Skin Infections

Question 1

What determines whether a skin infection occurs or not? (3)

Answer 1

Virulence of organism
Ability of skin to resist
Host response

Question 2

What types of infections are there? (6)

Answer 2

Bacterial, viral, yeasts and fungi, mycobacterial, treponemal, parasites

Question 3

How does the epidermis act as a barrier?

Answer 3

1. Physical barrier (it is dry, and it also desquamates)
2. Chemical barrier (hostile to pathogens due to unsaturated fatty acids)
3. Bacterial inference (colonised by non-pathogenic skin flora to prevent other organisms from thriving)

Question 4

Give three examples of pathogens that make up normal skin flora.

Answer 4

Staphylococcus (in 20% of us)
Yeast (in 80% of us)
HPV (in 100% of us)

Question 5

Give examples of bacterial infections talked about in the lecture. (6)

Answer 5

Overgrowth of staphylococcus in eczema patient
Folliculitis
Impetigo
Cellulitis
Scolded skin syndrome/toxic shock
Necrotising fasciitis

Question 6

Describe overgrowth of staphylococcus in an eczema patient (impetiginisation).

Answer 6

Honey crusting
Widespread
Makes eczema worse and more oozy

Question 7

What is impetigo? How is it treated?

Answer 7

Inflammatory reaction, most commonly caused by staphylococcus. It is unusual in young, healthy people.
Topical antibiotics

Question 8

What does impetigo look like?

Answer 8

Golden crusting
Redness, blistering
Localised to small area

Question 9

What causes cellulitis? How is it treated?

Answer 9

Minor abrasions that don’t heal properly and so bacteria get in and spreads
Oral antibiotics

Question 10

What is scolded skin syndrome?

Answer 10

Staphylococcus infection in neonates – the bacteria has ingressed somewhere and is now elaborating a toxin that cleaves the skin.

Question 11

What is necrotising fasciitis?

Answer 11

A medical emergency – “flesh-eating disease”, i.e. necrosis of skin and elaboration of a toxin (toxin is what is killing the patient).

Question 12

What viral skin infections are mentioned in this lecture? (5)

Answer 12

Viral warts (commonly due to HPV)
Chicken pox (varicella)
Shingles
Herpes simplex
Molloscum contagiosum

Question 13

Which of these viral infections are common in children but NOT common in adults, so are therefore a cause for concern? (2)

Answer 13

Viral warts (may be due to AIDs, medications, or a haematological malignancy)
Molloscum contagiosum (again may be due to AIDs)

Question 14

What virus is shingles caused by? What is interesting about the distribution?

Answer 14

Same as chicken pox (varicella zoster)

Dermatomal

Question 15

How is shingles treated?

Answer 15

Acyclovir

Question 16

What yeast infections are mentioned in this lecture? (3)

Answer 16

Candida
Pityriasis versicolour
Tinea (and tinea incognito)

Question 17

What does Pityriasis Versicolor look like?

Answer 17

Brown scaly macules, mainly on the trunk. The affected areas do not tan in the sun so you can see a mottled appearance after sun exposure.

Question 18

What does tinea look like? What about tinea incognito?

Answer 18

A red ring
Tinea incognito (where you have fed the yeast, i.e. with steroid cream and it gets worse) is more widespread. Not really a circle anymore.

Question 19

What is Norwegian scabies?

Answer 19

Scabies (parasite) in an immune compromised patient

Question 20

Name some unusual skin infections. (5)

Answer 20

Cutaneous TB (lupus vulgaris)
Scrofuloderma (TB) – systemic disease, breakdown of lymph nodes.
Leprosy - due to mycobacterium
Leishmaniasis - acute red nodule, due to parasite.
Erythema chronicum migrans - due to tick bites. Big red rings. Can lead on to severe arthritis in later life if not treated.