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Project - USMLE Step 3 > Symptom To Diagnosis - Rash > Flashcards

Symptom To Diagnosis - Rash Flashcards

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USMLE® Step 1 flashcards
1
Q

12 morphologies of rash:

A
  1. Macule.
  2. Patch.
  3. Papule.
  4. Plaque.
  5. Nodule.
  6. Tumor.
  7. Cyst.
  8. Vesicle.
  9. Bulla.
  10. Pustule.
  11. Wheal.
  12. Comedone.
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2
Q

Macule:

A

Lesion without elevation or depression, <1cm.

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3
Q

Patch:

A

Lesion without elevation or depression, >1cm.

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4
Q

Papule:

A

Any solid, elevated “bump” <1cm.

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5
Q

Plaque:

A

Raised plateau-like lesion of variable size, no depth, often a confluence of papules.

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6
Q

Nodule:

A

Solid lesion with palpable elevation, 1-5cm.

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7
Q

Tumor:

A

Solid growth, >5cm.

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8
Q

Cyst:

A

Encapsulated lesion, filled with soft material.

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9
Q

Vesicle:

A

Elevated, fluid-filled blister <1cm.

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10
Q

Bulla:

A

Elevated, fluid-filled blister >1cm.

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11
Q

Pustule:

A

Elevated, pus-filled blister, any size.

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12
Q

Wheal:

A

Inflamed papule or plaque formed by transient and superficial local edema.

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13
Q

Comedone:

A

A plug of keratinous material and skin oils retained in a follicle, open is black, closed is white.

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14
Q

Acne vulgaris - Textbook presentation:

A

Presents in adolescence with chronic, waxing and waning lesions. A variety of lesions are present, including inflammatory papules, pustules, comedones, and nodulocysts over the face, chest, and back.

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15
Q

What is the main cause of acne?

A

Obstruction of sebaceous follicles on the face and trunk.

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16
Q

3 factors are involved in the development of acne lesions:

A
  1. Increased sebum production (androgen dependent) –> Obstructs the follicles.
  2. Excessive desquamation of epithelial cells and keratin into follicles –> Obstructs the follicles.
  3. Inflammation 2o to proliferation of the anaerobe Propionibacterium acnes.
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17
Q

Besides the main 3 factors - 4 other factors that may contribute to the disease?

A
  1. Hyperandrogen states –> PCOS or androgenic progestins in OCPs.
  2. Exposure to topical comedogens (cocoa butter, mineral oil, lanolin, fatty acids).
  3. Numerous factors that lead to follicular obstruction.
  4. Medications known to trigger or exacerbate acne –> Steroids, INH, Li, androgens.
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18
Q

EBD of acne:

A

Diagnosis is typically clinical.

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19
Q

EBD of acne - Histopathology:

A

Will vary depending on the lesion. Comedones have a distinctive histologic appearance.

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20
Q

EBD of acne - Work-up:

A

Work-up for hyperandrogenism is appropriate when there are signs of PCOS, virilization, or an atypical presentation (such as later in life).

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21
Q

Rosacea - Textbook presentation:

A
  1. Adults - Facial rash.
  2. Gradual development of telangiectasia and persistent centrofacial erythema occasionally with inflammatory red papules and papulopustules.
  3. Comedones are ABSENT.
  4. History of easy flushing.
  5. Rash may worsen with sun exposure, ingestion of spicy food and hot liquids, emotional stress, and exercise.
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22
Q

Rosacea - Description of lesion:

A
  1. Centrofacial persistent erythema.
  2. Telangiectasias.
  3. Inflammatory papules and papulopustules.
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23
Q

Rosacea - Epidemiology:

A
  1. MC in fair-skinned individuals of northern European descent.
  2. Can be seen in people with darker skin as well.
  3. Women > Men.
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24
Q

Rosacea epidemiology - Complicated disease with sebaceous gland hyperplasia and rhinophyma (sebaceous overgrowth causing deformity of the nose) develops more common in men or women?

A

Men.

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25
Q

Rosacea epidemiology - When does it begin?

A

Typically begins later than acne and reaches a peak in middle age - Possible overlapping.

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26
Q

EBD of rosacea:

A

Diagnosis is by clinical presentation.

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27
Q

EBD of rosacea - Histopath:

A

Varies according to the stage and variant of the disease and is often non specific.

