Skin infection

Question 1

What are the names for infections in various parts of the skin?

Answer 1

Impetigo – Infection of subcorneal layer of epidermis
Folliculitis – Infection of mouth of hair follicle
Ecythma – Infection of full thickness of epidermis
Boil – Abscess of hair follicle
Carbuncle – Abscess of several adjacent hair follicles

Question 2

Describe Staph Aureus infection

Answer 2

Is a gram +Ve bacterium
Produces toxins
Commensal bacteria (30% of the population carry it, either in the nostrils or on the skin)
Causes skin infections
Can be MRSA
Can cause infection of bones, joints, and lungs (particularly after influenza) and gives rise to SEPSIS

Question 3

What toxins can Staph Aureus release?

Answer 3

Panton Valentine Leucodine toxin (virulence factor)
PVL leads to necrotising infection (VERY SERIOUS)

EXFOLIATIVE toxin – cleavage of epidermis blistering

TSST-1 toxin – sickness, fever, malaise. → organ failure
50% of infections with staphylococcus aureus that produce TSST-1 toxin are related to tampons

ENTEROTOXIN – this is a problem in food consumption

Question 4

Describe Staph Aureus Impetigo

Answer 4

Impetigo from staph infection on epidermis surface

Has honey-coloured crust on eroded base

Mostly around the nose/mouth, can occur anywhere (particularly groin/perineal region)

Bullous impetigo can exist, in which the bacteria is making the exfoliative toxin. Toxin cleaves of the epidermis → extensive blistering. Blisters fairly superficial, easily broken and cause erosions

Question 5

What is Staph aureus scaled skin syndrome

Answer 5

CAUSE = SA exfoliative toxin enters blood affecting the skin, distant to the origin of the infection → cleavage of epidermis + Desquamation of the epidermis

SYSTEMIC. (Only epithelium) Commonly occurs in children under 5 (immature immune system)

TREAT WITH ANTIBIOTICS and EMOLLIENTS

Recovery takes place in a few days

Question 6

What may staph aureus scalded skin syndrome be mistaken for?

Answer 6

TOXIC EPIDERMAL NECROLYSIS: widespread desquamation of the skin, as a result of an allergic reaction to a drug.

In TEN, the mucous membranes ARE affected (mouth, eyes and genital areas along with the skin). Staph scalded skin syndrome ONLY affects the skin.

Question 7

What causes syphilis?

Answer 7

Treponema Pallidum

Question 8

What are the phases of syphilis?

Answer 8

Primary (at 3-8 weeks): Painless ulcer at inoculation site (Genital or oral)

Secondary (at 6-12 weeks): Disseminated infection, and generalised rash and lymphadenopathy

Tertiary syphilis (usually years later): Skin, neurological and vascular manifestations (e.g thoracic aneurysm)

Tertiary is rare, will only occur if secondary wasn’t treated. Time between phases is asymptomatic

Question 9

What is congenital syphilis?

Answer 9

Babies have been born to mothers infected with syphilis (trans-placental)
Most result in miscarriage or stillbirth
Babies born alive have features similar to secondary syphilis: rashes
Others asymptomatic but later develop tertiary syphilis symptoms

Question 10

How is syphilis treated?

Answer 10

Easily treated - easy to test for in serology and responds to penicillin

Question 11

What are the herpes family of viruses?

Answer 11

HHV1 - HHV8 (All show latency)

Question 12

What are HHV-1 and HHV-2?

Answer 12

Herpes Simplex Virus types 1 and 2 -
oro-genital herpes
Target: muco-epithelial
latency: neurones

Question 13

What is HHV-3?

Answer 13

Varicella zoster virus -
Chicken pox and shingles
Target: muco-epithelial
latency: neurones

Question 14

What is HHV-4?

Answer 14

Epstein–Barr virus -
infectious mononucleosis
Target: B cells
latency: B cells

Question 15

What is HHV-5?

