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Dermatology > Lecture 5: Infestations > Flashcards

Lecture 5: Infestations Flashcards

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Dermatology Board Prep flashcards
1
Q

Where is pediculosis capitis MC and how does it present?

A
  • Lice
  • MC in schools, day-cares, SNFs, dorms, prisons
  • Intense pruiritis of the scalp
  • MC in white school aged girls/mothers

Warmer months

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2
Q

What does a louse look like?

A
  • 1-3 mm long, flattened brownish-gray, 3 pairs of legs and claws
  • lifespan 14-18d
  • Nits are 1 mm and opalescent (eggs)

Humanus are in clothing, capitus on hair shafts

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3
Q

How to differentiate seborrheic dermatitis, tinea capitis, psocid lice, and psoriasis from pediculosis capitis?

A
  • Seborrheic is yellow, greasy, and easy to remove
  • Tinea capitis is more closely associated with alopecia
  • Psocid lice are MC in plant debris/wooded areas
  • Psoriasis is morphologically distinct
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4
Q

What do lice and nits do to the scalp?

A
  • Mauculae cerulae or purpuritic stains may suggest infestation
  • Occipital lymph node involvement
  • Microscopy shows an oblong structure attached to hair an an acute angle with a breathing appartus at its superior end
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5
Q

Diagnostic pearls for pediculosis capitis

A
  • Pyoderma + occipital/cervical LAN suggest infestation
  • Nits are oval and tenacious; they stay stuck
  • Nits fluoresce under Wood’s lamp
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6
Q

Best tests for pediculosis capitis

A
  • Microscope
  • Wood’s lamp of nits
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7
Q

Management of pediculosis capitis

A
  • Permethrin has increasing resistance
  • Manual combing via fine comb
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8
Q

Should you treat a kid with empty nit cases?

A

No

Only live lice or eggs

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9
Q

OTC tx for pediculosis capitis

A
  • Permethrin (Nix): dry hair then rinse after 10m. Repeat in 1-2 weeks
  • Pyrethrins + piperonyl butoxide(RID, Pronto): same as above
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10
Q

Rx tx for pediculosis capitis

A
  • Spinosad/Natroba: children > 4y First line tx
  • Malathion lotion
  • Permethrin 5% (off-label)
  • Ivermectin lotion: 6 months or older & not preggo
  • Oral ivermectin (off-label), don’t use under 5y.
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11
Q

Tx for eyelid involvement of pediculosis capitis

A

Petrolatum BID for x8d

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12
Q

Organism for pediculosis corporis

A

Pediculus humanus corporis

Lives in clothing

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13
Q

Presentation of pediculosis corporis

A
  • Pruiritis
  • Bites of macules and papules in intertriginous areas
  • Maculae cerulea: blue gray macules are pathognomic for lice infestation
  • 2-4 mm wingless, blood sucking arthropods.
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14
Q

What is vagabond disease?

A

Body louse infection that goes on for years, developing parasitic melanoderma = darkened/thickened skin

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15
Q

What is characteristic of bed bug bites?

A

Linear bite distribution

Bfast, lunch, dinner distribution

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16
Q

Best test for pediculosis corporis

A
  • Physical examination
  • Finding a live louse/viable nit = confirmation of dx
  • Wood’s lamp will show yellow-green
  • Check clothing seams
  • Shake clothing and use tape to pick up debris
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17
Q

What are the 3 diseases transmitted by P. humanus corporis?

A
  • Typhus (Rickettsia prowazekii)
  • Relapsing fever (Borrelia recurrentis)
  • Trench fever (Bartonella quintana)

Mainstay is just eradicating infestation

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18
Q

Tx for pediculosis corporis

A
  • Clothing on hot water and high heat
  • Iron furniture
  • Heavy infestation: 5% permethrin cream or lotion for 8-14 hrs
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19
Q

Overview of pediculosis pubis

A
  • STD, aka crabs
  • Can be spread also by fomites
  • Not pet related
  • Extremely pruiritic
  • Condoms do not stop transmission
20
Q

Why is pediculosis pubis hard to remove?

A
  • Chitin formation to cement themselves.
  • However, can’t live without a host for more than 24h.
21
Q

Clinical signs of pediculosis pubis

A
  • Erythematous macules or papules present at feeding sites
  • Wheals
  • Small pinpoint bleeding on intimate clothing
22
Q

Management pearls for pediculosis pubis

A
  • Notify sexual partners in most recent month
  • Concomitant STDs is common
  • Sexual contact or fomite can be transmission
  • Wash in hot water or store away for 2 weeks in air-sealed bags
  • Secondarily infected lesions needs abx
23
Q

Preferred tx by CDC for pediculosis pubis

A
  • Permethrin 1% (> 2 month olds)
  • Mousse with pyrethrins
  • After tx, can remove nits with fine comb
24
Q

How does permethrin work?

