👍🏻Dermatology👍🏻- Infections & Infestations of Skin Flashcards
What is folliculitis?
Follicular erythema; sometimes pustular
May be infectious or non-infectious
What types of non-infectious folliculitis are there?
Eosinophilic (non-infectious) folliculitis is associated with HIV
What can cause recurrent folliculitis?
Recurrent cases may arise from nasal carriage of Staphylococcus aureus, particularly strains expressing Panton-Valentine leukocidin (PVL)
What is the treatment for folliculitis?
Antibiotics (usually flucloxacillin or erythromycin)
Incision and drainage is required for furunculosis
What is furunculosis?
Skin condition that causes painful boils, or furuncles, to develop on the body
What is the difference between a furuncle and a carbuncle?
A furuncle is a deep follicular abscess
Involvement with adjacent connected follicles = Carbuncle
Why are carbuncles more serious than furuncles?
Carbuncle more likely to lead to complications such as cellulitis and septicaemia
What can lead to infection by staph. aureus?
Establishment as a part of the resident microbial flora - abundant in nasal flora
Immune deficiency
- Hypogammaglobulinaemia
- Hyper-IgE syndrome – deficiency - Chronic granulomatous disease
- AIDS
- Diabetes Mellitus
What is Panton Valentine Leukocidin ?
Toxin produced by some strains of Staphylococcus aureus (S. aureus)
What effect panton valentine leukocidin produce?
β-pore-forming exotoxin
Leukocyte destruction and tissue necrosis
Higher morbidity, mortality and transmissibility
Skin
- Recurrent and painful abscesses
- Folliculitis
- Cellulitis
- Often painful, more than 1 site, recurrent, present in contacts
What are the extracutaneous effects of panton valentine leukocidin?
Necrotising pneumonia
Necrotising fasciitis
Purpura fulminans
What are the “risk of acquiring” 5 C’s?
Close Contact – e.g. hugging, contact sports
Contaminated items , e.g. gym equipment, towels or razors.
Crowding – crowded living conditions such as e.g. military accommodation, prisons and boarding schools.
Cleanliness (of environment)
Cuts and grazes – having a cut or graze will allow the bacteria to enter the body
How is a staph. aureus infection producing PVL treated?
Consult local microbiologist / guidelines
Antibiotics (often tetracycline)
Decolonisation – often:
- Chlorhexidine body wash for 7 days
- Nasal application of mupirocin ointment 5 days)
Treatment of close contacts
What is cellulitis?
Infection of lower dermis and subcutaneous tissue
Tender swelling with ill-defined, blanching erythema or oedema
What is the treatment for cellulitis?
Systemic Abx
What is a predisposing factor for cellulitis?
Oedema
What is impetigo?
Superficial bacterial infection, stuck-on, honey-coloured crusts overlying an erosion
Often affects face (perioral, ears, nares)
What causes impetigo?
Caused by:
- Streptococci (non-bullous)
or
- Staphylococci (bullous)
What is meant by bullous or non-bullous impetigo?
Bullous has boils, non-bullous is more common with a golden crust
What is the treatment for impetigo?
Topical +/- systemic antibiotics
What is impetiginisation?
Occurs in atopic dermatitis
- Gold crust
- Staphylococcus aureus
What is Borreliosis?
Lyme disease
Annular erythema develops at site of the bite of a Borrelia-infected tick
Initial cutaneous manifestation: Erythema migrans (only in 75%)
- Erythematous papule at the bite site
- Progression to annular erythema of >20cm
What is the progression of Borreliosis/Lyme disease?
1-30 days after infection, fever, headache
Multiple secondary lesions develop - similar but smaller to initial lesion
Neuroborreliosis
- Facial palsy / other CN palsies
- Aseptic meningitis
- Polyradiculitis
Arthritis – painful and swollen large joints (knee is the most affected join)
Carditis
What is the treatment for Lyme disease?
Doxycycline
Amoxicillin
Azithromycin
Why is Lyme disease/borreliosis quite difficult to treat?
Serology not sensitive
Histopathology - non-specific
High index of suspicion required for diagnosis
What is syphilis?
An STI
What occurs upon primary infection with syphilis?
Chancre -painless ulcer with a firm indurated border
Painless regional lymphadenopathy one week after the primary chancre
Chancre appears within 10-90 days
What is secondary syphilis?
Begins ~50 days after chancre
Malaise, fever, headache, pruritus, loss of appetite, iritis
Why is syphilis (particularly in later stages) quite difficult to diagnose?
Great mimicker’ – low threshold for testing - imitates many other conditions, has non-specific and systemic features
- Rash (88-100%) -Pityriasis rosea-like rash
- Alopecia (‘moth-eaten’)
- Mucous patches
- Lymphadenopathy
- Residual primary chancre
- Condylomata lata - wart like lesions
- Hepatosplenomegaly
What are common signs of syphilis?
