Skin and Soft Tissue Pathology Flashcards Preview

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Flashcards in Skin and Soft Tissue Pathology Deck (54):
1

4 commensal skin flora

Coagulase -ve staphylococci
Staph A
Proprionibacterium-acne
Corynebacterium

2

5 common commensal skin viruses

Herpes viruses (HSV, VZV)
Moluscum contagiosum
HPV
Orf
Cowpox

3

Which virus is transmitted from sheep and results in ulcerative skin lesions

Orf

4

HZV pathogenesis

Vesicle forms which grows to form an ulcer. When it ruptures, it releases vesicle fluid containing infectious particles. Virus gains entry via sensory nerve endings and migrates along the nerve to the DRG where it remains latent and the immune response is not stimulated. When reactivated, the virus migrates outwards to sensory nerve endings and causes the clinical manifestations of infection- preceded by tingling

5

Triggers of reactivation of HSV

Infection or stress

6

Primary infections of HSV

Extensive, painful lesion, occurs only once. Rare. Normally HSV1. HSV2 is usually genital herpes.

7

Secondary infections fo HSV

All ages, recurrent infection. Peri-oral. Weeping, vesicular

8

Diagnosis of HSV

Clinical
Vesicle fluid contains virus-PCR

9

Treatment for HSV

Cold sores- topical aciclovir
Genical herpes/immunocompromised- oral aciclovir

10

Another name for strep pyogenes

Beta haemolytic streptococci

11

Usual causative organisms for bacterial skin infections

Staph A
Strep P
H. Influenzae
Pasteurella mulficida (grow in cat and dog's mouths)

12

Gram +ve cocci in clusters. Catalase +ve. Normal nasal flora in 30% population

Staph A

13

Name some virulence factors of Staph A

DNAase
Coagulase
Teichoic acid
Exotoxin production e.g. epidemolytic toxins A & B, toxic shock syndrome toxin, PVL-boils

14

Really nasty bacteria, gram +ve cocci in chains. Catalase -ve.

Strep Pyogenes

15

Name some virulence factors of strep P

Adhesins
M. proteins (antiphagocytic)
Streptolysins O and S
Hyaluronic capsule (antiphagocytic)
Hyaluronidase (facilitates intestinal spread)
C5a peptidase (anticomplementary)

16

Describe the rash in VZV

Weepeing, vesicular rash

17

Treatment for VZV

Oral aciclovir//valaciclovir
IV aciclovir if older, lower immune system or increased susceptibility to shingles

18

Causative organism for molluscum contagiosum

Molluscum contagiosum virus-poxvirus

19

Describe the appearance of molluscum contagiosum

Raised pearly lesions, umbilicated (central depressions) No sequelae.

20

Treatment of molluscum contagiosum

None. Usually disappear within 6-18 months. Physical treatments some times appropriate if disfiguring.

21

Causative organism for Impetigo

S. Aureus/S.Pyogenes

22

Often occurs at site of skin damage, superficial, thick scabs-'honey crusted lesions', with yellow exudate. often around the nose.

Impetigo

23

Local manifestation of impetigo

Bullous impetigo

24

Generalised manifestation of impetigo

Staph scalded skin syndrome

25

Pathogenesis of impetigo

Desmosermal glycoprotein desmoglein-1 which is requied for cell to cell adhesion in the superficial epidermis is inactivated by ETA and ETB (epidermolytic toxin)

26

Causative organism for erysipelas

S. pyogenes

27

Erysipelas

Infection of dermis
Ocurs at site of skin damag, often face or shin. Preceded by pain and tenderness, well demarcated inflamed lesions-red, swollen, painful or hot. Fever, malaise and local lyphadenopathy.

28

Cellulitis

Infection of skin and subcutanous tissues, not bilateral.

29

Causative organisms of cellulitis

S. aureus
S. pyogenes
Pasteurella multicida (animal bites)
H. influenza

30

What bacteria might give rise to peri-orbital cellulitis?

H. influenza

31

Causative organism for anthrax

Bacillus anthracis-spore forming aerobic gram +ve bacillus, acquired from imported animal hides or wool.

32

Describe the skin lesions in anthrax

Malignant pustular-eschar- dry dark scab
may develop into septicaemia

33

Risk factors for anthrax

Drum skin exposure
Injecting drug users

34

Describe the different types of anthrax

Cutaneous anthrax-readily treated
Inhalation/septicaemic antrhax-high mortality

35

Necrotising fasciitis

Infection of the skin and SC tissue. Spontaneous or at site of skin penetration. Any part of the body. Dark, rapidly spreading, necrotic lesion. Fever and malaise.

36

Describe the 2 types of Necrotising fasciitis

Type 1: polymicrobial - enteric gram -ve bacilli and anaerobes i.e. normal bowel flora.
Type 2: strep pyogenes- acquired.

37

Another word for perineal necrotising fasciitis

Fournier's or syndergistic gangrene

38

Diagnosis of necrotising fasciitis

Blood or debrided material

39

Treatment for necrotising fasciitis

IV-antibiotics
or surgical debridement

40

Anaerobic Infections

Uncommon-ready availibility of O2.
Gas gangrene- similar to NF but with a palpable SC gas. Usually post operative at the site of surgery.

41

Common causative organism of gas gangrene

Clostridium perfringens

42

Treatment of gas gangrene

IV antibiotics
Surgical debridement

43

Treatment for impetigo (causative organism staph A)

Fusidic acid or mopirocen

44

Empiric bacterial skin infection treatment for those with a penicillin allergy

Erythromycin/clarithromycin/vancomycin/linezolid

45

Treatment for NF

Need to cover anaerobic bacteria so meropenem and clindamycin. Metronidazole is an anti-anaerobic agent.

46

Dermatophyte

Superficial fungal infection

47

Skin fungal infection

Tinea corporis, tinea pedis (athlete's foot)

48

Nail fungal infections

Onychomycosis

49

Scalp infections

Tinea capitis (scalp ringworm)

50

Describe Pityriasis Versicolour

What I have on my back- hypopigmented patches that come out in the summer- fungal infection

51

Causative organsims for dermatophyte infections

Tricophytum e.g T. rubum- circulates among humans
Microsporum- e.g. M.canis- circulates among animals

52

What level of the skin do you usually get dermatophyte infections?

Usually restricted to stratum corneum- rarely penetrate the lining cells of the epidermis. Use keratin as a nutritional substrate

53

Topical antifungal therapy

Clotrimazole
Terbinafine

54

Scalp and nale infections- systemic antifungal therapy

Terbinafine, itraconazole, friseofluin