Skin Infections

Question 1

erythema ill-defined on right leg on the tibial aspect

Answer 1

cellulitis

affects subcutaneous layer of the dermis

Group A ß - hemolytic streptococcus (Strep)

or Staph

Other if immunocompromised = Gram -ve rods, fungal

find site of entry (e.g. gardening, cut leg, shaving leg)

check webs of feet (e.g. athletes foot)

Question 2

Cellulitis Risk Factors

Answer 2

Diabetic

Alcohol

IVDU

eczema

malignancy

venous stasis

PVD

Systemic steroids

biologics

immunosuppressed

Question 3

Ix for cellulitis

Answer 3

Skin swab = negative, except children H. Influenza

Bloods = often only slightly raised inflammatory markers

Blood cultures = negative

Question 4

Cellulitis mx

Answer 4

Demarcation

Elevation

Dressings may be needed

Abx = flucloxacillin, benzylpenicillin

Question 5

Cellulitis complications

Answer 5

Recurrent lymphedema

Group a strep = glomerulonephritis

Bacterial endocarditis = ?metallic valve

Question 6

Answer 6

Lipodermatosclerosis = affects both legs (brown deposits on left leg)

Venous insufficiency

cellulitis?

unitlateral or bilateral?

acute or chronic?

Question 7

Lipodermatosclerosis mechanism

Answer 7

Venous hypertension, fibrin and vascular cuffing, ischaemic fat necrosis → fibrosis, haemosiderin deposit in the skin

tx = venous system

Question 8

cellulitis vs lipodermatosclerosis

Answer 8

Question 9

What is this?

Answer 9

onset of minutes , colour, pain, haemorrhage, bullae, raised CK

NECROTISING FASCIITIS

flesh eating bacteria

emergency

ix = CK, XR (osteomyelitis)

tx = debridement, get surgeons involved

Question 10

Unilateral

Answer 10

Erysipelas = unilateral

caused by strep pyogenes in upper subcutaneous fat

Question 11

Cellulitis vs erysipelas

Answer 11

Question 12

4 month history of rash

face only

scale

Answer 12

seborrhoea dermattits

M. Furfur

symmetrical, sebum areas, HIV if severe?

tx = azole antifungals, maintenance, steroids

Question 13

Answer 13

impetigo

fast spread, honeycomb crusting appearance, face and hands, initially vesicular, no prodrome unlike with HSV

staph infection

tx = none, topical, systemic if widespread

Question 14

blistering conditions

Answer 14

erythema multiform = target pattern

Question 15

what is this?

Answer 15

cold sore = HSV

prodrome, site, recurrence

recurrence = skin immunosuppression (UV radiation), stress, fever, common cold, altered immune states, altered hormonal milieu (menstruation)

Question 16

Answer 16

eczema herpeticum

hx of cold sores, medical emergency, well-punched out lesions all over face and may get around the body

get ophthalmology review as can get herpes keratitis

Question 17

HSV tx

Answer 17

systemic = aciclovir (oral/IV), IV for eczema herpeticum

Question 18

HSV and VZV

Answer 18

stored in dorsal root ganglion

shingles can affect trunk as well (reaction of VZV, prodrome)

Question 19

what is this?

Answer 19

pityriasis versicolor

Malasezzia furfur

predisposing factors = high humidity, high rate of sebum production

clinical diagnosis

Question 20

ringworm

Answer 20

Question 21

Answer 21

ix = skin swab

tx = anti-staph topical or systemic, antibacterial wash, eradicate nasal carriage if recurrent

Question 22

candidiasis thrush

Answer 22

direct microscopy = hyphae

fungal cultures

dermatopathology = PAS stains

Question 23

Answer 23

scabies

transmission = close prolonged contact

incubation = 2 to 6 weeks

rash usually in flexor areas

tx = lyclear (permethrin), derbac (malathion), wash all bedding and clothes (>50 degrees), treat all close family members