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28
Q

VZV textbook presentation:

A

A rash over a single, unilateral dermatome.

  • -> Lesion begin as closely grouped vesicles on an erythematous base.
  • -> Over 2-3 days, the lesions become pustular and then crust over after 7-10days.
  • -> Pain and paresthesias along the involved dermatome often precede the rash by a few days.
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29
Q

VZV description of the lesion:

A

Small, tightly grouped vesicles on an erythematous base, occurring in one dermatome.
–> Very early –> Lesions are large papules and then become vesicular, then pustular, and ultimately crusted.

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30
Q

VZV - Rash tends to occur where?

A

In the region of the primary VZV infection (chickenpox) was most severe.

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31
Q

VZV - MC dermatomes are:

A
  1. Trigeminal.
  2. T3-L2.
    - -> Not uncommon to have a few vesicles in contiguous dermatomes.
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32
Q

VZV - New lesions may appear for?

A

Several days, occasionally for up to 7 days.

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33
Q

Shingles is caused by?

A

Reactivation of VZV in a dorsal root ganglion.

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34
Q

VZV complications - Herpes zoster ophthalmicus:

A
  1. Can occur when there is involvement of the V1.

2. HIGH RISK of corneal damage.

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35
Q

VZV complications - Ramsay-Hunt syndrome:

A
  1. Reactivation of VZV within the geniculate ganglion.
  2. Bell’s palsy (facial paralysis) + ear pain.
  3. Vesicles can often be seen in the ear canal.
  4. Vestibular and hearing disturbances (vertigo and hearing loss or tinnitus) are frequently reported.
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36
Q

EBD of shingles:

A

Clinically, without additional tests.

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37
Q

EBD of shingles - Detection of virus:

A
  1. Rapid by immunofluorescence.

2. Bedside Tzanck smear of material scraped from a fresh vesicle –> Cannot distinguish between VZV/HSV.

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38
Q

EBD of shingles - Gold standard:

A

Viral cultures.

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39
Q

Bullous impetigo - Textbook presentation:

A

Most commonly seen in children, bullous impetigo presents as flaccid, transparent bullae in the intertriginous areas. Blisters rupture easily and leave a rim of scale and a shallow moist erosion.

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40
Q

Bullous impetigo - Description of the lesion:

A

Flaccid bullae on normal skin.

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41
Q

Bullous impetigo - Location of the lesion:

A
  1. On grossly INTACT skin as a result of local toxin production.
  2. Lesions most commonly develop on moist, intertriginous skin.
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42
Q

Bullous impetigo - Causative agent:

A

S.aureus.

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43
Q

Bullous impetigo - Mechanism of lesion:

A

Blistering is caused by the production of exfoliatin or epidermolytic toxins.

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44
Q

EBD of bullous impetigo:

A
  1. Clinical diagnosis.

2. Culture of blister fluid or the moist edge of a crusted plaque may be diagnostic.

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45
Q

Bullous arthropod bites - Textbook presentation:

A

This condition commonly presents as a cluster of tense blisters on exposed skin.
–> Blisters tends to be large (>1cm) and surrounding skin is normal.

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46
Q

Bullous arthropod bites - Description of the lesion:

A

Large, often tense blisters on normal skin.

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47
Q

Bullous arthropod bites - Character and location of the lesion:

A
  1. Lesions tend to develop in exposed areas of the skin, such as the extremities.
  2. Patient will otherwise appear well.
  3. Lesions are typically extraordinarily pruritic.
  4. Although the blisters arise from otherwise normal skin, surrounding inflammatory changes from rubbing and scratching are often present.
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48
Q

What are basically arthropod bite reactions?

A

Dermal HSR to antigens in the saliva of insects.

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49
Q

Common arthropod culprits?

A

Fleas and bedbugs.

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50
Q

EBD of bullous arthropod bites:

A
  1. Clinical diagnosis.

2. Histopath is supportive –> Edema, subepidermal blister, dermal inflammation with EOSINOPHILS.

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51
Q

Bullous pemphigoid - Textbook presentation:

A

Usually seen in elderly patients with the sudden onset of 1-2cm tense blisters and bright red, urticarial plaques.
–> Lesions often begin on the lower extremities and progress upward.

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52
Q

Bullous pemphigoid - Description of lesion:

A

Tense bullae arising on skin that may be normal, erythematous, or urticarial.

