common skin infections Flashcards
what is tinea capitis
An infection of scalp hair follicles and the surrounding skin, caused by dermatophyte fungi
Tinea capitis is a fungal infection of the scalp, involving both the skin and hair. It is also known as scalp ringworm.
common organisms to cause tinea capitis
Microsporum canis
Trichophyton tonsurans.
classification for tinea capitis
Ectothrix (dermatophyte infection remains confined to the hair surface) e.g. M. canis
Endothrix (dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell) e.g. T. tonsurans, most common in the UK
Favus: Honeycomb destruction of hair shaft
tinea capitis seen commonly in who
Most commonly seen in healthy preadolescent children and immunocompromised adults
clinical features of tinea capitis
Scale, bald patches, regional lymphadenopathy
Kerion (abscess caused by fungal infection)
what Ix one ca do for tinea capitis
1) Wood’s lamp
Some dermophyte fungi e.g. ectothrixMicrosporumspecies demonstrate bright green fluorescence of infected hairs
Others don’t (e.g. nonfluorescent Trichophyton infection)
2) Dermoscopy
Black dot hairs, comma shaped hairs, cork-screw hairs
3) Specimens for microscopy + culture (diagnostic)
Scalpel scraping, hair pluck, brush or swab as appropriate to the lesion
risk factors of tinea capitis
animal contact household crowding lower socioeconomic status warm humid environments contact sport.
complications of tinea capitis
alopecia
scarring alopecia - bald patches
erythema nodosum
ID reaction - get after starting the antifungal treatment
what would you see under a dermoscope for tinea capitis
Comma hairs
Corkscrew hairs
Zigzag hairs
Barcode-like (Morse code-like) hairs
Bent hairs.
tinea capitis DD
Alopecia areata and trichotillomania; cause patchy alopecia but are not scaly
Seborrhoeic dermatitis, atopic dermatitis, and scalp psoriasis; may mimic non-inflammatory tinea capitis, but the scale is usually more diffuse
Discoid lupus erythematosus and lichen planopilaris; cause scarring alopecia
tinea capitis management
4 weeks of systemic medication
Prescribe either oral griseofulvin (licensed) or oral terbinafine (off-label) empirically until culture results are available.
If the person lives in an urban area, start treatment with terbinafine for 4 weeks. - trichophyton tonsurans
If the person lives in a rural area, start treatment with griseofulvin for 4–8 weeks - griseofulvin
selenium sulfide or ketoconazole shampoo to be used at least twice weekly for 2–4 weeks, or an imidazole cream (in children less than 5 years of age) to be used daily for one week.
what is tinea corpis
Trunk and limbs
Itchy circular/annular rash with a clearly defined raised and scaly edge
Usually treat with topical antifungals; oral antifungals if unsuccessful
what is tinea cruris
involvement of groin and natal cleft
See management of Tinea cruris; may also benefit from topical corticosteroids for pruritus
what is tinea pedis and how does it look
athlete’s foot
moist scaling and fissuring in toewebs
spreads to sole and dorsal aspect of the foot
what is tinea manuum
Infection of the hand
Less common than infection of the foot
Scaling and dryness in the palmar creases
what is tinea unguium
ONYCHOMYCOSIS
Infection of the nail
Yellow discolouration, thickened and crumbly nail
Can lead to nail dystrophy
Mild infections can be managed with topical antifungals, oral antifungals often required for cure
What is tinea incognita
Inappropriate treatment of tinea infection with topical or systemic corticosteroids
Original infection also extends
Management: Cessation of steroid and standard antifungal treatment
features of cellulitis
- Dimpled skin (peau d’orange)
- Warmth
- Blistering
- Erosionsand ulceration
- Abscessformation
- Purpura:petechiae,
ecchymoses, or haemorrhagicbullae
Systemic features
Fever
Malaise
Lymphangitis
what is cellulitis
A common bacterialinfectionthat involves the deep subcutaneous tissue
localisedarea of red, painful, swollen skin, andsystemicsymptoms
causes of cellulitis
Streptococcus pyogenes, Staphylococcus aureus
risk factors of cellulitis
Breaks in skin barrier: Wounds, ulcers, athlete’s foot, insect bites, IVDU, pressure sores
Poor venous flow / lymphatic drainage
Immunosuppression
Diabetes, chronic kidney disease, chronic liver disease
Obesity, pregnancy, alcoholism
investigations for cellulitis
Bloods: Inflammatory markers, Anti-streptococcal O titre (ASOT)
increase in CRP, leukocytosis
Skin swab
Imaging if required
management for cellulitis
Systemic antibiotics (usually oral); often penicillin-based e.g. Flucloxacillin, benzyl
Potential alternatives if penicillin-allergic: Clindamycin, Doxycycline, Vancomycin
complications of cellulitis
Necrotisingfasciitis
Gasgangrene
Severesepsis
Infection of other organs, e.g. osteomyelitis, meningitis, pneumonia
Endocarditis
what is erysipelas
Superficial form of cellulitis: Affects the upperdermisand extends into the superficial cutaneouslymphatics
differentials of cellulitis
Eczema/dermatitis due to stasis, contact factors
Fungal infection eg tinea corporis, tinea pedis Drug eruption Psoriasis Lipodermatosclerosis Thrombophlebitis Insect bites and stings Radiation damage following radiotherapy Inflammatory breast cancer (carcinoma erysipeloides).