Answer 15

Cytomegalovirus -
infectious mononucleosis like syndrome, retinitis
Target: Monocyte, epithelial cell
latency: lymphocytes

Question 16

What is HHV-6?

Answer 16

Roseola virus -
Roseola
Target: Lymphocytes
latency: lymphocytes

Question 17

What is HHV-7?

Answer 17

HHV-7 -
Pityriasis rosea
Target: T cell
Latency: Lymphocytes

Question 18

What is HHV-8?

Answer 18

Kaposi Sarcoma associated Herpes virus -
Kaposi Sarcoma
Target: Lymphocytes
Latency: B cells

Question 19

What can the presentation of herpes simplex cause?

Answer 19

stomatitis - severe inflammation of mouth and lips

Question 20

What is eczema herpeticum?

Answer 20

Severe HSV infection due to eczema

Patients need intravenous antibiotics, intravenous acyclovir, emollients and topical steroids

Question 21

Describe HHV-3 latency

Answer 21

The virus enters a period of dormancy, and lives in the dorsal root ganglions of the associated sensory
cutaneous nerves. It can reactivate – causing shingles (herpes zoster infection). This can be bullous – may blister. Patients may suffer from post-herpetic neuralgia

Question 22

What are Dermatophytes?

Answer 22

Dermatophytes are infecting moulds E.g. Trichophyton rubrum

Dermatophytes live off and grow in keratin (a protein that is part of the skin, hair and nails)
Long hyphae, grow from tip
Dermatophytes cause tinea – this is suffixed by the name of the body part
For example, tinea unguium – a dermatophyte infection of a nail

Question 23

Describe Tinea unguium

Answer 23

Tinea unguium often presents as a yellow, crumbly nail. It is often pigmented. To confirm that this is a dermatophyte infection, clippings of the nails can be
taken and sent away for culture. This takes 4-6 weeks. The patient needs a 3- month course of anti-fungal tablets – a cream would not work (the creams
cannot penetrate deep enough into the nail matrix).

Question 24

Describe Tinea Capitis

Answer 24

Dermatophyte infection of the scalp only occurs in children (adults have antifungal chemicals in the sebum of their hair, whereas children do not). This can
be diffuse or localised (kerion).

Some scrapings of the lesion can be cultured for diagnosis of the type of fungus. Patients are given anti-fungals orally (lesion is too deep for topical treatment).

Question 25

What is Tinea Manuum?

Answer 25

The other name for this is ringworm. We may also see tinea pedis (on the feet) and tinea cruris (affecting the skin of the groin region). Tinea facei is fungal infection of the face (this can occur if the patient has been cuddling an animal). Many dermatophytes are human to human, but CAN BE animal to human

Question 26

What is candida intertrigo?

Answer 26

Seen in the mouth, genital area, under the breast and in the axilla. This is an inflammatory candida yeast infection. Can be treated with a topical anti-fungal.

Question 27

Describe Sarcoptes scabei infection.

Answer 27

Scabies is a human to human disease (spread between humans by direct, skin to skin contact)
Should be treated topically and often clothes and bedding are washed at over 55 degrees

The mites and eggs cannot survive off the patient for very long. Transmission is commonly human to human (except in crusted scabies)

Crusted scabies: the patient is immunosuppressed, and has THOUSANDS of mites on the skin
The female mite burrows just under the stratum corneum (surface of the epidermis)

Question 28

Describe the presentation of scabies

Answer 28

For the first 4 weeks, the patient is asymptomatic. They then develop a type IV hypersensitivity reaction (allergic reaction) to the mite and its faeces. Then, they develop a very itchy, exematous rash (this keeps them awake at night). At this stage, they have BURROWS and a WIDESPREAD RASH.

Question 29

Where are scabies burrows found on the body?

Answer 29

Axilla, groin, wrist, dorsal hand, cubital fossa, Band across umbilicus