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53
Q

Bullous pemphigoid - Autoantibodies:

A

Components of the epidermal BM zone, thus triggering separation and blistering.

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54
Q

Bullous pemphigoid - Lesion heal?

A

Heal without scarring.

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55
Q

Bullous pemphigoid - Character and location of the lesion:

A
  1. Predilection of blisters for the extremities.
  2. Lesions range from asymptomatic to intensely pruritic.
  3. Mucosal surfaces are rarely involved.
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56
Q

EBD of bullous pemphigoid - Histopath:

A

Supportive information, demonstrating a subepidermal blister plane and accumulation of EOSINOPHILS.

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57
Q

EBD of bullous pemphigoid - Immunopath:

A

Confirms diagnosis by demonstrating linear deposits of IgG and C3 at the DERMAL-EPIDERMAL junction.

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58
Q

EBD of bullous pemphigoid - Circulating IgG?

A

In 70-80% of patients, circulating IgG that recognizes the identified antigens of the BM zone can be found.

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59
Q

Stevens-Johnson syndrome (SJS) - Textbook presentation:

A

Typically presents in a patient with fever, malaise, headache, and myalgias who is taking a potentially causative medication.

  • -> After 1 week of symptoms –> MACULAR RASH develops on the CHEST + FACE.
  • -> Lesions subsequently blister and then rapidly erode.
  • -> Skin is excruciatingly tender!
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60
Q

SJS - Description of the lesion:

A
  1. Flaccid bullae and vesicles that develop centrally within pre-existing target lesion.
  2. Bullae rapidly erode, leaving red and raw skin.
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61
Q

SJS and toxic epidermal necrolysis?

A

HSR patterns involving the skin.
2 conditions often considered to be on a spectrum of severity.
SJS –> Less body surface area.
TEN –> Leads to considerable areas of full-thickness skin sloughing.

62
Q

More than … drugs have been implicated as causes of SJS and TEN.

A

200

63
Q

SJS course - Prodromal symptoms:

A

Fever, malaise, headache, myalgias, as well as GI and respiratory complaints, occur over 1-2weeks.

64
Q

SJS course - Rash occur initially?

A

On the FACE and CENTRAL TRUNK as pink to red macules and papules.

65
Q

SJS course - Rash may spread:

A

Spread and evolve rapidly, with individual lesions becoming targetoid with dusky centers and ultimately coalescing into larger plaques.

66
Q

SJS course - Flaccid bullae and vesicles?

A

May develop centrally within targets as the skin necroses.

67
Q

SJS course - Blisters?

A

Blisters form and rapidly erode, leaving red and raw skin that becomes coated by a gray-white pseudomembrane.

68
Q

SJS course - Mucous membranes:

A
  1. Lesions on mucous membranes may accompany or precede the skin rash.
  2. Mucosal surfaces may be tender and burning.
  3. Lips are often swollen, cracked, bleeding, and crusted.
69
Q

SJS - Medications (short term):

A
  1. Sulfonamide antibiotics.
  2. Aminopenicillins.
  3. Quinolones.
  4. Cephalosporins.
70
Q

SJS - Medications (long term):

A
  1. Carbamazepine.
  2. Phenobarbital.
  3. Phenytoin.
  4. Valproic acid.
  5. Piroxicam.
  6. Allopurinol.
  7. Steroids.
71
Q

EBD of SJS:

A
  1. Histopath –> Supports clinical impression.

2. Path –> Demonstrates epidermal necrosis with minimal evidence of epidermal and dermal inflammation.

72
Q

Guttate psoriasis - Textbook presentation:

A

Generally presents with small, round, and slightly oval lesions on the back and trunk.
–> Somewhat silvery, adherent scales.

73
Q

Guttate psoriasis - Description of the lesion:

A

Small 0.5-1.5cm, round and slightly oval lesions with characteristic overlying silvery scales.

74
Q

Guttate psoriasis - Character of the lesion:

A
  1. Lesions tend to occur over the UPPER TRUNK and proximal extremities.
  2. Face, ears, and scalp may also be involved.
  3. Lesions may localize to sites of minor skin trauma, such as scrapes (Koebner phenomenon).
  4. Eruption generally persists for 3-4 months and then remits spontaneously.
75
Q

Guttate psoriasis - Most commonly seen in?

