Dermatology

Missed Concepts

• Lichen Planus diagnosis is clinical, but a punch biopsy of prominent lesion can be sent to confirm, presents with purple, polygonal, pruritic, papules and plaques, sometimes with Wickham striae.
• Pityriasis rosea has the classic herald patch and Christmas tree pattern, ddx includes secondary syphilis (involves palms and soles), tinea corporis, nummular eczema, psoriasis
• Hair loss: ddx male pattern baldness, tinea capitis (scaling and inflammation), alopecia areata (well demarcated, smooth, circular)
• Ichthyosis vulgaris is a familial dry fish-like scaly rash, worse in winter and fall, predominantly on the extensor surfaces of the legs. Treat with long baths to remove scales and urea-containing lotions
• Keloids are treated with intralesional glucocorticoids
• Seborrheic dermatitis, presenting as erythematous, pruritic plaques with greasy scale on the scalp, central face, and ears is associated with Parkinson disease and HIV and is treated with selenium sulfide or ketoconazole shampoos.
• Axillary skin tags are associated with obesity, diabetes, insulin resistance, and metabolic syndrome.
• Desmoid tumors are slowly growing and locally recurring benign tumors.
• Cherry angiomas are benign and don't require further workup.

Derm Terms

• Macule/Patch, Papule/Plaque, Nodule/Tumor (2 cm cutoff), Vesicle/Bullae/Pustule

Atopic Dermatitis

• H&P: Eczema in infants is more common on extensor surfaces, in children/adults it is predominantly on flexor surfaces. Atopic triad. Frequent skin infections. Pruritis leading to lichenification. Can be triggered by allergens (contact dermatitis)
• Dx: Clinical. Associated with increased serum IgE. Ddx includes impetigo, seborrheic dermatitis, contact dermatitis
• Tx: Emollients. Topical steroids for flares. Prognosis for childhood eczema is good, with most patients having complete resolution by adulthood.

Contact Dermatitis

• H&P: Can have a clear border (allergic, type IV hypersensitivity, e.g nickel, poison ivy) or not (irritant, e.g. nickel, makeup, detergents).
• Dx: Erythematous, pruritic, papules and vesicles, sometimes with erosions, crusting, excoriations, and lichenification. Patch testing.
• Tx: Avoid causative agents, cold compresses and oatmeal baths ± short course of topical steroids. For severe and widespread cases short course of oral steroids.

Psoriasis

• H&P: Immune mediated, probably genetic. Associated with arthritis of the DIP joints.
• Dx: Well demarcated pink plaques with silvery scale on extensor surfaces, scalp, and gluteal cleft. Nails can have pitting and onycholysis (separation from nail bed).
• Tx: Topical steroids (low potency for face/intertriginous areas, high potency for extensor surfaces), vitamin D analogs, retinoids; For generalized (>30% of the body), use UVB or PUVA; severe cases (e.g. psoriatic arthritis) warrant methotrexate, anti-TNF agents.

Erythema Nodosum

• H&P: F>M. Causes remembered with mnemonic NoDOSUM—None, Drugs, OCPs, Sarcoidosis, Ulcerative colitis, Micro (strep, cocci, TB). Most frequently presents on the shins as tender red/violet poorly demarcated nodules without ulceration. May have preceding fever, malaise, myalgias
• Dx: Clinical. Ddx includes cellulitis, trauma, thrombophlebitis
• Tx: NSAIDs; potassium iodide or systemic corticosteroids for severe cases

Rosacea

• H&P: Fair skin, light-eyed people, with history of flushing. Erythema and inflamed papules on face, nose, forehead, chin without comedones, rhinophyma (enlarged irregularly textured nose) appears late. Conjunctival injection, eyelid telangiectasias, and dry eyes are also common.
• Dx: Clinical. Ddx includes acne.
• Tx: Topical metronidazole; oral doxycycline or minocycline; clonidine for flushing.

