Master the board step 3

Master the Boards: USMLE Step 3
This condition should be managed in a burn unit. Give oxacillin/nafcillin or
other antistaphylococcal antibiotics.
Anthrax
Bacillus anthracis is usually a cutaneous infection acquired from contact with
infected livestock. It is an occupational hazard of wool sorters. Bioterrorism
is also a potential source. A papule appears that later becomes inflamed and
develops central necrosis that is black in color; hence the name anthrax,
which is the Greek word for “coal.” Of untreated cases, 20 percent are fatal.
The diagnosis is confirmed with gram stain and culture of the lesion.
Ciprofloxacin or doxycycline is the treatment.
Malignant and Premalignant Diseases
Benign Lesions
The predominant method of distinguishing between benign and malignant
lesions is by the shape and color of the lesion. Benign lesions, such as the
junctional or intradermal nevus, have the following characteristics:
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They do not grow in size.
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They have smooth, regular borders.
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Their diameter is usually < 1 cm.
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They are homogenous in color, and the color remains constant.
Biopsy is the most accurate method of making a diagnosis. Benign lesions only
need to be removed for cosmetic purposes.
Melanoma
These malignant lesions grow in size, have irregular borders, are uneven in
shape, and have inconsistent coloring.
Biopsy diagnosis is best performed with a full thickness sample, because tumor
thickness is by far the most important prognostic factor. Treatment of melanoma
is by excision. Interferon seems to reduce the recurrence rates of melanoma.
Seborrheic Keratosis
This is a benign condition with hyperpigmented lesions occurring in the
elderly with a “stuck on” appearance. They are most common on the face,
shoulders, chest, and back.
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