A

Young adults, frequently preceded by a strep throat infection.

76
Q

Guttate psoriasis - Affected patients are at increased risk for?

A

Development of psoriasis vulgaris in the next 3-5yrs.

77
Q

EBD of psoriasis:

A
  1. Clinical diagnosis.
  2. Finding of a strep pharyngitis is supportive.
  3. Skin biopsy of an established lesion may demonstrate classic histologic findings of psoriasis vulgaris.
78
Q

Pityriasis rosea - Textbook presentation:

A

Commonly presents as a “herald patch” and then progresses to small, oval, scaly plaques over the trunk.
–> Rash is mildly pruritic.

79
Q

Pityriasis rosea - Description of the lesion:

A

Oval or round plaque with scale.

80
Q

Pityriasis rosea - Character of the lesion - Primary?

A

Primary eruption appears as a single oval or round, pink to brownish plaque with a collarette of scale around the inner margin of the lesion (the herald patch).
This herald patch most often occurs on the trunk and is often misdiagnosed as tinea corporis.

81
Q

Pityriasis rosea - Character of lesion - 1-2 weeks?

A

1-2 weeks after the appearance of the herald patch, the secondary eruption emerges as generalized smaller but similar oval scaly plaques distributed along skin tension lines in a “fir tree” pattern.

82
Q

Pityriasis rosea - Character of the lesion - Pruritus?

A

Variable degrees of pruritus.

83
Q

Pityriasis rosea - Character of the lesion - Resolution:

A

Spontaneous resolution occurs over 8-12weeks, often with subsequent post inflammatory hypopigmentation or hyperpigmentation.

84
Q

Pityriasis rosea - History?

A

A history of a mild prodrome of malaise, nausea, headache, and low-grade fever may be present.

85
Q

Is pityriasis rosea common?

A

Yes, it is a common worldwide disease without genetic or racial predilection, occurring sporadically throughout the year.

86
Q

Pityriasis rosea - Viral cause?

A

It is postulated; evidence suggests but does not confirm a role for HHV-7.

87
Q

EBD of pityriasis rosea:

A
  1. Clinical diagnosis.
  2. Skin biopsy demonstrates many non specific findings of a subacute dermatitis but can provide supportive evidence for the diagnosis.
88
Q

Tinea corporis - Textbook presentation:

A

Tinea corporis commonly presents as round, pink, plaques with small peripheral papules and a rim of scales.

89
Q

Tinea corporis - MC locations:

A

Neck and back.

90
Q

Tinea corporis - Description of the lesion:

A

Multiple lesions are possible.

91
Q

Tinea corporis - Description of the lesion - Circular lesion:

A

Sharply marginated raised border and central clearing, arising by centrifugal spread of the fungus from the initial site of infection.

92
Q

Tinea corporis - Inflammatory lesions:

A

May demonstrate pustules or vesicles, especially around the margin.

93
Q

Tinea corporis - Overlying scale?

A

Is common, typically more prominent at the border of the lesion.

94
Q

Tinea corporis - Solitary lesions:

A

May occur, or there may be multiple plaques that remain discrete or become confluent.

95
Q

Tinea corporis - Degree of associated inflammation?

A

Variable, depending on the causative species of fungus.

96
Q

Tinea corporis - Wide variation in clinical presentation:

A

Depends on:

  1. Species of fungus.
  2. Size of the inoculum.
  3. Body site infected.
  4. Immune status of the patients.
97
Q

EBD of tinea corporis:

A
  1. Identification of the fungus by microscopic examination of scales after application of 5-20% KOH.
  2. Culture of tissue material.
  3. Histopath is rarely necessary to make the diagnosis of a superficial infection –> With the use of fungal stains the cell walls may be visible in fixed sections.
98
Q

Nummular dermatitis - Textbook presentation:

A

Nummular dermatitis generally presents as an extremely pruritic rash of numerous, round, crusted lesions on patient’s legs.

99
Q

Nummular dermatitis - Description of lesions:

A

Well-demarcated coin-shaped lesions composed of minute vesicles and papules on an erythematous base.
–> Lesions have an overlying crust, frequently with a weeping exudate.

