4%)
(3) Malathion (0.5%)
How should dimeticone 4% be applied?
(1) Apply to dry hair + scalp
(2) Allow to dry naturally
(3) Wash off after 8hrs
(4) Repeat after 7 days
How should malathion 0.5% be applied?
(1) Apply to dry hair + scalp
(2) Allow to dry naturally
(3) Wash off after 12hrs
(4) Repeat after 7 days
What is the treatment for body lice?
Treatment of pruritus
Treatment of any secondary infection
Why is there no direct treatment for body lice?
Body lice live in clothing/ bedding, not on the body
What is the treatment for pubic lice (crabs)?
Malathion 0.5%
Apply over whole body + allow to dry naturally
Wash off after 12hrs
Repeat after 7 days
How is a lice infestation of the eyelashes treated?
Petrolatum ointment applied to eyelids
Apply TDS-QDS
Duration of 8-10 days
What are boils?
Skin abscesses
What other names for boils?
Furuncles
Carbuncles
What causes boils?
Tender nodules caused by Staphylococcal infection
Often of the hair follicle
What are furuncles?
Type of boil
Common on face/ neck/ breasts/ buttocks
Appear as nodules/ pustules
What are carbuncles?
Type of boil
Cluster of furuncles
Connected subcutaneously
What are the common risk factors for boils?
(1) Bacterial colonisation of skin
(2) Hot/ humid climates
(3) Occlusion/ abnormal follicular anatomy
Which patient groups are more predisposed to boils?
(1) Obese
(2) Immunocompromised
(3) Diabetic
(4) Elderly
How are boils diagnosed?
Examination
Cultures should be obtained for single furuncles on nose/ face + multiple furuncles + immunocompromised patients
What is the treatment for a single boil lesion?
Intermittent hot compresses
To allow it to drain
What is the treatment for a furuncle in the nose/ central face area?
Topical antibiotics
When are systemic antibiotics required for boils?
(1) Larger lesions
(2) Lesions that do not respond to topical care
(3) Evidence of expanding cellulitis
(4) Immunocompromised patients
How can recurrence of furuncles be prevented?
Application of liquid soap
i.e. chlorhexidine gluconate with isopropyl alcohol
What is impetigo?
Superficial skin infection with crusting
Caused by Streptococci/ Staphylococci
Which microorganism causes impetigo?
Staphylococci/ Streptococci
How does an impetigo infection start?
Can follow any break in the skin
What are some risk factors for impetigo?
(1) Moist environment
(2) Poor hygiene
(3) Chronic nasal carriage of staphylococci
How does impetigo present?
(1) Clusters of vesicles/ pustules
(2) Develop a honey-coloured crust
What is ecthyma?
Ulcerative form of impetigo
How does ecthmya present?
Small + shallow
Punched out ulcers
Thick + brown/ black crusts
Erythema (redness)
What is an issue with pruritus of impetigo?
Scratching can spread infection
How are impetigo and ecthyma diagnosed?
(1) Characteristic appearance
(2) Cultures of lesions when patient not responsive to initial therapy
(3) Nasal culture for recurrent impetigo
What is the treatment for impetigo and ecthyma?
Localised infection treated with fusidic acid 2%
TDS/ QDS
How is an impetigo/ ecthyma infection caused by MRSA treated?
Topical mupirocin 2%
TDS for 10 days
How is an extensive impetigo/ ecthyma infection treated?
Oral
Flucloxacillin/ clarithromycin
What is photosensitivity?
Poorly understood
Reaction of skin to sunlight
Likely to involve immune system
What are some symptoms of photosensitivity?
(1) Redness
(2) Rash
(3) Urticaria - hives
Can also lead to dizziness/ wheezing etc
Can drugs increase risk of photosensitivity?
Yes
Phenothiazines
What is the treatment for photosensitivity?
Depends on cause
(1) Unusual reaction w/ brief exposure = skin disorder/ systemic disease
(2) Use of chemicals + exposure = Topical corticosteroids + avoid chemical
What is drug-induced photosensitivity?
Increased sensitivity to sunlight due to exposure to certain drug/ chemical
What are the types of drug-induced photosensitivity?
(1) Phototoxicity
(2) Photoallergy
What is phototoxicity?
Light-absorbing compounds directly generate inflammatory mediators + free radicals
Causes tissue damage + pain + erythema
Typically caused by topicals or ingested agents
ONLY present on sun-exposed skin
What is a photoallergy?