Erythema Multiforme

• H&P: Inflammatory type IV hypersensitivity reaction. Etiologies include HSV, M. pneumonia, and sulfa drugs, preceded by malaise, fever, burning. Sudden onset, rapidly progressive lesions. Crops of targetoid pruritic papules mostly on the hands, soles, and limbs. - Nikolsky. EM, SJS, and TEN lie on a spectrum with TEN being the worst (involving >30% BSA, high mortality).
• Dx: Clinical. Differential includes SJS and TEN, both of which have + Nikolsky and spread from the face and trunk outwards.
• Tx: H2 blockers for pruritus; prednisone for 1-3 weeks; azathioprine in refractory cases

Pemphigus Vulgaris

• H&P: Autoimmune disease targeting desmoglein. Flaccid bullae and erosions, oral lesions precede skin lesions. + Nikolsky sign.
• Dx: Skin biopsy. "Tombstoning" on immunofluorescence. Differential includes EM, SJS, TEN
• Tx: Corticosteroids and immunosuppressives. Can affect the esophagus.

Bullous Pemphigoid

• H&P: Autoimmune disease against skin basement membrane. More common than pemphigus vulgaris. Age > 60 (median 80). Large, tense, bullae and erythematous patches. - Nikolsky sign.
• Dx: Skin biopsy. Differential includes pemphigus, dermatitis herpetiformis, porphyria cutanea tarda
• Tx: Topical steroids

Acne Vulgaris

Treatment of Acne Subtypes

Acne Type	Treatment
Comedonal	Topical retinoids
Inflammatory	Topical retinoids + Benzoyl peroxide > Topical antibiotics > Oral antibiotics
Nodulocystic	Topical retinoids + Benzoyl peroxide + Topical antibiotics > add Oral antibiotics > Oral isotretinoin

• Doxycycline can cause photosensitivity
• Dx: Clinical. Differential includes rosacea (no comedones) and folliculitis (different distribution)

Herpes Zoster

• H&P: Reactivation of VZV that was dormant in DRG. Risk factors are age and immunosuppression. Painful vesicles in a dermatomal distribution.
• Dx: Clinical. Differential includes contact dermatitis.
• Tx: Herpes zoster is non-infectious when all the vesicles have crusted over. Patients should cover the lesions when in public to avoid spreading. Treatment of shingles is with NSAIDs, topical capsaicin, seven days of oral valacyclovir initiated within 72 hrs. Vaccinate people over age 60.

Dermatophytes

• H&P: Pruritic, well demarcated, central clearing.
• Dx: Clinical, or with KOH prep. Tinea capitis is erythematous, scaly, pruritic, and associated with hair loss
• Tx: Oral meds for onychomycosis (terbinafine) and tinea capitis (griseofulvin, itraconazole). Topical azaleas, terbinafine, or griseofulvin for others. Selenium sulfide for tinea versicolor.

Basal Cell Carcinoma

• H&P: Most common skin cancer. Related to sun exposure. Slow growing. Rare metastasis. Pearly papules with central depression/ulceration, sometimes with a rolled border.
• Dx: Skin biopsy shows "palisading cells with retraction".
• Tx: Curettage, cryosurgery, radiation, or excision. Mohs for the face.

Squamous Cell Carcinoma

• H&P: Second most common skin cancer. Pink plaques with scale and erosions. Most SCC develops from actinic keratosis, but other risk factors include smoking, immunosuppression, occupational exposures, and arsenic. Actinic keratosis presents as chronic, erythematous, scaly/gritty, discolored papules and rough plaques on sun-exposed areas of skin.
• Dx: Skin biopsy
• Tx: Surgical excision. Actinic keratosis can be treated with topical chemo or liquid nitrogen. Mohs for the face, ears, or areas of tight skin and cosmetic importance.

Melanoma

• H&P: Most deadly skin cancer by far. Risk factors are sun exposure, fair skin, large number of nevi, family history.
• Dx: ABCDEs for moles. Skin biopsy shows melanocytes with cellular atypia.
• Tx: Surgical excision.