Bugs, parasites, infections Flashcards
1
Q
What are possible reactions to arthropod bites?
A
excoriated pruritic papules, papular urticaria, pemphigoid vesicles and bullae, pseudolymphomatous nodules, anaphylaxis, secondary infections
2
Q
What are some diseases transmitted by fleas?
A
Rickettsia typhi, yersinia pestis
3
Q
What are some diseases transmitted by ticks?
A
Lyme disease, rocky mountain spotted fever, ehrlichiosis, anaplasmosis, tularemia
4
Q
What is the typical presentation of bedbug bites?
A
Erythematous pruritic nodules that often appear overnight in a linear or grouped arrangement (breakfast, lunch, and dinner bites)
5
Q
Where are bedbugs found?
A
Crevices of floors and walls, beddings, furniture (can survive for a long time without feeding)
6
Q
What is the vector for lyme disease?
A
Ixodes scapularis (deer tick)
7
Q
What are the three stages of lyme borreliosis?
A
Stage 1: localized
Stage 2: disseminated
Stage 3: persistent infection (months or years later)
8
Q
What is the classic presentation of lyme disease?
A
Erythema migrans with an initial erythematous macule/papule that enlarges within days to form an expanding annular lesion with a distinct red border and partially clearing center (bull’s eye)
9
Q
What organism causes scabies?
A
The mite sarcoptes scabiei
10
Q
How are scabies transmitted?
A
Skin to skin contact with another person with the parasitic infection
11
Q
What is the life cycle of the organism that causes scabies?
A
The female scabies mite burrows into the top layers of skin where she lays up to 3 eggs per day for one to two months
12
Q
What is the clinical presentation of scabies in immunocompetent patients?
A
Pruritic papules, usually somewhat scaly or crusted, preferentially distributed in “warm” areas of the body (axillae, groin, ankles, etc)
13
Q
What is the clinical presentation of scabies in immunocompromised patients?
A
“crusted” or norwegian scabies with thick scaly plaques over most of the body
14
Q
How is scabies diagnosed?
A
“scabies prep” - microscopic examination of skin scrapings that can reveal mites, eggs, or scybala (mite feces)
15
Q
What are different causes of pediculosis?
A
Pediculus humanis var. capitus (head), pediculus humanis var. humanus (body), pthirius pubis
16
Q
What is the transmission of pediculosis?
A
Direct contact between individuals or indirect contact with bedding, brushes, or clothing
17
Q
How is head lice identified?
A
Nits or organisms in hair
18
Q
What is the cause of tunga penetrans?
A
Sand flea infestation, classically along the toenail fold
19
Q
What is the appearance of lesions in tunga penetrans?
A
Papule or vesicle with central back dot (from the flea), can have intralesional hemorrhage, eggs/feces/flea organs are extruded when lesions are squeezed
20
Q
What locations are most likely sites for tunga penetrans lesions?
A
Feet, especially under toenails, between toes, and plantar aspects of feet
21
Q
What is the agent that causes cutaneous larva migrans?
A
Nematode parasites (a variety)
22
Q
What are the clinical manifestations of cutaneous larva migrans?
A
Erythematous, serpiginous, papular, or vesicular linear lesions
23
Q
What is the clinical presentation of myiasis?
A
A domed nodule that has a central pore through which the posterior end of botfly larva protrudes to respire
24
Q
A patient complains of itchy finger webs and on examination has scaling between the fingers, a few scaly papules on the wrists, and edematous pink papules and a few nodules on the scrotum. Next step:
a) recommend testing for STDs
b) skin scraping for KOH to evaluate for tinea manuum
c) skin scraping for scabies preparation
d) treatment for psoriasis
A
c) skin scraping for scabies preparation
scrotal nodules are scabies until proven otherwise
25
A patient was hiking in upstate New York 2 weeks ago and got many bug bites. One in the groin has not gone away but rather grown into a large annular plaque which she fears is ringworm. On examination she has a 7 cm pink annular nonscaly plaque in the inguinal area. She feels otherwise well. You suspect:
a) bedbug bites from her hotel
b) tinea cruris
c) erythema marginatum
d) erythema migrans
d) erythema migrans
## Footnote
*classic presentation of lyme borreliosis*
26
A patient presents with several linearly arranged pruritis edematous excoriated 5 mm papules on both of her legs. These seem to come in crops. It is winter and she has no known exposure to mosquitoes. Her husband may have had a few similar lesions. You recommend:
a) use of DEET when she goes outdoors
b) treatment for shingles
c) professional extermination
d) she should get a new mattress
c) professional extermination
## Footnote
*classic description for bedbugs, which requires extermination*
27
What is your diagnosis?
a) tinea versicolor
b) tinea corporis
c) tinea capitis
d) scabies
e) herpesvirus infection
b) tinea corporis
28
What is the most likely diagnosis?
