Dermatologic Infections and Infestations

Question 1

Whats the most common superficial bacterial infection in kids? What agents cause this?

Answer 1

Impetigo

streptococci
Staphylococcus aureus

Question 2

What are the two kinds of impetigo and which bacteria usually cause them?

Answer 2

Non-bullous (70-80% of impetigos)

• impetigo contagiosa is usually streptococcal infections
• staph is most common cause of both

Bullous: staph

Question 3

How does non-bullous impetigo usually present in the clinic?

Answer 3

primary lesion with a “honey-colored” yellow crust on the face (nose of adults)

Skin to skin contact

Question 4

What causes bullous impetigo?

Answer 4

Staph makes toxin that affects desmosones of keratinocytes, making blisters all over the skin with layer of pus

Question 5

Who is susceptible to cellulitis?

Answer 5

– Very young
– Elderly
– Immunocompromised
– Intravenous drug users
– Patients with chronic ulcers

Question 6

What do you call the variant of cellulitis that is confined to the face? How does it present?

Answer 6

Erysipelas (St. Anthony’s fire)

-erythema that is well demarcated (cliff-drop border), with regional lymphadenopathy, Incubation period- 2 to 5 days

Question 7

What bacteria are most associated with cellulitis?

Answer 7

β-hemolytic streptococci (Streptococcus pyogenes), Staphylococcus aureus, and Haemophilus influenzae (in children)

Question 8

Where and how does cellulitis usually occur?

Answer 8

Usually in extremities from some trauma (ie: you cut your foot)

Question 9

What are common clinical presentations of cellulitis?

Answer 9

Primary lesion- tender ill-defined area of painful erythema with variable induration,
Lymphatic streaking- common
Lymphadenopathy- variable
Diagnose with CULTURE (more sensitive) on leading edge

Question 10

Where do you find dermatophytes and name the three kinds?

Answer 10

“they eat keratin”- nails, skin, hair

1. Epidermophyton
2. Microsporum
3. Trichophyton

Question 11

Which dermatophyte causes “socks and jocks” infections (athletes foot, jock itch)

Answer 11

epidermophyton

Question 12

Which dermatophyte gives tine corporis to kids from a cat

Answer 12

Microsporum

*also it flouresces

Question 13

Which dermatophyte is the most common to infect human?

Answer 13

Trichophyton

Question 14

Where does the term “ring-worm” come from?

Answer 14

Tinea (capitis, faciei, barbae, corporis, pedis)

- fungus that eats keratinocytes and spreads out in circle to make a ring-shaped plaque, alopecia, scaling in scalp

Question 15

What is “kerion” in relation to tinea?

Answer 15

It is an inflammatory response due to the fungus

Question 16

T/F: use topical steroids with fungus

Answer 16

False
You have to use systemic, because topical will suppress it locally and fungus will go deeper. Or topical fungicides- naftifine (think nasty-feet)

Question 17

What is candida?

Answer 17

A normal fluora of skin that can infect skin and mucous membranes in those with diabetes, occlusion, use of corticosteroids, or in patients treated with broad-
spectrum antibiotics

These eat glucose- not skin- so the infection is deeper

Question 18

List different candida infections

Answer 18

Thrush: white scaly stuff in mouth, common with HIV

Perleche: sores in corner of mouth

interdigitalis blastomycetica: white sores in between fingers

Candida diaper dermatitis: red rash on babies

Question 19

What causes tinea versicolor and who gets it?

Answer 19

Yeast (Pityrosporum orbiculare)

In post-puberty patients

Question 20

Clinical characteristics of tinea versicolor?

Answer 20

• Usually on trunk
• Primary lesion- asymptomatic, tan- colored subtly scaly macule or patch (scales from scratching)
• Hypopigmented variant
• “spaghetti and meatballs” under histology

Question 21

What are clinical characteristics of scabies? What causes it?

Answer 21

Sarcoptes scabiei parasite

• soft skin distribution
• itching- nocturnal accentuation
• Erythematous papules
• Erythematous burrows- variable scale

Question 22

What are clinical characteristics of lice?

Answer 22

• Head: Limited to scalp with the area behind the ears in the nape of the neck being the areas most commonly affected -Symptoms- intense pruritus (itch), Erythema, scale, and secondary infection commonly present
• Eggs attached to hair shafts or clothes if on body
• crab lice: genital area

Question 23

What is a Tzanck smear and what does it look for?

Answer 23

is scraping of an ulcer base to look for multinucelated keratinocytes and large vesicular nuclei in keratinocytes

Test for HSV (herpes)

Question 24

What does KOH prep look for?

Answer 24

scrape off border, dissolves epithelial cell and cell wall making it easier to identify differentiate Candida, dermatophyte, fungus, etc.

Question 25

What does a mineral oil (wet prep) look for?

Answer 25

Scabies

a small drop of mineral oil is placed on the skin in gently scraped and examined under a microscope for evidence of infestation (mites, eggs, or feces)

Question 26

What does a gram stain test for?

Answer 26

Impetigo & Cellulitis

sample of crust or fluid from intact bullae leading edge

Question 27

What does the Wood’s light exam do?

Answer 27

A Wood’s lamp examination is a procedure that uses transillumination (light) to detect bacterial or fungal skin infections- tinea capitis, tinea versicolor