Peds - Derm

Question 1

Atopic derm pathophys

Answer 1

Rash due to defective skin barrier susceptible to drying, leading to pruritus & inflammation

Disruption of the skin barrier (filaggrin gene mutation) and disordered immune response which manifests mostly in infancy or almost always by age 5

Question 2

MC bug causing 2ndary infection in atopic derm

Answer 2

S. Aureus

Question 3

Contact derm pathophys

Answer 3

Inflammation of the dermis & epidermis from direct contact between a substance & the skin surface

Allergic: type IV hypersensitivity reaction (T cell lymphocyte-mediated), delayed by days

Irritant: non-immunologic reaction (immediate)

Question 4

Parkland formula to manage LR in burns

Answer 4

Parkland Formula to determine how much LR: 4mL x %BSA x weight (kg)

Question 5

MCC of perioral derm

Answer 5

MC in young woman w/ hx of prior topical steroid use in area

Question 6

Tx of perioral derm

Answer 6

Topical metronidazole; can also use erythromycin or Pimecrolimus

If no clearance: systemic tx w/ minocycline, doxycycline or tetracycline

Question 7

Morbilliform or maculopapular drug eruption characterized by macules/small papules after the initiation of drug treatment

Answer 7

Drug eruption

Type IV delayed hypersensitivity reaction that most commonly occurs 5-14 days after initiation of offending medication or within 1-2 days in previously sensitized individuals

Question 8

Self-limited localized subcutaneous (or submucosal) swelling resulting from extravasation of fluid into interstitium

Answer 8

Angioedema

Question 9

2 types of angioedema

Answer 9

Mast-cell (histamine) mediated – allergic reactions • Angioedema that may be accompanied w/ other allergic reaction symptoms (urticaria, flushing, generalized pruritus, bronchospasm, stridor, throat tightness, & hypotension)

Bradykinin-mediated: ACE inhibitor-induced or hereditary (d/t C1 esterase inhibitor deficiency) Angioedema without allergic reaction symptoms

Question 10

Tx of angioedema for mast cell mediated & bradykinin mediated

Answer 10

Mast-cell (histamine) mediated – epinephrine (if severe), glucocorticoids, and antihistamines

Bradykinin-mediated: • C1 inhibitor concentrate, Ecallantide (kallikrein inhibitor), Icatibant (bradykinin-beta2 receptor antagonist), FFP if other therapies aren’t available

Question 11

What type of reaction is erythema multiforme

Answer 11

Type IV hypersensitivity reaction assoc. w/ certain infections, medications (sulfa drugs), & other various triggers

Question 12

MC RF of erythema multiforme

Answer 12

MC: HSV, Mycoplasma in children, S. pneumoniae

Meds: sulfa drugs, beta-lactams, Phenytoin, Phenobarbital, Allopurinol

Malignancy, autoimmune, idiopathic

Question 13

Target lesions w/ 3 components on trunk & extremities: (1) dusky, central area or blister + (2) dark red inflammatory zone surrounded by pale ring of edema + (3) erythematous halo on extreme periphery of lesion

Answer 13

Erythema multiforme

Also (-) Niklosky skin

Question 14

Tx of erythema mutliforme

Answer 14

• Symptomatic: d/c offending drug, give antihistamines, analgesics, skin case
• Oral lesions: Corticosteroid + Lidocaine + Diphenhydramine mouthwash
• Severe: systemic corticosteroids
• Mycoplasma related: antibiotics • HSV related: Acyclovir

Question 15

S/S of dermatitis medicamentosa

Answer 15

Abrupt onset of eruption of widespread, symmetric, pruritic erythematous lesions w/ many types

• MC skin reaction to drugs: erythema
• Fever &/ other syx may be present – HA, malaise, arthralgias, &/or myalgias

Question 16

Difference in SJS vs TEN

Answer 16

SJS: sloughing involving <10% of body surface

TEN: >30% body surface area

Question 17

widespread flaccid bullae beginning on trunk & face before spreading to other areas (palms and soles rarely involved)

Pruritic targetoid lesions (erythematous macules w/ purpuric centers) or diffuse erythema w/ involvement of at least 1 mucous membrane + involvement with epidermal detachment (+ Nikolsky sign), skin often tender to touch

Answer 17

SJS or TEN

Question 18

Tx of SJS or TEN

Answer 18

Discontinue causative agent • Supportive: treat like severe burns – burn unit admission, pain control, prompt withdrawal of offending meds, fluid & electrolyte replacement, wound care w/ gauze and petroleum