how to differentiate between erysipelas and cellulitis
erysipelas - well defined border
clinical features of erysipelas
sharp and raised border
It is bright red, firm and swollen. It may be finely dimpled (like an orange skin).
It may be blistered, and in severe cases may become necrotic.
Bleeding into the skin may cause purpura.
Cellulitis does not usually exhibit such marked swelling but shares other features with erysipelas, such as pain and increased warmth of affected skin.
In infants, it often occurs in the umbilicus or diaper/napkin region.
Bullous erysipelas can be due to streptococcal infection or co-infection with Staphylococcus aureus (including MRSA).
abrupt in onset and often accompanied by fevers, chills and shivering.
Erysipelas predominantly affects the skin of the lower limbs, but when it involves the face, it can have a characteristic butterfly distribution on the cheeks and across the bridge of the nose.
complications of erysipelas
- Persistence of risk factors
- Lymphatic damage (hence impaired drainage of toxins).
RARE
Abscess
Gangrene
Thrombophlebitis
Chronic leg swelling
Infections distant to the site of erysipelas
Infective endocarditis (heart valves)
Septic arthritis
Bursitis
Tendonitis
Post-streptococcal glomerulonephritis (a kidney condition affecting children)
Cavernous sinus thrombosis (dangerous blood clots that can spread to the brain)
Streptococcal toxic shock syndrome (rare).
skin manifestations of SLE
photosensitive ‘butterfly’ rash
discoid lupus
alopecia
livedo reticularis: net-like rash
what is pityriasis versicolor
superficial cutaneous fungal infection caused by Malassezia furfur
features of pityriasis versicolour
- most commonly affects trunk
- patches may be -hypopigmented, pink or brown (hence versicolor). May be more noticeable following a suntan
- scale is common
- mild pruritus
predisposing factos of pityriasis versicolor
- occurs in healthy individuals
- immunosuppression
- malnutrition
- Cushing’s
management of pityriasis versicolor
topical antifungal =ketoconazole
fail
scrapings + oral itraconazole
when can a child return to daycare if they have impetigo
Patients may return to school or work when they are no longer contagious which is when all lesions have crusted over or 48h after treatment starts
how long must child wait to return to skl if they had measles or rubella
4 days following the onset of the rash
what is impetigo
- superficial bacterial skin infection usually caused by either Staphylcoccus aureus or Streptococcus pyogenes.
primary infection or a complication of an existing skin condition such as eczema (in this case), scabies or insect bites.
where does impetigo tend to occur
anywhere on the body but lesions tend to occur on the face, flexures and limbs not covered by clothing.
how is impetigo spread
Spread is by direct contact with discharges from the scabs of an infected person.
The bacteria invade the skin through minor abrasions and then spread to other sites by scratching.
Infection is spread mainly by the hands, but indirect spread via toys, clothing, equipment and the environment may occur.§
incubation period for impetigo
4-10 days
features of impetigo
‘golden’, crusted skin lesions typically found around the mouth
very contagious
management for impetigo
1) hydrogen peroxide 1% cream for ‘people who are not systemically unwell or at a high risk of complications’
2) topical antibiotic creams:
topical fusidic acid
topical mupirocin should be used if fusidic acid resistance is suspected
MRSA is not susceptible to either fusidic acid or retapamulin. Topical mupirocin should, therefore, be used in this situation
Extensive disease
oral flucloxacillin
oral erythromycin if penicillin-allergic
stay off skl 48hrs after AB Mx or til all the lesions are crusted/healed
what is erythrasma
asymptomatic, flat, slightly scaly, pink or brown rash usually found in the groin or axillae.