100
Q

Nummular dermatitis - Disease highlights:

A
  1. Nummular dermatitis is an acute eruption of numerous lesions predominantly on the extremities.
  2. Lesions are severely pruritic.
  3. Eruption runs a remitting and relapsing course.
  4. Patients are often atopic.
  5. 2o infection is frequently present.
101
Q

Nummular dermatitis - EBD:

A
  1. Microscopic exam of a scraping will rule out tinea.

2. Histopath can assist in the diagnosis by demonstrating the features of an acute dermatitis.

102
Q

Secondary syphilis - Textbook presentation:

A
  1. Presents as oval macules in sexually active people.
  2. Lesions are present diffusely, including on the palms and soles.
  3. A history of a transient, painless, genital ulcer in the preceding weeks can often be obtained.
103
Q

2o syphilis - Description of the lesion:

A

Papules and plaques distributed over the entire body. They are copper red to hyperpigmented in color.

104
Q

2o syphilis - Character of the lesion:

A
  1. There may be variable lesions at different stages of disease.
  2. Rashes of 2o syphilis are non pruritic.
  3. Lesions are generally symmetrically distributed.
105
Q

EBD - 2o syphilis:

A
  1. Venereal disease research lab (VDRL) and fluorescent treponemal antibody (FTA) test are 100% sensitive for 2o syphilis.
  2. FTA tests have specificities in the high 90% range.
106
Q

Urticaria - Textbook presentation:

A

Presents as an itchy rash with large or small, palpable, red areas over the entire body.
Rash is variable, with no one lesion lasting very long.
BOTH the rash and the pruritus respond to antihistamines.

107
Q

Urticaria - Description of the lesion:

A

Transient pink to red smooth flat-topped papules and plaques that may coalesce into a giant lesion.
–> Lesions often leave purple discoloration or central clearing when they fade.

108
Q

Urticaria - Characteristics of the lesions:

A
  1. Individual lesions should resolve within 24h while new lesions may continue to develop.
  2. Eruption is typically accompanied by itch, but excoriations are rare.
109
Q

Urticaria - Lasts?

A

Most is acute, lasting less than 6 weeks.

110
Q

Urticaria is a HSR to numerous insults:

A 
I-I-I-I-I
Infection
Injection
Ingestion
Inhalation
Infestation
111
Q

Chronic urticaria:

A

Can also be seen in the setting of systemic disease such as collagen vascular disease, malignancy, parasitosis, and chronic infection.

112
Q

EBD of urticaria - Morphologic DDX often includes:

A
  1. Erythema multiforme (because of the targetoid appearance of some urticaria).
  2. Insect bite reactions.
  3. Early phases of bullous pemphigoid.
113
Q

Purpura/petechiae - Textbook presentation:

A

They are seen in patients with bleeding diatheses or vascular damage.

114
Q

Petechiae are:

A

Capillary hemorrhages that present as non blanching, pinpoint, red spots over dependent body parts, most commonly the lower extremities.

115
Q

Purpura are:

A

Larger hemorrhages into the skin.

116
Q

Important point about purpura:

A

Associated with a variety of life-threatening diseases such as vasculitis and sepsis.

117
Q

Description of the lesion - Petechiae:

A

Red, blue, purple, non blanching, pinpoint spots.

118
Q

Description of the lesion - Purpura:

A

Larger (up to several cm) macules, papules, or plaques that may or may not be palpable.

119
Q

Petechiae most commonly are a sign of?

A

Thrombocytopenia.

120
Q

Purpura - The degree to which purpuric lesions are palpable is helpful diagnostically:

A
  1. Nonpalpable hemorrhage in the skin is most concerning for thrombocytopenia or abnormal platelet function.
  2. Extravasation of blood alone into deep tissue layers can produce a nodule (such as occurs with a hematoma).
  3. Edema associated with a vessel injury (such as in cases of inflammatory vasculitis) may cause a palpable lesion.
121
Q

EBD of purpura/petechiae - Evaluation of clotting:

A

Indicated to determine if purpura and petechiae are symptoms of coagulopathy OR vasculitis.

122
Q

EBD of purpura/petechiae - Why skin biopsy?

A
  1. Size + Location of affected vessels within the dermal and subcutaneous tissues.
  2. Degree + Character of associated inflammation.
  3. Type of vessel damage –> Leukocytoclastic or granulomatous.
  4. Presence + character of any occlusions within vessels (organisms, calcium, fibrin).
123
Q

Basal cell carcinoma - Textbook presentation:

A

Most commonly presents as a flesh-colored, translucent, or slightly red papule or nodule, classically displaying a rolled border.
–> MC on the head and neck of older adults.

