- Define vitiligo. With what diseases is it associated?
Vitiligo is characterized by skin depigmentation of unknown etiology. It is associated with
autoimmune conditions such as pernicious anemia, hypothyroidism, Addison’s disease, and
type I diabetes. Patients often have antibodies to melanin, parietal cells, thyroid, or other
factors. - Name several conditions to think about on the Step 2 exam in patients with
pruritus.
Think of serious conditions first, such as obstructive biliary disease, uremia, and polycythemia
rubra vera (classically seen after a warm shower or bath). Pruritus also may be caused by
contact or atopic dermatitis, scabies, and lichen planus. - Define contact dermatitis. How do you recognize it? What are the classic
culprits?
Contact dermatitis is usually due to a type IV hypersensitivity reaction, although it also may
be due to an irritating or toxic substance. Look for new exposure to a classic offending
agent, such as poison ivy, nickel earrings, or deodorant. The rash is well circumscribed and
occurs only in the area of exposure. The skin is red and itchy and often has vesicles or bullae
(Fig. 6-1). Avoidance of the agent is required. Patch testing can be done, if needed, to
determine the antigen.
53 - Define atopic dermatitis. What history points to this diagnosis?
Atopic dermatitis is a chronic allergic-type condition that begins in the first year of life with red,
itchy, weeping skin on the head, upper extremities, and sometimes around the diaper area.
The clue to diagnosis is a family and/or personal history of allergies (e.g., hay fever) and
asthma. The biggest problem is scratching of affected skin, which leads to skin breaks and
possible bacterial infection. Treatment involves avoidance of drying soaps and use of
antihistamines and topical steroids. - Define seborrheic dermatitis. What part of the body does it involve? How is it
treated?
Seborrheic dermatitis causes the common conditions known as cradle cap and dandruff as
well as blepharitis (eyelid inflammation). Look for scaling skin with or without erythema
on the hairy areas of the head (scalp, eyebrows, eyelashes, mustache, beard) as well as on
the forehead, nasolabial folds, external ear canals, and postauricular creases. Treat with
dandruff shampoo (e.g., selenium or tar shampoo), topical corticosteroids, and/or
ketoconazole cream. - Name the various dermatologic fungal infections.
Known as dermatophytosis, tinea, and ringworm, fungal infections include the following:
Tinea corporis (body/trunk): look for red ring-shaped lesions with raised borders that tend
to clear centrally while they expand peripherally (Fig. 6-2).
Tinea pedis (athlete’s foot): look for macerated, scaling web spaces between the toes that
often itch and may be associated with thickened, distorted toenails (onychomycosis). Good
foot hygiene is part of treatment.
Tinea unguium (onychomycosis): thickened, distorted nails with debris under the nail
edges.
Tinea capitis (scalp): mainly affects children (highly contagious), who have scaly patches
of hair loss and may have an inflamed, boggy granuloma of the scalp (known as a kerion)
that usually resolves on its own.
Tinea cruris (jock itch): more common in obese males; usually is found in the crural folds
of the upper, inner thighs. - What organisms cause fungal infections?
Most fungal infections are due to Trichophyton species. In tinea capitis, if the hair fluoresces
under the Wood’s lamp, Microsporum species is the cause; if not, probably Trichophyton. - How are fungal infections diagnosed and treated?
Formal diagnosis of any fungal infection can be made by scraping the lesion and doing
a potassium hydroxide (KOH) preparation to visualize the fungus via a microscope or by
doing a culture. Because they are so common clinically, empiric treatment without a formal
diagnosis is common, but for the USMLE, get a formal diagnosis before treating. Oral
antifungals must be used to treat tinea capitis and onychomycosis; the others can be treated
with topical antifungals (imidazoles such as miconazole, clotrimazole, or ketoconazole) or
griseofulvin, which is better for severe or persistent infections. - True or false: Candidiasis is often a normal finding in some women and
children.
True. Oral thrush (creamy white patches on the tongue or buccal mucosa that can be
scraped off) is seen in normal children and Candida vulvovaginitis is seen in normal
women, especially during pregnancy or after taking antibiotics. However, at other time
periods and in different patients, candidal infections may be a sign of diabetes or
immunodeficiency; for example, thrush in a man should make you think about the possibility
of AIDS.