cause of erythrasma
overgrowth of the diphtheroid Corynebacterium minutissimum
examination of erythrasma
Wood’s light reveals a coral-red fluorescence.
management of erythrasma
Topical miconazole or antibacterial are usually effective. Oral erythromycin may be used for more extensive infection
causes of erythema nodosum
NO – idiopathic
D – drugs (penicillin sulphonamides)
O – oral contraceptive/pregnancy
S – sarcoidosis/TB
U – ulcerative colitis/Crohn’s disease/Behçet’s disease
M – microbiology (streptococcus, mycoplasma, EBV and more)
pathogen responsible for molluscum contagiosum
poxvirus
management for tinea pedis
Management includes general measures (drying of feet, avoiding occlusive footwear etc), topical antifungals - imidazole, undecenoate - 4 weeks
oral terbinafine and oral antifungals if unsuccessful
Ix for pityriasis versicolor
Woods light yellow green fluorescence
features of iron deficinecy anaemia
Pallor
Other signs: koilonychia, atrophic glossitis, post-cricoid webs, angular stomatitis
polycythaemia features
Pruritus particularly after warm bath
‘Ruddy complexion’
Gout
Peptic ulcer disease
CKD features
Lethargy & pallor
Oedema & weight gain
Hypertension
lymphoma features
Night sweats
Lymphadenopathy
Splenomegaly, hepatomegaly
Fatigue
liver disease features
History of alcohol excess
Stigmata of chronic liver disease: spider naevi, bruising, palmar erythema, gynaecomastia etc
Evidence of decompensation: ascites, jaundice, encephalopathy
tests for suspecting impetigo
swabs for microbiology
risk of prolonged use of ABx in impetigo
which bacterial toxin is implicted in impetigo
staph aureus has shown to develop AB resistance particularly to fusidic acid if it is used for linger than 2 wekks
staph aureus
Group A strep
if impetigo treatment fail intially
check swab and see if it sensitive to given AB
why may there be recurrent cases of impetigo in family
nasal carriage of staph aureus is quite common - not eradicated by oral or topical treatment
eraducated by use of antibacterial nasak ointment and antiseptic skin washes
what is erythrasma
generally asymptomatic, flat, slightly scaly, pink or brown rash usually found in the groin or axillae. It is caused by an overgrowth of the diphtheroid Corynebacterium minutissimum
examination of erythrasma
woods light coral red fluorescence
Mx for erythrasma
Topical miconazole or antibacterial are usually effective. Oral erythromycin may be used for more extensive infection
description of staphylococcal scalded skin syndrome
● Commonly seen in infancy and early childhood
causes of staphylocco
● Production of a circulating epidermolytic toxin from phage group
II, benzylpenicillin-resistant (coagulase positive) staphylococci
RFs of erysipelas
- previous episode
- breaks in the skin barrier
current/prior injury - exposure of umbilical cord and vaccination injury
- nasopharyngeal infection
- venous disease
- immune deficiency
— diabetes
— alcoholism
— obesity
— HIV - nephrotic syndrome
- pregnancy
causes of erysipelas
Strep pyogenes - group A beta haemolytic streptococci
staph aureus
MRSA
Mx of erysipelas
- cold packs and analgesics to relieve local discomfort
- elevation of an infected limb
- compression stockings
- wound care
ABx
- oral/IV pencillin
Mx of recurrent cellulitis
- Avoid trauma, wear long sleeves and pants in high-risk activities, such as gardening
- Keep skin clean and well moisturised, with nails well tended
- Avoid having blood tests taken from the affected limb
- Treat fungal infections of hands and feet early
- Keep swollen limbs elevated during rest periods to aid lymphatic circulation. Those with chronic lymphoedema may benefit from compression garments.