Question 19

MC Bug in impetigo

Answer 19

MCC: S. auereus

2nd MCC: Group A Streptococcus

Question 20

Tx of i mpetigo

Answer 20

Mild: Mupirocin topically TID X10d, may use Bacitracin or Retapamulin; good skin hygiene, wash area with soap & water to prevent recurrence @ distant sites

Extensive disease or systemic syx: systemic antibiotics – Cephalexin or Dicloxacillin, Macrolides

Community acquired MRSA?: Doxycycline, Clindamycin, Bactrim or Linezolid PO x7days

Question 21

Head lice tx

Answer 21

Pediculus humanus capitis

Drug of choice: Permethrin topical, shampoo left x10min & use of a fine tooth cone to remove nits, reapply 7-10d

Alternative: Malathion – 8-12h tx period

*Oral Ivermectin in refractory cases

Question 22

Pediculus humanus corporis

Answer 22

Body lice

Sexually transmitted, strongly related to poor body hygiene; can be a vector for diseases to humans like relapsing fever, epidemic typhus, & trench fever

Question 23

Difference in body lice vs head/pubic lice

Answer 23

Body lice do not live on skin; they live & lay eggs in seams of clothing/bedding & move to skin only to feed

Question 24

Phthiriasis pubis tx

Answer 24

pubic lice

1st line: topical Permethrin or Pyrethrins x8-10 hours • Repeat tx if lice remains after 9-10 days • Treat sexual partners & launder clothing & bedding

Question 25

Multiple, small erythematous papules, excoriations Linear burrows (pathognomonic) – commonly found in intertriginous zones, including the scalp & web spaces between fingers & toes, spares neck and face

Answer 25

Scabies

Question 26

Tx of scabies

Answer 26

**Permethrin topical from neck down 8-14 hours before showering, repeat once after 1w \*\* Safe in pregnancy & lactation** May use Lindane – cheaper, can cause seizures d/t incr. absorption through open pores, DON’T USE IN PREGNANT PATIENTS Infants/pregnant woman: 6-10% sulfur in petroleum jelly **Extensive: Ivermectin**

Question 27

Dx of scabies

Answer 27

Clinical • Skin scrapings will show mites, eggs, & feces

Question 28

6 P’s: Purple. Polygonal, planar, pruritic, papules or plaques w/ irregular borders

Answer 28

Lichen planus

Question 29

Koebners phenomenon

Answer 29

Koebner’s phenomenon: new lesions at site of trauma [may see in psoriasis also]

Question 30

What is wickham striae in lichen planus

Answer 30

Wickham Striae: lacy striation [fine white lines] on lichen planus lesion or on oral mucosa

Question 31

Tx of lichen planus

Answer 31

**1st line: Topical steroid ointment • Antihistamines for pruritus** 2nd line: PO/intralesional CS, topical Tretinoin or photosensitizing Psoralen + UV light therapy General Measures: will resolve spontaneously in 8-12 months

Question 32

Etiology of tinea capitis

Answer 32

90% caused by Trichophyton tonsurans, 10% Microsporum

Question 33

Sx of tinea capitis

Answer 33

**Patches of alopecia w/ black dots:** multiple black dots are d/t broken hair shafts d/t endothrix infection **Scaly patches w/ alopecia:** single or multiple patches w/ hair loss, erythema & pruritus may be present **Kerion**: severe manifestation characterized by inflammatory plaque w/ pustules & thick crusting, often painful **Favus:** less common form – cup-like shaped yellow crusts composed of dried scalp secretions, fungi, skin cells & dead inflammatory cells

Question 34

Definitive dx of tinea capitis

Answer 34

**KOH Prep** – most common initial test, fungal element inside or surrounding the hair **Wood’s lamp:** no fluorescence w/ Trichophyton spp., (+) fluorescence with Microsporum **Definitive Diagnosis: Culture**

Question 35

Tx of tinea capitis

Answer 35

Oral Griseofulvin: first line treatment x6-12 weeks, can cause hepatitis, GI, headache, & Disulfiram rxn; better absorption w/ fatty food; may add topical 2.5% selenium sulfide/ketoconazole shampoo 2x/week to suppress spores 2nd line: Oral Terbinafine, less common: Itraconazole or Fluconazole

Question 36

most common dermatophyte infection

Answer 36

Tinea pedis - athlete's foot