A
  • Neurotoxin resulting in respiratory paralysis of parasite
  • Body: leave cream overnight and then rinse
  • Head lice: leave 10 mins, rinse and comb out.

Both are repeated in another week PRN.

25
Q

How does pyrethrin/piperonyl butoxide work and its CI?

A
  • Lotion/shampoo
  • Pyrethrin is a neurotoxin
  • Piperonyl is a synergist
  • Cannot be used in < 2 y/o or allergy to ragweed
  • Apply to wet areas for 10 mins and rinse.
26
Q

How does malathion work and its CI?

A
  • Head lice lotion that is Rx only
  • Neurotoxic: inhibits cholinesterase
  • CI: < 6y
  • Leave in dry hair for 8-12 hrs
  • It is flammable
27
Q

Last resort tx for pediculocide therapy

A

Lindane/Kwell

28
Q

What does Lindane do and CIs?

A
  • MOA: neurotoxicity causing seizure and death
  • BBW: neurotoxicity, so no children, elderly, light wt ppl
  • Banned in CA
  • Place on before you shower
  • Do not use more than once
29
Q

What causes scabies and MC mode of transmission?

A
  • Mite: Sarcoptes scabiei var. hominis
  • MC: Direct contact

fomite spread is rare

30
Q

Overview of scabies

A
  • 10-20 mites per infestation
  • Extremely pruiritic 2-6 weeks later
  • Persists without tx!
31
Q

Presentation of scabies

A
  • Worse at night
  • Diagnostic sign: fine, thread-like line with tiny black speck at the end.
  • Small, erythematous papules
  • Rarely on head or neck
32
Q

What location on men and women suggests scabies if itchy/papular?

A
  • Women: areola
  • Men: Penis and scrotum
33
Q

Dermoscopy finding for scabies

A

Jetliner with a trail

Negative prep != lack of scabies

34
Q

Who is crusted scabies/norwegian scabies MC in?

A
  • Immunocompromised
  • Institutionalized
35
Q

What is crusted scabies like?

A

Thousands to millions of mites

36
Q

Tx of crusted scabies

A
  • Topical Permethrin 5% overnight
  • +
  • Oral ivermectin x5 dosing
37
Q

Best tests for scabies

A
  • Scabies prep via scraping and microscopy and mineral oil
  • Add on KOH for crusted scabies
38
Q

Management of scabies

A
  • First-line: permethrin 5% or Rid
  • Last resort: Lindane (Avoid in crusted)
  • Oral ivermectin (2nd line, 0.2mg/kg/d)
39
Q

Supplies for skin scrapings

A
  • 15 scalpel blade
  • Microscope slide
  • Slide cover
  • Mineral oil or KOH
  • Microscope

KOH is for fungal or crusted

Mineral oil is applied prior to scraping for scabies.

40
Q

Overview of a black widow

A
  • MC widow spider
  • Likes woodpiles
  • Makes you extremely sick
  • Halo-like lesion around bite
  • Females have the red hourglass on their abd

Lactrodenus genus

41
Q

Overview of recluse spiders

A
  • MC in temperature and tropical regions
  • Cause local necrosis primarily
  • Loxosceles genus
  • Can cause DIC
  • Brown recluse spider has a violin shaped figure

Main concern is hemolysis i think

42
Q

Funnel-web spider overview

A
  • Hobo spider: tegenaria agrestis
  • PNW
  • Neurotoxic venom extremely fatal
43
Q

Overview of tarantulas

A
  • Theraphosphidae have relatively harmless bites
  • Generally cause local skin reactions/allergies
44
Q

How to find a spider bite

A
  • 2 small puncta fang marks
  • Erythema and edema
  • Necrotic/dusky center in a red inflammatory plaque
  • Brown recluse: vesicles and bullae quickly
  • Black widow: Local sweat, piloerection, mild edema
45
Q

Gold standard for diagnosing a spider bite

A

Spider collection with positive identification

46
Q

What should we check if we suspect brown recluse bite?

A
  • Hemolysis
  • Order Serial Hgb and plasma-free haptoglobin if hemolysis suspected.
  • Rhabdo, renal, DIC
47
Q

What controversial drug can we give for necrotic lesions due to spider bites within 36 hrs?

A

Dapsone

Dermatology (12 decks)

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