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1B skin infections and infestations Flashcards

1
Q

What is folliculitis?

A

Inflammation or infection of a hair follicle or other sebaceous unit

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2
Q

How does folliculitis present and what can it be associated with?

A
  • Follicular erythema; sometimes pustular
  • May be infectious or non-infectious
  • Eosinophilic (non-infectious) is associated with HIV.
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3
Q

What can recurrent folliculitis arise from?

A

Nasal carriage of Staphylococcus aureus, particularly strains expressing Panton-Valentine leukocidin (PVL)

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4
Q

How is folliculitis treated?

A
  • Antibiotics (flucloxacillin or erythromycin)
  • Incision and drainage is required for furunculosis)
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5
Q

What is the difference between a furuncle and a carbuncle?

A
  • A furuncle is a deep follicular abscess
    • Involvement with adjacent connected follicles
      = Carbuncle.
  • Carbuncle - more likely to lead to complications such as cellulitis and septicaemia
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6
Q

Why might recurrent cases of folliculitis arise?

A
  • Establishment of Staph aureus as a part of the resident microbial flora
    • Abundant in nasal flora
  • Immune deficiency
    • Hypogammaglobulinaemia
    • HyperIgE syndrome – deficiency
    • Chronic granulomatous disease
    • AIDS
    • Diabetes Mellitus
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7
Q

What is PVL Staph Aureus and what does it do?

A

Panton Valentine Leukocidin Staphylococcus Aureua

  • β-pore-forming exotoxin
  • Leukocyte destruction and tissue necrosis
  • Leads to high morbidity, mortality and transmissibility
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8
Q

How does PVL staph aureus affect the skin?

A
  • Recurrent and painful abscess
  • Folliculitis
  • Cellulitis

Often painful, more than one site, recurrent, present in contacts

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9
Q

What extracutaneous presentations are there of PVL staph aureus infection?

A
  • Necrotising pneumonia
  • Necrotising fasciitis
  • Purpura fulminans
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10
Q

What are the risks of acquiring PVL Staph aureus?

A

5C’s

  • Close contact
  • Contaminated items
  • Crowding
  • Cleanliness
  • Cuts and grazes
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11
Q

What is the treatment of PVL Staph Aureus infection?

A
  • Consult local microbiolost/guidelines
  • Antibiotics (often tetracycline)
  • Decolonisation
    • Chlorhexidine body wash for 7 days
    • Nasal application of mupirocin ointment for 5 days
  • Treatment of close contacts
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12
Q

What is cellulitis and how does it present?

A
  • Infection of lower dermis and subcutaneous tissue
  • Tender swelling with ill-defined blanching erythema or oedema

Oedema is a predisposing factor

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13
Q

What is cellulitis most commonly caused by?

A

Streptococcus pyogenes and staphylococcus aureus

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14
Q

What is the treatment for cellulitis?

A

Systemic antibiotics

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15
Q

What is impetigo?

A

Superficial bacterial infection, stuck-on, honey-coloured crusts overlying an erosion.

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16
Q

What is impetigo caused by?

A

Caused by
- Streptococci (non-bullous)
or
- Staphylococci (bullous)

Caused by exfoliative toxins A & B, split epidermis by targeting desmoglein I.

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17
Q

Where does impetigo often affect?

A

Face (perioral, ears, nares)

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18
Q

How is impetigo treated?

A

Topical +/- systemic antibiotics

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19
Q

Where does impetiginisation occur and by what?

A

In atopic dermatitis
- Gold crust
- Staphylococcus aureus

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20
Q

What is borreliosis (lyme disease)?

A
  • Annular erythema develops at site of the bite of a Borrelia-infected tick
  • Bite from Ixodes tick infected with Borrelia burgdorferi
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21
Q

What are the initial cutaneous manifestations of borreliosis?

A

Erythema migrans (only in 75%)

  • Erythematous papule at the bite site
  • Progression to annular erythema of >20cm
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22
Q

How does borreliosis present?

A
  • 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
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23
Q

What investigations are done for borreliosis?

A
  • Serology not sensitive
  • Histopathology - non-specific
  • High index of suspicion required for diagnosis
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24
Q

What is syphilis and what does it cause?