Type 4 (cell-mediated) allergic response
Light absorption causes structural changes to drug/ chemical
Drug then binds to a tissue protein and acts as a hapten
Prior exposure is required
What are some common causes of photoallergic reactions?
(1) Aftershave lotions
(2) Sun creams
(3) Sulfonamides
What are the symptoms of a photoallergic reaction?
(1) Erythema - redness
(2) Pruritus - itching
Sometimes vesicles
What are burns?
Injuries of the skin/ other tissue
Thermal/ chemical/ radiation/ electrical contact
How are burns classified?
By depth + % of body surface area involved
What type of burn is sunburn?
Radiation burn
How do burns damage the skin?
Protein denaturation + coagulation necrosis
Can get a bacterial infection through damaged epidermis
How do burns cause heat loss?
Impaired thermoregulation due to damaged dermis
What is the risk with a higher percentage of burnt surface area of the body?
Increased risk of developing systemic complications
What are the risk factors for severe complications/ death from burns?
(1) >40% body surface area
(2) >60yrs old
(3) <2yrs old
(4) Simultaneous major trauma/ smoke inhalation
How is a first degree burn characterised?
Red + blanch markedly w/ light pressure
Painful + tender
Limited to epidermis
How are second degree burns characterised?
Partial thickness
Involves part of the dermis
Sub-divided into superficial + deep
What is a superficial 2nd degree burn?
Upper half of dermis
2-3 weeks heal time
Rarely scar unless infected
Intense pain + tender
Vesicle development within 24 hours
What is a deep 2nd degree burn?
Bottom half of dermis
> 3 week heal time
Scarring is common
Do not blanch
LESS painful than superficial burns
Burns are very dry
How are third degree burns classified?
Full thickness
Extend through entire dermis + into underlying fat
How are burns treated?
Examination + treatment as soon as patient is stable
Estimate extent of burn (handprint = ~1%)
Remove clothing covering burn
Flush chemicals off (powders are brushed)
Acid/ alkali burns with water for 20 mins
> 15% surface area given IV fluids
Clean burn wound + apply topical antibacterial salve + sterile dressing
What is an example of a topical antibacterial salve applied for burns?
Silver sulphadiazine
How is the ongoing treatment of burns managed?
Daily changing of dressings
Complete cleaning of burn with water
Application of a new layer of antibacterial salve
Surgery/ grafting for all 3rd degree burns and those that do not heal <3 weeks
Where is a skin graft often taken from?
Healthy skin, e.g. thigh
Skin graft is cut into a mesh
What happens to skin that is taken for a graft before being transplanted?
Graft is cut into a mesh
To cover larger surface area
Why are skin grafts cut into a mesh prior to retransplantation?
To increase surface area
Can increase 2-3x
What is a wound?
A physical break in the skin
Tear/ cut/ erosion/ puncture/ ulcer
Break in the skin barrier
What are some types of trauma wound types?
(1) Abrasion/ graze - superficial, epidermis scraped off
(2) Laceration - irregular tear
(3) Avulsion - removal of all skin layers by abrasion
(4) Incision - regular slice with clean sharp object
(5) Puncture - e.g. needle/ nail
(6) Amputation
How many types of wound classification are there?
4 types
(1) Necrotic
(2) Sloughy
(3) Granulating
(4) Epithelialising
What is a necrotic wound?
Dead/ ischaemic tissue
Usually black + covered with dead epidermis
What is a sloughy wound?
Often yellow
Due to cellular debris/ fibrin/ serum exudate/ bacteria
What is a granulating wound?
Typically pink/ red
Highly vascularised
Irregular + granular appearance
What is an epithelialising wound?
Cells migrate from wound edges
Start the process of re-epithelialisation
See a pink wound bed
What are the stages in wound healing?
(1) Haemostasis
(2) Inflammation
(3) Proliferation
(4) Maturation/ remodelling
What is the process of haemostasis?
The first process in wound healing
(1) Vasoconstriction following injury
(2) Platelet aggregation
(3) Coagulation cascade
(4) Haemostatic plug/ clot seal damaged vessel
What is inflammation?
Redness/ heat/ pain/ swelling
Typically 4-5 days
Initiates healing process
Stabilises wound through platelet activity
Neutrophils/ monocytes/ macrophages control bacterial growth
Red colour + warmth caused by capillary blood system increasing circulation
What is proliferation?
