15. Skin Infections Flashcards
(35 cards)
Outline the aetiology pathophysiology of cellulitis + erysipelas
Ae = Group A streptococci (pyogenes), Staph aureus
- RF: insect/spider bite, blistering, animal bite, tattoos, pruritic skin rash, surgery, athletes’ foot, eczema, IV drugs
CELLULITIS =
- Infection affecting the lower dermis and subcut fat
- Typically lasts 7-10 days
ERYSIPELAS =
- acute superficial form of cellulitis - involves dermis and upper subcut tissue
List the signs and symptoms of cellulitis
Erythema that increases in size - most common lower limb
Irregular borders (distinguished from erysipelas by well-defined red raised border)
Hot to touch
Swollen skin, blistering, erosion, ulcers, abscess, dimpling
Pain
General fever
Tiredness
How should cellulitis be investigated?
Clinical Dx
Wound swab - C+S
US - rule out DVT
How should cellulitis be managed?
Abx - cephalexin, amoxicillin, erythromycin
Analgesia
Surgical drainage of abscess
Sepsis 6 - if it has devel this far
Comp = abscess, nec fasciitis, sepsis, gas gangrene, endocarditis
What are the causes and pathophysiology of impetigo?
Bacterial - staph aureus, strep pyogenes
Involves superficial layers of skin
Spread via direct skin-to-skin contact
Duration - < 3 weeks
What are the signs and symptoms of impetigo?
Often begins as red sore near the nose or mouth, painful itchy yellowish crusts, lymphadenopathy
How should impetigo be managed and what are its possible complications?
Abx - topical = mupirocin, fusidic acid, oral = cephalexin
Comp =
- Cellulitis
- Post-streptococcal glomerulonephritis
Outline the aetiology + pathophysiology of folliculitis
Chronic infection of hair follicles, can also be damaged
What are the signs and symptoms of folliculitis?
Small red bumps, white headed pimples, itchiness
How should folliculitis be managed?
Topical antiseptic (tea tree oil), topical Abx (zineryt - topical erythromycin), fungal - fluconazole
Outline Scabies
Scabies is an infestation of tiny mites that burrow into the epidermis of the skin
- may have Hx of contact
- pruritus worse at night
LINEAR burrows or rubbery nodules
<2y = rash on head, neck, palms, soles
>2 y = rash on hands, between fingers, wrists, belt line, thighs, naval, groin, chest, armpits
Mx = Permethrin 5% cream for 8-10h then wash off, antihistamine
- all linin, family members, friends and sexual contacts should be treated at the same time whether they are itchy or not
Outline head lice
Tiny parasitic insects that can infest the skin
Spread from person to person by close body contact, and by shared clothes and other personal items
S+S = itching, visible eggs/nits
Mx = medicated cream rinse or shampoo, fine-tooth comb, checking family, washing all bedding and clothing in hot water
What is the aetiology of varicella (chicken pox)?
Aetiology = varicella zoster virus (VZV)
How does varicella present?
Small, erythematous macules appear on the scalp, face, trunk, and proximal limbs, which progress over 12–14h to papules, clear vesicles (which are intensely itchy), and pustules
Crusting occurs usually within 5d of the onset of the rash, and crusts fall off after 1–2w
Headache, loss of appetite, tiredness, fever
Onset = 10–21 days after exposure
Duration = 5–7 days
Outline the management of a varicella infection
Topical calamine lotion - alleviate itch
Chlorphenamine - itch associated with chickenpox for people 1 year of age or older.
Paracetamol - if pain or fever are causing distress
Oral acyclovir - for those who presents within 24 hours of rash onset
What is staph scaled skin syndrome, its presentation and a DDx?