Tinea corporis
29
What is the appearance of tinea corporis on KOH prep?
Fungi with hyphae that have septations
30
What is the most likely diagnosis?
Tinea corporis
31
What is the most likely diagnosis?
a) tinea versicolor
b) tinea corporis
c) tinea capitus
d) scabies
e) herpesvirus infection
c) tinea capitus
32
What is the histological presentation of tinea capitus?
Spores within and along hair shaft
33
What is the leading diagnosis?
Tinea capitus
34
What is the leading diagnosis?
a) tinea versicolor
b) tinea corporis
c) tinea capitus
d) scabies
e) herpesvirus infection
a) tinea versicolor
35
What is the appearance of tinea versicolor on histology?
Spaghetti and meatballs (yeast)
36
What is the most likely diagnosis?
Tinea versicolor
37
What is the most likely diagnosis?
Herpesvirus infection
38
What is the most likely diagnosis?
Scabies
39
What is the most likely diagnosis?
Scabies
40
What is the most likely etiology of scrotal nodules?
Scabies
41
What is the most likely diagnosis?
Scabies
42
What is the most likely diagnosis?
Norwegian scabies (scabies in immunocompromsied patients)
43
What organism is this? What disease might it transmit?
Louse - epidemic typhus
44
What disease might this transmit?
Lyme disease (deer tick)
45
What is the most likely diagnosis?
Lyme disease
46
What type of organism is this?
Bedbugs
47
What is the most likely diagnosis?
Bedbugs (breakfast, lunch, and dinner bites)
48
What is the most likely diagnosis?
Tunga penetrans/tungiasis
49
What is the most likely diagnosis?
Myiasis
50
What are the clinical presentations of tinea capitis?
Seborrheic (scaling with minimal inflammation), black dot (hair shaft is brittle and breaks at scalp), kerion (inflammatory, boggy plaque with broken hairs and oozing purulence)
51
What is the appearance of tinea capitis on Wood's lamp?
Green fluorescence in hair above level of scalp due to pteridines from infection
52
What types of infections cause tinea capitis?
Dermatophyte infection (microsporum, trichophyton, epidermophyton species)
53
How should tinea capitis be evaluated?
With a KOH prep of the hair and/or fungal culture
54
What is the treatment for tinea capitis?
Oral antimycotic agents and selenium sulfide or ketoconazole shampoo
55
What is the clinical presentation of tinea corporis?
Dermatophyte infections of glabrous skin, pruritic lesions with central clearing that resemble a ring ("ring worm"), centrifugal spread after 1-3 weeks incubation
56
What is the clinical presentation of tinea facei?
A form of tinea with facial involvement that excludes beard and moustache areas
57
What is the treatment for tinea corporis, cruris, facei, manuum, and pedis?
Topical or systemic -azole treatments
58
What is the most common cause of superficial and systemic candidiasis?
Candida albicans
59
What is the structure of candida albicans?
Yeast with pseudohyphae in the cold, germ tube formation in the warm
60
What is the clinical presentation of cutaneous candidiasis?
Erythematous, macerated areas of skin with satellite vesicopustules, which can break and leave scale
61
What is congenital candidiasis?
Candidiasis that is acquired in utero and presents within the first 24 hours of life as erythema and vesiculopustules with desquamation
62
What is neonatal candidiasis?
A form of candidiasis that is acquired at birth and develops several days after as erythema and satellite pustules that resemble intertriginous candidiasis
63
What is the treatment for cutaneous candidiasis?
Topical nystatin (localized), amphotericin B (systemic)
64
What is pityriasis versicolor?
A malassezia infection of the skin that causes fine, scaly/dustlike hypo-pigmented or salmon-colored patches on trunk and proximal extremities, more common in hot/humid weather
65
What is the finding of pityriasis versicolor on KOH prep?
Spaghetti and meatballs
66
Where are sporotrichosis infections most common?
