skin infections 2

Question 1

Impetigo

Answer 1

(crusted skin): Classic, nonbullous impetigo = impetigo contagiosa = epidemic
impetigo

Question 2

impetigo primarily caused by ??

Answer 2

S. aureus
Streptococcus pyogenes
(GAS) OR BOTH.

Question 3

classic impetigo epi:
age group??
how does it infect??
contagious or not??
what happens in adults??

Answer 3

Peak incidence is in children 2 to 5 years.

Often secondarily infect varicella lesions or lesions present in systemic diseases, such as diabetes mellitus and AIDS and causes scarring.

Contagious! Can be passed by fomites. Autoinoculation often causes spread to surrounding areas.

Adults more than children are at increased risk for complications, especially post-streptococcal acute glomerulonephritis (PGN-GAS)

Question 4

impetigo manifestation

Answer 4

In the superficial epidermis, purulent discharge drying on top of the lesion results in a thickened amber/honey colored adhesive crust that resolves in a couple of weeks without scarring.

Question 5

Common Factors Predisposing to Impetigo

Answer 5

Anything that causes scratching
Radiation therapy
Insect bites
Chicken pox
Scabies
Surgery
HSV
Thermal burns
Trauma
Acne

Question 6

epidemic impetigo secondary to ??

Answer 6

shingles: stops along midline
Ramsey-Hunt syndrome

“secondarily impetiginous”

Question 7

impetigo tx

Answer 7

Mupirocin: Impetigo involving limited areas: (topical) Unfortunately, S aureus and MRSA resistance to mupirocin

Retapamulin: New class of topicals/localized impetigo caused by S. pyogenes and MRSA
– Spectrum of retapamulin also includes erythromycin- resistant S. pyogenes, fusidic acid–resistant and mupirocin- resistant S. aureus, and MRSA (including P-VL–positive strains)
• Perform “D-zone test” on all erythromycin-resistant, clindamycin- sensitive strains to identify strains with inducible resistance to clindamycin

Question 8

if impetigo extends deeper??

Answer 8

ecthyma

Deep type of nonbullous impetigo extending into the dermis (“punched out ulcers” with a greenish-yellow crust and violaceous margin, often
suppurative)

Question 9

ecthyma mostly caused by ??

occurs where ??

Answer 9

More commonly caused by GAS (so worry about sequelae)
Frequently occurs on legs.
Scarring can occur.

Question 10

ecthyma dx

Answer 10

Gs/Cx to dx Staph from GAS

can also measure anti-teichoic acid Abs

Question 11

another FYI ecthyma

Answer 11

Ecthyma (Pyoderma) gangrenosum

most commonly caused by P. aeurginosa