From keratinocytes located in the epidermis, just above the basal layer.
In a myriad of morphologic variants, although typicallymas a scaly, erythematous, and hyperkeratotic plaque,
often with superficial ulceration and no defined translucent border.
Actinic (or solar) keratosis (literally “sun-induced”; aktis, ray in Greek) is the most common premalignant
lesion in humans. It is a sun-related growth that affects an estimated 60% of individuals older than 40,
typically the fair-skinned and blue-eyed easy burners, who tan poorly and have occupations/hobbies that
expose them to lots of sun. Most have at least one actinic keratosis per year. Many have several.
Histologically, AK represents a partial-thickness atypia of the epidermis and, if left untreated, may degenerate into squamous cell carcinoma (SCC). Lesions usually develop as a single, small erythematous plaque, 3–10 mm in diameter, typically located over exposed surfaces, such as nose, forehead, temples, cheeks, ears, bald scalp, forearms, and dorsum of the hands (but also the back, chest, and legs). The lesions have an erythematous base that is usually covered by a scale (hyperkeratosis), often on a background of solar damaged skin, with telangiectasias, elastosis, pigmented lentigines, and multiple erythematous
keratoses. They flare and become more visible during time of immune suppression, acute sun exposure, or
One in 20 eventually breaks through into the dermis, becoming invasive and possibly
metastatic. These are typically the most elevated, erythematous, and indurated. Although more common
in older individuals, AK may also affect people in their 20s and 30s, especially fair-skinned redheads and
blonds who do not use sunscreen and live in the “sun belt” (Australia is the nation with the highest AK
Common wart: Often referred to as verruca vulgaris, it presents as a rough-surfaced, scaly, and
circumscribed papule, <1 mm to >0.5 cm in size. Most commonly located on hands and knees,
although it can occur anywhere. Often accompanied by “black seeds” (i.e., thrombosed capillaries).
Usually asymptomatic, warts may cause cosmetic disfigurement or tenderness.
Filiform wart: Long and slender growth, usually around lips, eyelids, or nares
Condyloma: A genital wart, mostly of the anus, vulva, or glans. Presents as a flat-topped papule with
an irregular surface. Condylomata may be pink at first, but turn tan or brown with time.
(Palmo)plantar wart: Involving the soles or dorsi of feet, but also toes. Often callused, it presents as a
white, irregularly surfaced area—with or without black dots. Plantar warts are usually painful, and
when extensively involving the soles, they may impair ambulation. Deep palmoplantar warts are also
termed myrmecia (from the Greek murmekos, ants). They begin as small shiny papules that progress into
deep and sharply defined rounded lesions, with a rough keratotic surface and a smooth collar of thickened horn. Since they grow deep, they are more painful than common warts.
Flat wart: Also called “plane warts” (or verruca plana). Flat and flesh-colored papules, >1–5 mm in
size. Smooth or slightly hyperkeratotic, they may number just a few or in the hundreds, at times
becoming grouped or confluent, and often acquiring linear distribution after scratching or trauma
(Koebner’s phenomenon). Although possible anywhere, they typically involve the face,shins, and dorsum of hands. May regress spontaneously, often after an inflammatory flare.
By direct or indirect contact, especially when the normal epithelial barrier has been disrupted.
Benign, keratotic (rough-surfaced), mucocutaneous proliferations due to human papilloma viruses (HPV).
There are more than 150 known types of HPV, whose manifestations include common warts, genital warts,
deep palmoplantar warts, and flat warts. Ubiquitous, they affect 7–12% of the general population, 10–20%
of school-aged children, and an even greater percentage of immunosuppressed patients and meat handlers
(“butcher warts”). They are difficult to treat and may resolve spontaneously.
Impetigo, insect bites, contact dermatitis, porphyria cutanea tarda, and lupus erythematosus.
By its classic and fleeting lesions. Always inquire about association with medicine intake, food exposure,
recent illness, and physical stimuli, but delay work-up for underlying causes until the problem becomes
chronic. Then, do a thorough physical exam, a complete blood count and differential, biochemistry
screening, urinalysis, hepatitis B surface antigen, sinus films, oral examination, stool specimens for ova and
parasites, and an elimination diet.
1. Hereditary angioedema: Autosomal dominant, it presents in the second to fourth decade of life with
sudden attacks of angioedema that often last for days and can be life threatening. Due to low or nonfunctional C1 inhibitor, with diagnosis being suggested by a low C4 level.
2. Physical urticarias: appear in response to a stimulus, such as cold, sunlight, trauma, water:
Dermatographism (wheals at site of skinstroking)
Pressure urticaria (severe swelling with deep pain several hours after localized pressure is applied, most commonly on feet and buttocks)
Aquagenic urticaria (elicited by water, as in a cold or hot shower)
Cold urticaria (from rewarming of skin exposed to cold; most common on hands and feet)
Solar urticaria (urticaria on unshielded skin after exposure to sunlight)
Cholinergic urticaria (on face and trunk, pruritusi nduced by exercise and emotional stress)
Acute urticaria resolves in 4–6 weeks. It is usually associated with drugs (penicillin, sulfonamides,
aspirin); food allergens (e.g., chocolate, shellfish, eggs, cheese, nuts, peanut butter, berries, tomatoes,
strawberries); new pets; or infections (upper respiratory infection, especially streptococcal in
children). Pregnancy may aggravate it into pruritic and urticarial papules and plaques of pregnancy
Chronic urticaria is instead longer than 6 weeks and may last for years. One half of patients are free of
symptoms at 12 months, but 20% have lesions that persist for decades. In 80% of cases, the etiology
remains unknown, with possibilities including the same causes of acute urticaria, as well as cryoglobulins, autoimmune diseases, food additives, inhalants, viruses (hepatitis B), parasites, arthropods (scabies and fleas), neoplasms, and even stress (often responding to hypnosis). Still, physical factors are the
most commonly identifiable etiologies of chronic urticaria, being responsible for one out of five cases.Among them are cold, water, sun, pressure, vibration,and even stroking (demographism), often coexistingin the individual patient. Physical urticarias are easily recognized by challenged test.