Begins within 24hrs of initial injury
Continues for up to 21 days
Characterised by:
(1) Epithelialisation
(2) Granulation
(3) Collagen synthesis
What is granulation?
Formulation of new capillaries - angiogenesis
‘Beefy’ red tissue
Bleeds easily
Fibrous connective tissue replaces fibrin clot
Grows from the base of the wound
What is epithelialisation?
Formation of epithelial layer
Seals + protects wound from bacteria + fluid loss
Must have a moist environment for faster growth
Initially fragile - can be easily destroyed
What is collagen synthesis?
Creation of a support matrix for new tissue
Provide structural strength
Oxygen + iron + vitamin C + magnesium + zinc + protein are VITAL for collagen synthesis
The actual rebuilding of the skin barrier
What is wound contraction?
Large wounds can be 40-80% smaller after contraction
Can continue for weeks - even after wound has been completely re-epithelialised
Usually does not occur symmetrically
What is maturation?
Final stage of wound healing
Begins ~21 days after injury
Can continue for ≤2 years
Begins when collagen synthesis + degradation equalise
Type 3 collagen is gradually replaced with Type 1 collagen
Collagen fibres are rearranged and cross-linked (aligned along tension lines)
What type of collagen is produced in initial collagen synthesis? What happens to this?
Type 3 collagen
Gradually replaced with Type 1 collagen during maturation
What are Langer’s lines?
Direction that skin will split when a human cadaver is hit with a spike
Describe the changes to the tensile strength of the wound in maturation/ re-modelling.
Tensile strength increases
~50% of normal tissue’s tensile strength after 3 months
~80% of normal tissue’s tensile strength after full healing
What are the different types of wound healing?
(1) Primary healing - healing by first intention
(2) Secondary healing - healing by secondary intention
(3) Delayed primary healing - healing by tertiary intention
What is primary wound closure?
Wound edges re-approximated to be adjacent to each other
Most surgical wounds heal this way
Closure performed with sutures/ staples/ adhesive tape
Minimises scarring + infection risk
What is secondary wound closure?
Wound is allowed to granulate
Wound may be packed with gauze
Granulation causes broader scar than first intent
Healing can slow due to drainage from infection
Daily wound care required - encourage wound debris removal to allow for granulation formation
Prevents haematoma development
What is delayed primary healing?
Wound is purposely left open
Wound cleaned + debrided + observed
4th day phagocytosis of contaminated tissues
Wound closed surgically after 4-5 days
Can result in significant scarring if wound is not cleaned effectively
What are scars?
Areas of fibrous tissue
- Natural part of the healing process
- Result from wounds
Describe the collagen arrangement of normal skin.
‘Basket-weave’
Describe the collagen arrangement of scar tissue.
Highly orientated
Weaker to future trauma, e.g. UV radiation
What does not regrow in scar tissue?
(1) Sweat glands
(2) Hair follicles
What happens if myofibroblasts are not cleared by apoptosis?
May get keloid/ hypertrophic scars
How are myofibroblasts (from scarring) removed?
By apoptosis
What is a hypertrophic scar?
Over-production of collagen
Scar raised above surface
Typically red
Less common following surgery
More common for wounds closed by secondary intent
What is a keloid?
Overgrowth of collagen
Formation of rubbery/ shiny nodules
Pink/ red/ brown
Can grow into large benign tissue
Completely harmless + non-cancerous
Can be itchy/ painful
Most common on shoulders/ chest
What is an atrophic scar?
Sunken recess in the skin
Pitted appearance
Caused when underlying skin structures are lost
- e.g. muscle/ fat
Often with acne/ chickenpox
What are stretch marks?
Type of scar
AKA. striae
Common during pregnancy/ weight gain/ growth spurts
Occur when skin is put under tension during healing process
What is the purpose of scar treatment?
For cosmetic purposes
How can scars be treated?
(1) Chemical peels: for superficial scars
(2) Filler infections: for atrophic (sunken) scars
(3) Dermabrasion: Remove top layer of scar tissue
(4) Laser:
- Can heat + redistribute collagen in keloids (non-ablative)
- Can remove outer skin layers (ablative) not for keloids
(5) Radiotherapy: Low dose can help keloids
- Not recommended - significant adverse effects
(6) Ointments + pressure dressings
- No strong evidence of support
(7) Steroids: Inject steroid into scar
- Can thin + soften the scar
(8) Surgery: Remove scar (keloids recur 45%)
Following surgical removal, what is the recurrence percentage of keloid scars?
45%