Staph (coag +ve) produces an exfoliative toxin that causes the outer layers of skin to blister and peel, as if they’ve been doused with a hot liquid
Most common in children under 6
S+S = fever, irritability, widespread erythema, within 24-48h fluid-filled blisters form; rupture easily, leaving an area that looks like a burn, tissue paper-like wrinkling of the skin, Nikolsky sign (top layers of the skin slip away)
Mx = Abx, analgesia
DDx = drug hypersensitivity, viral exanthemas, scarlet fever, thermal burns, epidermolysis bullosa, toxic epidermal necrolysis
Outline the aetiology and pathophysiology of syphilis
Ae = STI - spirochete Treponema pallidum
Path = transmission sexually/blood/vertically, symptomatic and asymptomatic stages, cutaneous lesions where T. pallidum uses its spiral shape to twist into the skin
How does syphilis present?
Congenital = maculopapular rash, vesiculobullous lesions, mucous patches, condyloma lata, or as rhinitis (inflamed mucous membrane in the nose causing snuffles)
PRIMARY
- Solitary, small firm red painless papule on the genital area quickly becomes a painless ulcer with a well-defined margin and an indurated base
SEC
- Rash trunk, palms, soles (rough, red or reddish-brown papules or plaques)
- Greyish-white, moist plaques occur in the groin, inner thighs, armpits, umbilicus, or under the breasts; these are called condyloma lata
- Raw mucous surfaces
LATENT
- Asymptomatic
TERT (30-40y later)
- Gumma: solitary granulomatous lesion with central necrosis
How should syphilis be Ix and Mx?
Ix = serology or dark-field microscopy or by treponemal polymerase chain reaction (PCR) testing
Mx = benzathine or procaine penicillin injection
Outline herpes simples
Ae = HSV1 (oral), HSV2 (genital)
- often triggered by a febrile illness
- after the primary ep, HSV resides in latent state in spinal dorsal root nerves
S+S =
- HSV1: whitish vesicles evolve to yellowish ulcers on the tongue, throat, palate and inside the cheeks, LN, fever
- HSV2: painful vesicles, ulcers, redness and swelling, inguinal LN
Ix = culture, viral swab PCR
Mx = acyclovir
Comp = eczema herpeticum
Outline syphilis
Ae/path = VZV remains dormant in dorsal root ganglia nerve cells in the spine for years before it is reactivated and migrates down sensory nerves to the skin to cause herpes zoster
S+S = blistering red papules, dermatomal distribution, can become pustular then crusting
Ix = clinical Dx
Mx = acyclovir started 1-3d within start of Sx, rest, pain relief, protective ointment, oral Abx (sec infection)
What is molluscum contagiosum
Ae = poxvirus, via skin-to-skin, towels, scratching/shaving, sexual
S+S = localised clusters of epidermal papules, white, pink or brown, waxy, shiny look with a small central pit
Ix = clinic Dx
Mx = self-limiting, cryotherapy, curettage or electrodessication, laser ablation
***advice and guidance to not share towels, flannels or clothing, avoiding squeezing spots, avoiding sharing baths and keeping affected areas covered
Outline the different tinea infections
Fungus in the horny layer of skin, hair, and nailbeds called dermatophytes
Types:
1) Tinea pedis (athletes foot): white, scaling, itchy, blisters (Tx: dry feet, topical AF)
2) Tinea cruris (Jock itch): red, ring-like patches in the groin area (Tx: systemic AF)
3) Tinea capitis (scalp): scaly, itchy, hair loss (Tx: systemic AF)
4) Tinea corporis (ringworm): trunk/limbs, circular scaly edge (Tx: topical AF)
5) Tinea unguium (nail): thickened, deformed, yellowing (Tx: topical AF)
Mx = antifungals 4-8w +/- shampoo, Tx pet if infected
Outline Candidal intertrigo
Ae = superficial skin-fold infection caused by the yeast, candida
- triggered by combination: hot, damp, skin friction, immunosuppression
S+S = erythematous and macerated plaques with peripheral scaling, often associated superficial satellite papules or pustules
Ix = fungal microscopy and culture of skin swabs and scrapings
Mx =
- address RF: weight loss, blood glucose control and avoidance of tight clothing, cool and moisture-free skin
- clotrimazole cream