Orogenital lesions
Can be misdiagnosed as HPV infection
What are Lues maligna?
Rare manifestation of secondary syphilis
Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
More frequent in HIV manifestation
What is tertiary syphilis?
Serious and potentially fatal stage of syphilis
Can occur years or even decades after initial infection
What is seen in tertiary syphillis?
Gumma skin lesions - nodules and plaques
Extend peripherally while central areas heal with scarring and atrophy
Mucosal lesions extend to and destroy the nasal cartilage
Cardiovascular disease
Neurosyphilis (general paresis or tabes dorsalis)
What is the treatment for syphilis?
IM benzylpenicillin or oral tetracycline
Outline HSV
Herpes simplex virus
HSV-1 – direct contact with contaminated saliva / other infected secretions
HSV-2 - sexual contact
Replicates at mucocutaneous site of infection
How does HSV cause neurological symptoms and meningitis?
Travels by retrograde axonal flow to dorsal root ganglia
What are the characteristic features of HSV?
Primary and recurrent vesicular eruptions
Favour orolabial and genital regions
Transmission can occur even during asymptomatic periods of viral shedding
How long do the symptoms take to arise in HSV?
Symptoms with 3-7 days of exposure
Preceded by tender lymphadenopathy, malaise, anorexia ± Burning, tingling
What are the systemic manifestations of HSV?
Aseptic meningitis in up to 10% of men
Outline the orogenital manifestations of HSV
Painful rouped vesicles on erythematous base → ulceration / pustules / erosions with scalloped border
Crusting and resolution within 2-6 weeks
Orolabial lesions – often asymptomatic
Genital involvement – often excruciatingly painful→ urinary retention
What is an emergency dermatological manifestation of HSV?
Eczema herpeticum
Monomorphic, punched out erosions (excoriated vesicles)
Typically background of poorly-controlled eczema
What is the treatment for Eczema herpeticum?
IV acyclovir and treatment of eczema
What is herpetic whitlow?
HSV (1>2) infection of digits – pain, swelling and vesicles (vesicles may appear later)
Misdiagnosed as paronychia or dactylitis
Often in children
How does neonatal HSV infection arise?
Exposure to HSV during vaginal delivery – risk higher when HSV acquired near time of delivery
HSV 1 or 2
Onset from birth to 2 weeks
How doe neonatal HSV present?
Vesicles → bullae erosions
Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits
Requires IV antivirals
Outline sever or chronic HSV
How is HSV diagnosed?
Swab of Polymerase chain reaction
How is HSV treated?
Don’t delay
Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection
Intravenous 10mg/kg TDS X 7-19 days
What is pityriasis versicolor?
Superficial fungal infection
Hypopigmented, hyperpigmented or erythematous macules +/- fine scale
Begins during adolescence (when sebaceous glands become active)
Flares when temperatures and humidity are high – e.g. in summer months
Topical azole
What are dermatophytes?
Fungi that live on keratin
What fungus causes the most infections?
Trichophyton rubrum
What is kerion?
an inflammatory fungal infection that may mimic a bacterial folliculitis or an abscess of the scalp; scalp is tender and patient usually has posterior cervical lymphadenopathy
What is candidiasis?
Commonly known as a yeast infection
Candida albicans
Most sites show erythema oedema, thin purulent discharge
Usually an intertriginous infection (skin folds) or of oral mucosa
A common cause of vulvovaginitis
Can become systemic (immunocompromise)
What can predispose candidiasis?
occlusion
moisture
warm temperature
diabetes mellitus
What is mucormycosis?
Opportunistic fungal infection
Oedema, then pain, then eschar
Can lead to - fever, headache proptosis, facial pain, orbital cellulitis +/- cranial nerve dysfunction
What are the associations of mucormycosis?
Diabetes mellitus (1/3 of patients - DKA very high risk
Malnutrition
Uraemia
Neutropaenia
Medications: Steroids / antibiotics / desferoxamine
Burns
HIV
What is the treatment for mucomycosis?
Aggressive debridement & antifungal therapy amphoteracin
What is scabies?
Contagious infestation caused by Sarcoptes species
Female mates, burrows into upper epidermis, lays her eggs and dies after one month
How does scabies appear?
Insidious onset of red to flesh-coloured pruritic papules
Affects interdigital areas of digits, volar wrists, axillary areas, genitalia
A diagnostic burrow consisting of fine white scale
Crusted or ‘Norwegian’ scabies - hyperkeratosis
- Often asymptomatic; immunocompromised individuals
What is the treatment of scabies?
Permethrin, oral ivermectin
- Two cycles of treatment are required
