The scalp is characterized by a high density of sweat glands and pilosebaceous units consisting of hair follicles, sebaceous glands, and arrector pili muscles. It is estimated that there are some 100,000 follicles on the scalp so this also means that there are about 100,000 sebaceous glands and associated arrector pili muscles.
Skin diseases involving the scalp can be broadly classified into inflammatory dermatoses, infections, and neoplastic (see Table 30-1). Hair on the scalp protects the skin from ultraviolet light and if absent or decreased, predisposes balding individuals to sunburns, photodamage, and photosensitivity. Likewise, the presence of hair may make cleaning the scalp surface with shampoos challenging permitting the development of scalp conditions such as dandruff and seborrheic dermatitis related to colonization of commensal Malassezia yeasts.
| Disease | Epidemiology | History | Physical Examination |
|---|---|---|---|
| Inflammatory | |||
| Allergic contact dermatitis | Common F > M Any age | Pruritic. Onset is within hours or days after contact with the allergen | Usually presents with erythema, edema, and pruritus of the forehead, eyelids, ears, and rarely the scalp |
| Atopic dermatitis | Common M ≥ F | Pruritic | Scalp involvement more commonly seen in infants |
| Cicatricial alopecias | Relatively uncommon Prevalence is reported to range from 3.2% to 7.3% of all the alopecia conditions Most common include discoid lupus erythematosus, lichen planopilaris, and central centrifugal alopecia | Hair loss may be acute or chronic and associated with itching, burning, pain, redness, and/or drainage | Visible loss of follicular ostia, evidence for scalp inflammation with erythema, scaling, pustules, and scalp bogginess (Figures 19-8, 10, 11) |
| Psoriasis | Common M > F Any age | Asymptomatic to pruritic | Red papules and plaques with silvery, thick, adherent scale can be present (Figure 9-3) |
| Seborrheic dermatitis | Common M > F Age: bimodal; peaks in infancy and adulthood | The patient typically complains of a dry, scaly, and itchy scalp | Infants usually present with “cradle cap,” pink to yellow macules and patches with white greasy scales on the scalp Commonly presents in adults with “dandruff,” white flakes with no erythema (Figure 9-7). Moderate to severe seborrheic dermatitis is characterized by erythematous plaques with white greasy scales |
| Infectious/infestations | |||
| Dissecting cellulitis | Uncommon M > F Age: 18-40 | Drainage, pruritus, and pain may all be present Considered by some to be part of the follicular triad that includes acne conglobata and hidradenitis suppurativa | Recurrent pustules, scarring alopecia, and boggy plaques with sinus tract formation are present (Figure 19-13). Staphylococcus aureus is commonly isolated |
| Folliculitis | Common M:F dependent upon etiology that may include occlusion, heat, humidity, immunosuppression, medications, disease such as diabetes, and medications | May be pruritic | Characterized by follicular 1-3 mm pustules and/or inflammatory papules |
| Head lice | Common F > M Age: 3-11, especially girls with long hair; black children are less commonly affected | Transmission is via direct contact or by fomites such as combs, brushes, hats, helmets, and headphones | The occipital scalp, posterior ears, and neck are the most commonly affected sites; pyoderma and regional lymphadenopathy may be present |
| Herpes zoster | Common F = M Primarily older individuals | Painful prodromal period | Vesicles on a red base in a dermatomal pattern |
| Tinea capitis | Most common in children 3-7 years old and relatively uncommon after puberty | May be asymptomatic or symptomatic | Characterized by adherent scale with no alopecia or with areas of alopecia that have broken hair fibers, which appear like black dots Dandruff-like adherent scale, with no alopecia Areas of alopecia may be dotted with broken hair fibers, which appear like black dots |
| Kerion | Uncommon Children are more affected than adults; animals can be the source of infection | Very tender | Characterized by inflammation and suppurative lesions on the scalp (Figure 10-3). There may be sinus formation and rarely mycetoma-like grains |
| Systemic | |||
| Dermatomyositis | Rare F > M | Intensely pruritic | Characterized by diffuse, scaly erythematous patches in the scalp with postauricular erythema |
| Bullous diseases | |||
| Pemphigus vulgaris | Uncommon M = F Onset is most common between the ages of 50 and 60 | Lesions may be painful | Flaccid blisters, crusting, erosions, and tufted hair fibers may be present |
| Pemphigus foliaceus | Uncommon M = F Onset typically after age 50-60 years, endemic to central and southwestern Brazil and Columbia | Burning sensation or pain may be present | Crusting, scale, erosions, and erythema may be present |
| Bullous pemphigoid | Uncommon M = F Onset typically after age 50 | Pruritic | Erythema, blisters |
| Neoplastic | |||
| Actinic keratosis | Common. M > F Age: >50 years. Fair skin | May be tender and persist for months to years. History of excessive sun exposure and balding. When numerous, patients may mistake these as “rash” | Skin-colored, yellow-brown, or pink gritty papules and plaques with adherent hyperkeratotic scale (Figure 17-1) |
| Cutaneous T-cell lymphoma | Uncommon M > F | May be pruritic | Eczematous or psoriasiform patches or plaques or nodules may be present |
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