124
Q

Basal cell carcinoma - Description of the lesion:

A

The typical lesion is a flesh-colored, translucent, or slightly red papule or nodule, classically displaying a rolled border.

  • -> Lesions are often friable, bleeding easily and developing crust. Telangiectasias on the surface can be a helpful sign.
  • -> Large tumors can be locally destructive.
125
Q

BCC - MC site:

A

Nose –> 20-30%.

126
Q

Patients have up to …% risk of developing subsequent BCCs in the 5 years after initial diagnosis.

A

45%.

127
Q

SCC - Textbook presentation:

A

MC presents as a firm but somewhat indistinct nodule.

It may evolve from actinic keratoses on the sun-exposure skin of middle-aged people.

128
Q

SCC - Description of the lesion:

A

Lesions are firm but somewhat indistinct nodules that may arise from an in situ carcinoma or in normal skin.
Tumor may become ulcerated or bleed easily and become crusted.

129
Q

SCC - Surface may be?

A
  1. Smooth.
  2. Verrucous.
  3. Papillomatous.
  4. With or without scaling.
130
Q

SCC - In situ lesions tend to be?

A

Sharply demarcated erythematous scaling plaques.

131
Q

Risk factors for SCC:

A
  1. UVB.
  2. Radiation therapy.
  3. Chronic scar formation.
  4. Chemical carcinogens - hydrocarbons.
  5. Viral exposures.
  6. Thermal exposures.
  7. Arsenic.
  8. Long-term immunosuppression (such as in renal transplant recipients).
132
Q

SCC - Metastasis:

A

Incidence varies –> 1-20% to as high as 42%.

133
Q

ORAL SCC:

A

Predominantly a disease of adult men.

–> Alcohol + tobacco.

134
Q

EBD of SCC:

A
  1. Histology is the gold standard.
  2. HIGH INDEX of suspicion is necessary –> To recognize a potential tumor when its appearance or location is unusual.
    (verrucous form of SCC may be mistaken for a wart).
135
Q

Melanoma - Textbook presentation:

A

Dark, brown macule in a middle-aged person. Lesion has pigment variation throughout and irregular borders.

136
Q

Melanoma - Description of the lesion:

A

MC type of melanoma is superficial spreading.

137
Q

Melanoma with growth?

A

Becomes GLOSSY.

138
Q

MC location of superficial spreading melanomas??

A

MALES –> Upper back.

FEMALES –> Leg.

139
Q

2nd MC type of melanoma:

A

Nodular.

140
Q

Nodular melanoma - Location:

A

Head, neck, trunk.

141
Q

Nodular melanoma - Appearance:

A

Blue-black, reddish, purplish, or even non pigmented papule or nodule.

142
Q

Acral lentiginous melanoma is seen in?

A

More pigmented races, such as Africans, Asians, and Indians.

143
Q

Acral lentiginous melanoma occurs where?

A

On the palms and soles and beneath the nail plate.

–> Diagnosis is often delayed.

144
Q

Lentigo maligna melanoma?

A

It is a rare type of melanoma found predominantly in the elderly on the sun-exposed portions of the head and neck.

145
Q

Lentigo maligna melanoma - Morphology:

A

The tumor is usually flat, with irregular borders and a diameter of several centimeters.

146
Q

Lentigo maligna melanoma - Color?

A

Varies throughout from tan to brown to black and purple and blue.

147
Q

Lifetime risk for melanoma in the USA in 1935 and in 2002?

A

1935 –> 1/1500.

2002 –> 1/68.

148
Q

Familial melanoma accounts for …-…% of cases.

A

8-12%.

149
Q

EBD of melanoma - Preferred method for obtaining tissue for diagnosis:

A

EXCISIONAL biopsy.
–> Preserves the extent of the primary tumor and all associated histologic features without disrupting the lymphatic structure.

150
Q

EBD of melanoma - Histologic diagnosis:

A

Based on a constellation of features - No single feature is diagnostic.
–> Both cytologic and architectural features are evaluated.

151
Q

Most useful way of organizing the DDX of a rash?

A

To base it on the morphology of the lesion.

Project - USMLE Step 3 (82 decks)

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