Basal cell carcinoma Aziz Khan, Jonas Adalsteinsson, and Hao Feng Clinical features Basal cell carcinoma (BCC) of the skin is the most common type of skin cancer. It is most common in Caucasians and uncommon in individuals with darker skin types. When darker-skinned patients develop a BCC, it is often pigmented clinically. The major risk factor for BCC development is ultraviolet (UV) exposure in the setting…

Lichen simplex chronicus Clinical features Lichen simplex chronicus (LSC; also known as “neurodermatitis”) is a common secondary skin condition characterized by the development of thickened plaques with accentuated skin lines (i.e., lichenification). LSC is caused by chronic scratching or rubbing. Patients do not always report frequent rubbing or scratching of the affected area. Plaques are typically well demarcated but can take on irregular, ovular, or angular…

Seborrheic keratoses Layla Kazemi and Afton Chavez Clinical features Seborrheic keratoses (SKs) are common benign skin lesions found in nearly all older individuals. They typically begin to appear during the fourth decade of life and then continue to develop throughout one’s lifetime. They can develop anywhere except the palms, soles, and mucosal surfaces. They are found most often on the head and neck, extremities, and trunk,…

Acne Payal Shah and Nikita Lakdawala Clinical features Acne is most commonly located on the face, neck, back, upper chest, and upper arms where pilosebaceous units are most densely concentrated. Acne most commonly affects adolescents. Adult women have a predisposition to a jawline distribution of papules. Acne in men commonly involves the trunk. Morphology ranges from comedones (i.e., clogged open and closed pores that create whiteheads/blackheads)…

Pityriasis alba Elizabeth Dupuy and Preeti Jhorar Clinical features Pityriasis alba is a benign inflammatory skin condition that presents with poorly circumscribed hypopigmented oval or round macules, patches, or thin plaques. Pityriasis alba is generally asymptomatic; patients may seek medical attention because of the cosmetic appearance of the lesions. Occasionally, it is scaly and may cause mild pruritus. It affects children and adolescents more often than…

Melasma Casey Abrahams and Afton Chavez Clinical features Melasma is also known as “chloasma” or, colloquially, the “mask of pregnancy.” It is characterized by light to dark-brown or brown-gray patches with irregular borders that appear primarily on the face ( Fig. 7.1 ) but also on the forearms ( Fig. 7.2 ) and mid-upper chest. A centrofacial distribution on the forehead, cheeks, nose, upper lip (sparing…

Arthropod bites Campbell Stewart Clinical features Arthropods are responsible for many dermatologic complaints, including bites, stings, and infestations. They can also be vectors for numerous systemic and life-threatening diseases. The clinical manifestations of arthropod bites vary greatly depending on which arthropod is responsible. Because of the scope of this chapter and book, several arthropod reactions will not be covered, including hymenoptera (bees, wasps, hornets), centipedes, millipedes,…

Intertrigo Shivani Sinha, Gloria Lin, and Katalin Ferenczi Clinical features Intertrigo is an inflammatory condition commonly found in the intertriginous skin folds and flexures. It can be caused by multiple different conditions within the inflammatory and infectious categories. Many healthcare providers use the word “intertrigo” synonymously with candida intertrigo (CI), so for simplicity, this chapter will mainly focus on intertrigo secondary to infection. The intertriginous areas…

Hand dermatitis—with a specific focus on irritant contact dermatitis, allergic contact dermatitis, and dyshidrotic eczema Clinical features Hand dermatitis is extremely common because the hands are exposed to many environmental chemicals and irritants. The severity of hand dermatitis ranges dramatically from mild scaling in the absence of erythema to the presence of deep fissures ( Fig. 4.1 ). The vast majority (around 90%) of hand dermatitis…

Atopic dermatitis—trunk and extremities Clinical features The American Academy of Dermatology (AAD) has developed atopic dermatitis (AD) criteria that are useful in evaluating patients for AD. The three essential criteria (pruritus, typical AD pattern, and chronic/relapsing course) should be used for screening patients with possible AD. If a patient does not display all three of these features, then they are very unlikely to have AD. The…

Atopic dermatitis—face Clinical features Atopic dermatitis (AD; often referred to by patients as “eczema”) is a chronic inflammatory skin condition characterized by pruritus and pruritic, ill-defined, red, scaly papules and plaques that predominantly affect flexural surfaces (e.g., antecubital fossa, popliteal fossa). The appearance of AD lesions differs based on lesion duration. Chronic lesions are often thickened (i.e., lichenified) from chronic rubbing and excoriated from scratching; acute…