Temperate and tropical countries, in US present in midwestern river valleys
67
What is the appearance of a sporotrichosis infection?
Dermal nodule that breaks down into a small ulcer, draining lymphatics that are inflamed and swollen, soft secondary nodules along the course of lymphatics
68
What is mycetoma?
A chronic localized infection caused by different species of fungi or actinomycetes, causes abscesses that can drain into sinuses or adjacent bones
69
Where are mycetoma infections most common?
Dry tropics with low annual rainfall
70
What is the clinical presentation of chromoblastomycosis?
Chronic fungal infection of the skin where pigmented fungi are implanted into the skin causing inflammation
71
Where is chromoblastomycosis most commonly found?
Mostly in tropical regions throughout central and south america
72
What are the main types of endemic respiratory mycoses?
Histoplasmosis, blastomycosis, coccidiodomycosis, paracoccidiodomycosis
73
What is the clinical presentation of systemic blastomycosis infection?
Lungs, skin, bones, CNS
74
What geographic regions have endemic blastomycosis?
North America (great lakes region and southern US) and Canada
75
What is the presentation of a skin lesion from disseminated blastomycosis?
Papule or nodule that may ulcerate and discharge pus
76
What is the presentation of blastomycosis on KOH prep?
Rounded, refractile spherical cells with broad-based buds
77
What is the most common cause of superficial pyodermas?
Staphylococcus aureus, group B strep (in babies)
78
What are superficial pyodermas?
Infections in the epidermis, just below the stratum corneum (impetigo) or hair follicles (foliculitis)
79
What is the clinical presentation of nonbullous impetigo?
Lesions that arise on the skin of the face (nares) or extremities after trauma. Initial lesion is a transient vescile or pustule that evolves into a honey-colored crust.
80
What is the clinical presentation of bullous impetigo?
A condition caused by staph aureus where exfoliative toxins cause blistering by binding to desmoglein-1, causing bullae with yellow fluid that rupture and form honey-colored crusts
81
What is the treatment for impetigo?
Bacterial culture to determine sensitivity. Treat with mupirocin ointment and oral antibiotic (specifically penicillin if group A strep)
82
What is folliculitis?
Multiple small papules and pustules on an erythematous base that are pierced by a central hair (although hair may not always be visible)
83
What is a furuncle?
Larger boil-like lesion that contains pus
84
What are common types of folliculitis?
Staph aureus (most common), gram negatives (enterobacter, klebsiella, escherichia, serratia, proteus), pseudomonal (hot tub folliculitis)
85
What is the main cause of erythrasma?
Corynebacterium minutissimum
86
What is erythrasma?
Chronic superficial infection of the intertriginous areas of skin with brownish/red patches with fine scales along skin folds
87
What factors predispose people to erythrasma?
Excessive sweating, delicate cutaneous barrier, obesity, DM2, warm climate, poor hygiene, advanced age
88
What is the treatment for erythrasma?
Topical erythromycin
89
What are the main causes of cellulitis?
Staph aureus/group a strep, MRSA
90
What is cellulitis?
Deep, local infection with red hot swollen tender skin
91
What is the treatment for cellulitis?
Systemic antibiotics
92
What is the cause of toxic shock syndrome?
TSST-1 superantigen from staph aureus
93
What is the cause of scalded skin syndrome?
Exfoliatin toxins A & B from staph aureus phage group 2 types 71 and 55
94
How do exotoxins from staph aureus cause scalded skin syndrome?
The toxins bind to desmoglein-1 in the granular cell layer
95
Who is most likely to experience scalded skins yndrome?
Patients \< 5 (due to decreased renal function)
96
What is the appearance of scalded skin syndrome?
Faint orange-red scarlitiniform eruption that become large, flaccid bullae. Begins with tissue paper-like wrinkling of epidermis followed by flaccid bullae in the axillae/groin that spreads over the body. The epidermis is then shed.
97
What is the treatment for scalded skin syndrome?
Antibiotics, supportive care, fluid/electrolyte management
98
What is the cause of scarlet fever
Streptococcal pyogenic exotoxins (SPE-A,B,C) from group A streptococcus in pharyngeal infection
99
What type of skin reaction is scarlet fever?
Delayed-type skin reactivity to strep products (requires prior exposure)
100
What are the constititutional symptoms of scarlet fever?
Pharyngitis, fever, headache, and chills with a rash after 1-2 days
101
What are the enanthematous symptoms of scarlet fever?
