CN4 Scabies Flashcards
Serpiginous; linear track which is a few mm long and slightly black dot visible on one end
Burrow
Where are scabies burrows commonly located?
Fingers, palms, and around the wrist
What is the etiologic agent of scabies?
Mite Sarcoptes scabies var. hominis
How long are adult mites?
0.3-0.4mm long
Measures 0.4mm in length
Has four sets of legs
Has a hemispheric body mark by transverse corrugation,
brown spines and a vessel on the dorsal surface
Female adult mite
Life cycle of scabies
Mating –> gravid female burrow into the most superficial layer –> lays eggs 1-3/day –> larva hatches 3-5 days before leaving the burrow –> nymph molts in 4-6 mos –> mature in abt 2-3 wks
Especially in children
Chronic skin condition characterized by eczematous, itchy, honey crusted, scaled plaques
Atopic/Seborrheic dermatitis
Lichenification in flexural areas in children and adult
Atopic/Seborrheic dermatitis
Common afflictions in children characterized by persistent papules and are often excoriated and crusted accompanied by pruritus
Arthropod bites
Common afflictions in children characterized by persistent papules and are often excoriated and crusted accompanied by pruritus
Arthropod bites
Considered particularly in the crusted variety
Psoriasis
Common skin condition in which hair follicles become inflamed. It’s usually caused by a bacterial or fungal infection. At first it may look like small red bumps or white-headed pimples around hair follicles
Folliculitis
What does the first sign of infestation consists of?
• 1-2 mm red papules
- some are excoriated, crusted, or scaly
A latent period of how many months follows an initial infestation?
1 month
On reinfection, reaction to mic antigens are noted within how many hours?
1 hr
Intermittent that worsens after bathing or undressing and in bed at night
Severe pruritus
What are the classic lesion but may not be seen in infants?
Threadlike burrows
In ink burrow test a drop of what on a lesion should be placed
Mineral oil
When gently scraping away epidermis beneath it, what blade should you use?
No. 15 blade
Positive Ink burrow test
(+) mite, scybala (mite feces), or ova under LPO
Can the mite still be transmitted after 24 hours post-treatment?
Unlikely
What complications of untreated scabies may lead to?
Eczematous dermatitis Impetigo ecthyma Folliculitis Furunculosis Cellulitis Lymphangitis Id reaction/autoeczematization Streptococcal glomerulonephritis
Drugs that are used against parasites in human beings
Pediculocides and miticides
What is the best known anti ectoparasitic medication?
Lindane (Gamma benzene hexachloride; Kwell; Scabene)
The mixture lindane is applied in a thin layer over the entire cotton surface (from the neck down 30 grams cream for an adult) and is not removed for how many hours?
8-12 hrs
Why can’t lindane be used for pregnant, nursing women, and infants?
Neurotoxic effect (rare)
What is slightly more effective scabicide than lindane but is more expensive?
Permethrin 5% cream (Acticin; Elimite)
What is a better alternative for infants?
Permethrin 5% cream (Acticin; Elimite)
What is poorly absorbed, rapidly metabolized by tissue esterases therefore very low toxicity?
Permethrin 5% cream (Acticin; Elimite)
What is an alternative therapy for infants younger than two months, pregnant and nursing women?
6-10% Precipitated Sulfur
What is applied nightly for three nights from neck to toes?
6-10% Precipitated Sulfur
Messy, malodorous, stains clothing and commonly causes irritant dermatitis
6-10% Precipitated Sulfur
What is not recommended because of lack of efficiency but it is available for topical application 10% cream?
Crotamiton (N-ethyl-o-croronotoluidide; Eurax)
This is applied five successive nights and washed of 24 hours after last use
Paradoxically the preparation also has anti pruritic properties
Crotamiton (N-ethyl-o-croronotoluidide; Eurax)
Untoward effects include occasional irritation especially on inflamed skin or when applied over a long period of time; can also cause sensitization
Crotamiton (N-ethyl-o-croronotoluidide; Eurax)
Untoward effects include occasional irritation especially on inflamed skin or when applied over a long period of time; can also cause sensitization
Crotamiton (N-ethyl-o-croronotoluidide; Eurax)
What is used in dermatology to treat pruritus?
Oral antihistamines
In oral antihistamine what does not cause edition and are as effective as the older h1 blockers?
Newer h1 receptor blockers (second generation)
What are highly selective h1 receptors that are Piperidines (prototype: Terfenadine) H1 antagonists of this class (2nd generation) include
Terfenadine (Seldane)
Astemizole (Hismanal)
Loratidine (Claritin)
What does the drug do to your body AKA pharmacodynamics? Pipedrines
H1 antagonists suppress the itchiness caused by the release of histamine
What does the body do to the drug AKA pharmacokinetics? Pipedrines
- rapidly absorbed from the GI tract and metabolized in the liver to active metabolized by hepatic microsomal P450 system
- peak plasma concentration achieved in 2-3 hours
- effects lasts 4-6 hrs
- cannot cross the BBB
What are the untoward effects of piperidines?
- CNS: dizziness, tinnitus, lassitude, fatigue, incoordination, blurred vision, diplopia, euphoria, nervousness, tremors, and insomnia
- GI tract: loss of appetite, nausea, vomiting, epigastric distress, and constipation or diarrhea
What is an active metabolite of hydroxyzine and acrivastine?
Piperazine (Cetirizine hydrochloride)
What is well absorbed from the gastrointestinal tract but primarily excreted renal e in the unmetabolized form?
Piperazine (Cetirizine hydrochloride)
What may alleviate pruritus dt hypersensitivity to mite antigens which may persist for a number of days?
Topical glucocorticoids
What may be used to relieve pain and itching due to insect bites, minor cuts and burns, and to resolve rashes due to an allergy?
Topical antihistamines
Scabies causes a diffuse, pruritic eruption after an incubation pd of how many weeks?
4-6 weeks
pearl-like, translucent,
white, eyeless, and oval in shape with four pairs
of short stubby legs. The adult female mite is 0.4 ×
0.3 mm with the male being slightly smaller—just
slightly too small to be seen by the naked eye
scabies
The scabies mite is able to live for __ days away from the host
in a sterile test tube, and for __ days if placed in mineral
oil mounts.
3 days away fr host;
7 days in mineral oil mounts
What is the definitice diagnosis of scabies?
microscopic identi”cation of the scabies mites, eggs, or fecal pellets
(scybala)
Pathognomonic lesion
Burrow
DDx of Scabies
Most Likely
Atopic dermatitis
Dyshidrotic eczema
Pyoderma
Contact dermatitis
Insect bite reaction
Consider
Dermatitis herpetiformis
Psoriasis
Bullous pemphigoid
Drug eruption
Systemic causes of pruritus
Delusions of parasitosis
scabies infestation can also trigger
bullous pemphigoid
Oral antihistamines
- Piperadine (Terfenadine, Astemizole, Loratidine) Terfe & Astemizole not recommended bcs potentially fatal - alternative: Fexofonadine
- Piperazine
Erythematous, scaling, papules and plaques
Psoriasis
Marked thickening, NONpurritic and crusting of the skin
?????
Folliculitis etiology
S. aureus
Etiology of Seborrheic dematitis
Malassezia furfur
Well-demarcated red plaques w white scaly surfaces and bleeding points localized on elbows and knees
Psoriasis