A
  • Treponema pallidum
  • Primary infection Chancre -painless ulcer with a firm indurated border
  • Painless regional lymphadenopathy one week after the primary chancre
  • Chancre appears within 10-90 days
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25
When does secondary syphilis occur?
~50 days after chancre
26
How does secondary syphilis present?
- Malaise - Fever - Headache - Pruritus - Loss of appetite - Iritis - 'Great mimicker' - Rash - Alopecia - Mucous patches - Lymphadenopathy - Residual primary chancre - Condylomata lata - Hepatosplenomegaly
27
28
29
What is Lue maligna and how does it present?
- Rare manifestation of secondary syphilis - Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis - More frequent in HIV manifestation
30
How does tertiary syphilis present?
- 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 - CVD - Neurosyphilis (general paresis or tabes dorsalis)
31
How is syphilis diagnosed?
- Clinical findings - Serology - Strong index of suspicion required in secondary syphilis
32
What is the treatment for syphilis?
IM benzylpenicillin or oral tetracycline
33
What is Herpes Simplex Virus and where does it occur?
Primary and recurrent vesicular eruptions Favour orolabial and genital regions
34
How does HSV transmission occur?
- Transmission can occur even during asymptomatic periods of viral shedding - HSV-1 – direct contact with contaminated saliva / other infected secretions - HSV-2 - sexual contact Replicates at mucocutaneous site of infection - Travels by retrograde axonal flow to dorsal root ganglia
35
When do symptoms arise in HSV and what are they preceded by?
- Symptoms within 3-7 days of exposure - Preceded by **tender lymphadenopathy, malaise, anorexia +/- burning, tingling**
36
What are the symptoms of HSV infection?
- **Painful rouped vesicles** on erythematous base → ulceration / pustules / erosions with scalloped border - **Crusting and resolution** within 2-6 weeks - **Orolabial lesions** - **Genital involvement** – often excruciatingly painful→ urinary retention - **Systemic manifestations**– aseptic meningitis in up to 10% of omen - **Reactivation** – spontaneous, UV, fever, local tissue damage, stress
37
What is eczema herpeticum?
- Emergency - **Monomorphic, punched out erosions** (excoriated vesicles)
38
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
39
How does neonatal HSV infection occur?
- 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
40
Where does neonatal HSV infection affect?
- Localised usually – **scalp or trunk** - Vesicles → **bullae erosions ** - **Encephalitis** → mortality >50% without treatment, 15% with treatment → neurological deficits
41
What does neonatal HSV infection require?
IV antivirals
42
Who does severe/chronic HSV affect?
Immunocompromised patients
43
What are the presentations of severe/chronic HSV?
- Most common presentation – chronic, enlarging ulceration - Multiple sites or disseminated - Often atypical e.g. verrucous, exophytic or pustular lesions - Involvement of respiratory or GI tracts may occur
44
How is HSV diagnosed?
Swab for polymerase chain reaction
45
What is the treatment for HSV?
**Oral valacyclovir** or **acyclovir** 200mg five times daily in immunocompetent localised infection IV 10mg/kg TDS for 7-19days
46
Where do fungal infections usually occur?
- Superficial - Deep/soft tissue - Disseminated
47
What is pityriasis versicolor?
Hypopigmented, hyperpigmented or **erythematous macular eruption +/- fine scale**
48
What is pityriasis versicolor caused by?
Malassezia spp.
49
When does pityriasis versicolor occur?
- Begins during adolescence when sebaceous glands become active - Flares when temperatures and humidity are high (immunosuppression)
50
What is given for pityriasis versicolor?
Topical azole
51
What are dermatophytes?
Fungi that live on keratin
52
What causes the most fungal infections?
Trichophyton rubrum
53
What causes the most tinea capitis?
Trichophyton tonsurans
54
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**. Frequently secondarily infected with Staph aureus
55
What are Id reactions?
aka Dermatophytid reactions - **Inflammatory reactions** at sites distant from the associated dermatophyte infection - May include urticaria (hives), hand dermatitis, or erythema nodosum
56
What causes Id reactions?
Likely secondary to a strong host immunologic response against fungal antigens
57
What is candidiases caused by?
Candida albicans
58
What is candidiases predisposed by?
Occlusion, moisture, warm temperature, diabetes mellitus
59
How does candidiases present?
- Most sites show **erythema oedema**, thin purulent discharge - Usually an **intertriginous infection** (skin folds) or of **oral mucosa** - Can become systemic (immunocompromise)
60
What is candidiases a common cause of?
Vulvovaginitis
61
What are the presentations of mucormycosis?
Oedema, then pain, then eschar - Fever - Headache proptosis - Facial pain - Orbital cellulitis +/- cranial nerve dysfunction
62
What causes mucormyosis?
- Apophysomyces - Mucor - Rhizopus - Absidia - Rhizomucor
63
What are opportunistic fungal infections associated with?
- Diabetes mellitus - Malnutrition - Uraemia - Neutropaenia - Medications: steroids/antibiotics/desferoxamine - Burns - HIV
64
What is the treatment for mucormycosis?
**Aggressive debridement** and antifungal therapy **amphoteracin**
65
What is scabies and what is it caused by?
Contagious infestation caused by Sarcoptes species. Female mates, burrows into upper epidermis, lays her eggs and dies after one month
66
What are the presentations of scabies?
- 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
67
What is the treatment for scabies?
Permethrin, oral ivermectin - Two cycles of treatment are required

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