Diagnosis of scalp rashes

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, February 2016.

Synonyms:

Causes of scalp rashes

Categories:

Hair and scalp disorder, Age site specific, Eczema or dermatitis, Scaly disorder, Fungal infection

Subcategories:

Pityriasis amiantacea, Seborrhoeic dermatitis of the scalp, Tinea capitis, Scalp psoriasis, Atopic dermatitis of the scalp, Discoid lupus erythematosus of the scalp, Head lice, Scalp folliculitis, Erosive pustular dermatosis, Dissecting cellulitis

ICD-10:

L21.8, B25.0, L21.0, L93.0, B85.2, L66.2

ICD-11:

EH40.00, 1G00.0, EB51.Y, 1F28.0, EC90.Y, EG30.0, EA90.50, EG30.1, EG30.Y, EA81.1, EK0Y

SNOMED CT:

395122007, 402191000, 156329007, 238608008, 402319008, 5441008, 238378003, 403497000, 81000006, 403530003, 238924007

Introduction

Patients may present with a skin problem they believe to be confined to the scalp. A full medical and focussed cutaneous history should be followed by brief examination of relevant sites.

The most common scalp symptoms are:

Itch
Soreness
Scale/flaking
Pustules/sores

Itch may be associated with the majority of skin conditions in the scalp. Soreness is less frequent.

Chronic scaly scalp disorders

Pityriasis amiantacea

Pityriasis amiantacea:

Very thick asbestos-like scale
Scale is very adherent to hair shafts
Subsequent diagnosis usually seborrhoeic dermatitis or psoriasis

Pityriasis amiantacea

Tinea capitis

Tinea capitis:

Irregular scaly plaques with moth-eaten hair loss
May have inflammatory, abscess-like kerion
Hairs are easy to extract
Positive microscopy and culture of scrapings and extracted hair
Sometimes, fluorescence on Wood light examination

Tinea capitis

Psoriasis

Scalp psoriasis:

Any age, most > 15 years
May be localised or diffuse
May be isolated to scalp or involve other body sites
Check ears, elbows, knees, nails
Circumscribed erythematous scaly plaques
Large, usually white scale
Poor response to topical therapy (various shampoos, calcipotriol, potent topical steroids)
Hair loss uncommon, but when occurs, loose hair shafts can be extracted from scaly plaques

Scalp psoriasis

Seborrhoeic dermatitis

Seborrhoeic dermatitis:

Infants or > 13 years
May be localised or diffuse
May be isolated to scalp or involve other body sites
Check ears, eyebrows, nasolabial folds
Thin salmon-pink flaky plaques, sometimes annular
Small flakes of yellow or white scale
Good, temporary, response to topical therapy (ketoconazole shampoo, mild topical steroid)
Hair loss uncommon, but when occurs, loose hair shafts can be extracted from secondarily infected, oozy plaques

Seborrhoeic dermatitis of scalp

Atopic dermatitis

Atopic dermatitis:

Any age especially children
- In infants, may overlap with seborrhoeic dermatitis
Usually diffuse and very itchy
Involves other body sites
- Scalp rash rarely prominent
- Check elbow flexures, popliteal fossae, eyelids
Ill-defined erythematous blistered or dry plaques
Lichenification
Dryness rather than loose scale
Good response to properly applied topical therapy (potent topical steroid)
Hair loss rare