Beefy-red pharynx and tonsilitis with submandibular lymphadenopathy, strawberry tongue (white first, then red), petechiae of the soft palate
102
What are the exanthematous symptoms of scarlet fever?
First appears on the head/neck, spreads to whole body (except palms and soles) within 1-2 days, diffuse erythema with sandpaper quality, circumoral pallor, marked rash in skin folds, linear petechia in antecubital and axillary folds
103
What is the treatment for scarlet fever?
Penicillin
104
What is the cause of antrhax?
Bacillus anthracis (large, box-car shaped, gram-positive, non-motile, spore-forming rod)
105
What are the three presentations of anthrax?
Inhalational, GI, cutaneous
106
What is the appearance of cutaneous anthrax?
Painless papule that develops a central vesicle, ulcers, and forms a black eschar that can progress to bacteremia and death
107
What causes black eschar in anthrax?
Lethal factor and edema factor from bacillus anthracis
108
What is the presentation of pulmonary anthrax?
Flulike symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock
109
What is the cause of secondary syphilis?
Untreated infection with treponema pallidum
110
What is the clinical progression of syphilis?
Primary lesion: chancre (ulcer with raised borders and erythematous base)
Secondary: wide-spread papulosquamous skin lesions with diffuse scaly papules that can look like psoriasis and classically involve palms and soles with associated lymphadenopathy, "moth eaten" alopecia, and mucous patches
111
What is the immunopathogenesis of secondary syphilis?
T cell reaction in the lesions of secondary syphilis
112
What is the test for syphilis?
Serum RPR with prozone, treponemal tests
113
What is the treatment for syphilis?
Penicillin
114
What are the two most frequent skin forms of tuberculosis?
Lupus vulgaris and scrofuloderma
115
What is lupus vulgaris?
A progressive form of cutaneous tuberculosis with nodular skin lesions on the face
116
What is scrofuloderma?
Subcutaneous tuberculosis that leads to cold abscess formation and a breakdown of overlying skin that can be multibacillary or paucibacillary
117
What are the risk factors for mycobacterium marinum?
History of trauma and water, fish/seafood related hobbies and occupations
118
What is the presentation of mycobacterium marinum?
Violaceous papule at the site of trauma 2-3 weeks after inoculation that can lead to a nodule or psoriasiform or verrucous plaque that may ulcerate
119
What is leprosy?
A chronic granulomatous infection caused by mycobacterium leprae that primarily affects skin and nerves
120
How can the diagnosis of dermatophyte infection be confirmed?
a) Tzanck smear
b) KOH prep
c) mineral oil prep
d) punch biopsy
b) KOH prep
121
Whenever possible, bacterial infections should have what test performed in order to confirm the diagnosis and guide management?
a) gram stain
b) bacterial culture
c) bacterial culture and sensitivity
d) KOH prep
e) Tzanck smear
c) bacterial culture and sensitivity
122
What is the most likely diagnosis?
Tinea pedis
123
What is the most likely diagnosis?
Onychomycosis
124
What is the most likely diagnosis?
Tinea corporis
125
What is the most likely diagnosis?
Tinea versicolor
126
What is the most likely diagnosis?
Candidal intertrigo
127
What is the most likely diagnosis?
Sporotrichosis
128
What is the most likely diagnosis?
Blastomycosis
129
What is the most likely diagnosis?
Bullous impetigo
130
What is the most likely diagnosis?
Non-bullous impetigo
131
What is the most likely diagnosis?
Staphylococcal scalded skin syndrome
132
What is the most likely diagnosis?
Scarlet fever
133
What is the most likely diagnosis?
Cellulitis
134
What is the most likely definition?
Erysipelas
135
What is the most likely diagnosis?
Abscess
136
What is the most likely diagnosis?
Folliculitis
137
What is the msot likely diagnosis?
Furunculosis
138
What is the most likely diagnosis?
Carbunculosis
139
What is the most likely diagnosis?
Cutaneous anthrax
140
What is the most likely diagnosis (added HPI: lesions on palms and soles)?
Secondary syphilis
141
What is the most likely diagnosis?
Lupus vulgaris
142
What is the most likely diagnosis?
Scrofuloderma
143
What is the most likely cause of this lesion on a pet shop employee?
Mycobacterium marinum
144
What is the most likley diagnosis?
Mycobacterium leprae
145
