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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
Q

When does secondary syphilis occur?

A

~50 days after chancre

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26
Q

How does secondary syphilis present?

A
  • Malaise
  • Fever
  • Headache
  • Pruritus
  • Loss of appetite
  • Iritis
  • ‘Great mimicker’
    • Rash
    • Alopecia
    • Mucous patches
    • Lymphadenopathy
    • Residual primary chancre
    • Condylomata lata
    • Hepatosplenomegaly
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29
Q

What is Lue maligna and how does it present?

A
  • Rare manifestation of secondary syphilis
  • Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
  • More frequent in HIV manifestation
30
Q

How does tertiary syphilis present?

A
  • 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
Q

How is syphilis diagnosed?

A
  • Clinical findings
  • Serology
  • Strong index of suspicion required in secondary syphilis
32
Q

What is the treatment for syphilis?

A

IM benzylpenicillin or oral tetracycline

33
Q

What is Herpes Simplex Virus and where does it occur?

A

Primary and recurrent vesicular eruptions

Favour orolabial and genital regions

34
Q

How does HSV transmission occur?

A
  • 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
Q

When do symptoms arise in HSV and what are they preceded by?

A
  • Symptoms within 3-7 days of exposure
  • Preceded by tender lymphadenopathy, malaise, anorexia +/- burning, tingling
36
Q

What are the symptoms of HSV infection?

A
  • 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
Q

What is eczema herpeticum?

A
  • Emergency
  • Monomorphic, punched out erosions (excoriated vesicles)
38
Q

What is Herpetic Whitlow?

A
  • HSV (1>2) infection of digits – pain, swelling and vesicles (vesicles may appear later)
  • Misdiagnosed as paronychia or dactylitis
  • Often in children
39
Q

How does neonatal HSV infection occur?

A
  • 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
Q

Where does neonatal HSV infection affect?

A
  • Localised usually – scalp or trunk
  • Vesicles → **bullae erosions **
  • Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits
41
Q

What does neonatal HSV infection require?

A

IV antivirals

42
Q

Who does severe/chronic HSV affect?

A

Immunocompromised patients

43
Q

What are the presentations of severe/chronic HSV?

A
  • 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
Q

How is HSV diagnosed?

A

Swab for polymerase chain reaction

45
Q

What is the treatment for HSV?

A

Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection

IV 10mg/kg TDS for 7-19days

46
Q

Where do fungal infections usually occur?

A
  • Superficial
  • Deep/soft tissue
  • Disseminated
47
Q

What is pityriasis versicolor?

A

Hypopigmented, hyperpigmented or erythematous macular eruption +/- fine scale

48
Q

What is pityriasis versicolor caused by?

A

Malassezia spp.

49
Q

When does pityriasis versicolor occur?

A
  • Begins during adolescence when sebaceous glands become active
  • Flares when temperatures and humidity are high (immunosuppression)
50
Q

What is given for pityriasis versicolor?

A

Topical azole

51
Q

What are dermatophytes?

A

Fungi that live on keratin

52
Q

What causes the most fungal infections?

A

Trichophyton rubrum

53
Q

What causes the most tinea capitis?

A

Trichophyton tonsurans

54
Q

What is kerion?

A

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
Q

What are Id reactions?

A

aka Dermatophytid reactions

  • Inflammatory reactions at sites distant from the associated dermatophyte infection
  • May include urticaria (hives), hand dermatitis, or erythema nodosum
56
Q

What causes Id reactions?

A

Likely secondary to a strong host immunologic response against fungal antigens

57
Q

What is candidiases caused by?

A

Candida albicans

58
Q

What is candidiases predisposed by?

A

Occlusion, moisture, warm temperature, diabetes mellitus

59
Q

How does candidiases present?

A
  • Most sites show erythema oedema, thin purulent discharge
  • Usually an intertriginous infection (skin folds) or of oral mucosa
  • Can become systemic (immunocompromise)
60
Q

What is candidiases a common cause of?

A

Vulvovaginitis

61
Q

What are the presentations of mucormycosis?

A

Oedema, then pain, then eschar
- Fever
- Headache proptosis
- Facial pain
- Orbital cellulitis +/- cranial nerve dysfunction

62
Q

What causes mucormyosis?

A
  • Apophysomyces
  • Mucor
  • Rhizopus
  • Absidia
  • Rhizomucor
63
Q

What are opportunistic fungal infections associated with?

A
  • Diabetes mellitus
  • Malnutrition
  • Uraemia
  • Neutropaenia
  • Medications: steroids/antibiotics/desferoxamine
  • Burns
  • HIV
64
Q

What is the treatment for mucormycosis?

A

Aggressive debridement and antifungal therapy amphoteracin

65
Q

What is scabies and what is it caused by?

A

Contagious infestation caused by Sarcoptes species.

Female mates, burrows into upper epidermis, lays her eggs and dies after one month

66
Q

What are the presentations of scabies?

A
  • 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
Q

What is the treatment for scabies?

A

Permethrin, oral ivermectin
- Two cycles of treatment are required

derm (3 decks)

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