what is scabies
caused by mite sarcoptes scabiei - spread by prolonged skin contact
pathophysiology of scabies
mite burrows into the skin, laying its eggs in the stratum corneum
intense pruritis ass w scabies is due to a delayed type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection
features of scabies
- widespread pruritus
- linear burrows on the side of fingers, interdigital webs and flexor aspects of the wrist
- in infants the face, scalp may also be affected
- 2 Features - scratching: excoriation, infection
Mx of scabies and what do u tell the family
FIRST LINE - premethrin 5%
SECOND LINE - malathion 0.5%
- pruritus persists up to 4- 6 weeks post eradication
- avoid close physical contact with others until treatment is complete
- all household and close physical contacts should be treated at the same time, even if asymptomatic
- kill off mites with high heat
what is crusted scabies (Norwegian)
Mx
crusted scabies in pts with suppressed immunity esp HIV
Ivermectin
causes of onychomycosis
- dermatophytes - - Trichophyton rubrum
yeasts - candida - non-dermatophyte moulds
RFs for fungal nail infections
diabetes mellitus
increasing age
DD for onychomycosis
psoriasis
repeated trauma
lichen planus
yellow nail syndrome
Ix of onychomycosis
nail clippings
scrapings of the affected nail
Mx of onychomycosis
Diagnosis should be confirmed before starting treatment
Dermatophyte
- oral terbinafine FIRST LINE
6 weeks to 3 months therapy
Candida
- topical antifungals
really severe ORAL ITRACONAZOLE period of 12 weeks
topical Tx upto 6 months for fingernails and 9-12 months for toenails
what is hidradenitis suppurativa
characterisitcs
suspected in who
chronic, painful, inflammatory skin disorder.
characterised by the development of inflammatory nodules, pustules, sinus tracts and scars in intertriginous areas.
suspected in pubertal or post-pubertal patients who have a diagnosis of recurrent furnucles or boild
epidemiology and pathogenesis of hidradenitis suppurativa
epi
- women are more likely to devleop HS than men
- under 40
path
- chronic inflam occlusion of folliculopilosebaceous units that obstructs the apocrine glands and prevents keratinocytes from propely shedding from the follicular epithelium
RFs of hidradenitis suppurativa
FH
smoking
obesity, diabetes, PCOS
mechanical stretching of skin
clinical features of hidradenitis suppurativa
- > Initial manifestation involves recurrent, painful, and inflamed nodules.
- > HS occurs most commonly on intertriginous skin. However, non-intertriginous skin involvement also can occur. The axilla is the most common site
- > Other areas include inguinal, inner thighs, perineal and perianal, inframammary skin.
- > The nodules may rupture, discharging purulent, malodorous material.
- > Coalescence of nodules can result in plaques, sinus tracts and ‘rope-like’ scarring.
Mx of hidradenitis supparativa
- Encourage good hygiene and loose-fitting clothing
- Smoking cessation
- Weight loss in obese
- Acute flares can be treated with steroids (intra-lesional or oral) or flucloxacillin. Surgical incision and drainage may be needed in some cases.
- Long-term disease can be treated with topical (clindamycin) or oral (lymecycline or clindamycin and rifampicin) antibiotics.
- Lumps that persist despite prolonged medical treatment are excised surgically.
complications of hidradenitis supparativa
- Sinus tracts, fistulas
- Comedones
- Scarring - severe scarring can lead to dense, rope-like bands in the skin with strictures and lymphedema
- Contractures
- Lymphatic obstruction
DDx of hidradenitis supparativa
- Acne vulgaris - It primarily occurs on the face, upper chest, and back, whereas HS primarily involves intertriginous areas.
- Follicular pyodermas (folliculitis, furuncles, carbuncles) - Unlike HS, follicular pyodermas are transient and respond rapidly to antibiotics
- Granuloma inguinale (donovanosis) - It is a sexually transmitted infection caused by Klebsiella granulomatis. Suspect donovanosis if there is an enlarging ulcer that bleeds in the inguinal area.
features of seborrhoeic dermatitis
ass
nflammatory reaction related to a proliferation of a normal skin inhabitant, a fungus called Malassezia furfur
eczematous lesions on the sebum-rich areas: scalp (may cause dandruff), periorbital, auricular and nasolabial folds
otitis externa and blepharitis may develop
HIV
parkinson
scalp - T-gel - zinc pyrithione
ketoconazole
selenium sulphide and topical corticosteroid may also be useful
Face and body management
topical antifungals: e.g. ketoconazole
topical steroids: best used for short periods
difficult to treat - recurrences are common
mosaic warts
It is a cluster of viral warts sometimes several cm in diameter
Topical salicyclic preparations after soaking and rubbing away hard skin (may work better if covered by tape overnight). Treatment takes a long time and perseverance is essential. Repeated liquid nitrogen application may be required and will be difficult on an extensive area. Formalin soaks several times per week can be used. Other specialist treatment can include bleomycin intralesional injections. It is reasonable to do nothing as most warts eventually disappear spontaneously
