Scalp Rash
Scalp Rash: Excerpt from In a Page: Signs and Symptoms
Scalp dermatitis or infection is easy to diagnose, but it can be challenging to treat. Topical therapy or topical plus systemic therapy for prolonged periods are often necessary to successfully control these disorders. Seborrheic dermatitis is a chronic condition that can be managed successfully, but is rarely “cured,” whereas tinea capitis is usually treated successfully and resolves completely. Scalp lesions due to psoriasis and discoid lupus must be treated as aspects of systemic disease.
Differential Diagnosis
- Seborrheic dermatitis (“cradle cap,” “dandruff”)
–The most common scalp condition, it occurs across all age ranges
–May be caused by Pityrosporum ovale
–An inflammatory condition that causes itching and loose, silvery-white scale on scalp, and occasionally blepharitis
–May also affect the eyebrows, nasolabial folds, external auditory canals, chin, anterior chest, upper back, and groin
–Does not cause hair loss
–The scalp is not usually erythematous, but other affected skin areas may be red, greasy, or oily
- Tinea capitis
–Most commonly caused by Trichophyton tonsurans or rarely Microsporum canis
–Presents as patches of scale and/or pruritus with broken hairs, patchy hair loss (i.e., “black dot alopecia”)
–May progress to a kerion (see below)
-
Kerion
–A boggy, tender, subcutaneous fungal
infection (dermatophyte)
–Often has associated drainage and hair loss
Scalp folliculitis
–Presents as recurrent, itchy, crusted papules
or pustules
–An overgrowth of Staphylococcus aureus
- Psoriasis
–Usually presents with plaques of thick, silvery, adherent scalp scale that overlies well-demarcated patches of erythema
–Often occurs at the ears and occipital area
–May be limited to the scalp, but often has skin disease, nail pitting, or nail dystrophy
- Dissecting cellulitis of the scalp
–Chronic, tender, boggy, often suppurative subcutaneous fluctuant masses
–Occurs in black patients
–May be associated with acne keloidalis,
which can cause a scarring hair loss at the occiput
-
Discoid lupus
–Presents initially as well-demarcated erythematous plaques of patchy, scarring scalp hair loss, then spreads centrifugally
Contact dermatitis
Workup and Diagnosis
-
History and physical examination
–If the scalp scale is diffuse, white, and nonadherent, seborrheic dermatitis is the likely diagnosis
Bacterial culture from any intact scalp pustule or suppurating area may be helpful to confirm bacterial folliculitis or dissecting cellulitis
KOH prep of scalp scale or scalp hair can be assessed under a microscope in the office to confirm the presence of endothrix (spores within the hair shaft) in the hair or branching hyphae in the scalp scale Fungal cultures can be obtained from the drainage of a kerion or from scalp scale scraped by a tongue depressor or sterile toothbrush
–Hairs from the affected area can also be sent for fungal culture to rule out tinea capitus; the hairs must be plucked so that the root of the hair is available
–Cultures may take several weeks and sensitivity varies widely based on clinician technique and lab handling
-
A punch or shave biopsy is usually unnecessary, but can aid in the diagnosis of seborrheic dermatitis
-
In cases of tinea capitis, only M. canis, which is uncommon in the U.S., fluoresces with a Wood's lamp
Treatment
-
Seborrheic dermatitis: Zinc pyrithione, ketoconazole, tar, and salicylic acid shampoos
–If monotherapy fails, the addition of a topical steroid solution or ointment (e.g., betamethasone, fluocinonide) during flareups may be useful
Tinea capitus and kerion: Systemic antifungal therapy (e.g., griseofulvin, diflucan, terbenafine, ketoconazole, itraconazole) for 4–8 weeks; steroids
-
Scalp folliculitis: Treat with 2–4 weeks of a first-generation cephalosporin or tetracycline derivative
–Topical clindamycin or erythromycin solutions may also be used
Discoid lupus and psoriasis: Intralesional steroid injection and/or systemic treatments
Dissecting cellulitis: Incision and drainage of suppurative lesions, intralesional steroids, and systemic retinoids or antibiotic therapy
Book Source Details
- Book Title: In a Page: Signs and Symptoms
- Author(s): Scott Kahan, Ellen G. Smith
- Year of Publication: 2004
- Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: In a Page: Signs and Symptoms
Authors: Scott Kahan, Ellen G. Smith
Publisher: Lippincott Williams & Wilkins
Copyright: 2004
ISBN: 1-4051-0368-X
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» Next page: RASH, LOCAL (Differential Diagnosis in Primary Care)
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