Scalp Hyperkeratosis in Children With Skin of Color: Diagnostic and Therapeutic Considerations

Scalp hyperkeratosis (scaling or flaking) is a common symptom in childhood and is typified by fine to thick hyperkeratosis of the scalp with or without underlying erythema. The causes of scalp hyperkeratosis in childhood vary based on the demographics of the population. In a population where approximately half of the pediatric patients were white, scaling of the scalp was more common in patients with seborrheic dermatitis and/or atopic dermatitis (AD) who were aged 0 to 2 years, and tinea capitis was only noted in children who were black.¹ In children with skin of color, scalp hyperkeratosis has been noted as a marker of tinea capitis, especially in patients aged 3 to 11 years,^2,3 and the level of suspicion should consistently remain high for this age group. In another study of an all-black population of schoolchildren aged 5 to 13 years (N=224), 3% demonstrated signs and symptoms of tinea capitis and 14% were found to be asymptomatic carriers.⁴ Although generally benign in nature, scalp hyperkeratosis can be associated with systemic illnesses such as juvenile dermatomyositis and Langerhans cell histiocytosis.⁵ This article addresses the diagnosis and treatment of scalp hyperkeratosis in children with skin of color, focusing on differences in exposure to contagious cases, hairstyling practices, and biological factors that may impact the disease process.

CAUSES OF SCALP HYPERKERATOSIS IN CHILDHOOD

Scalp hyperkeratosis in childhood usually is caused by common benign conditions, but some level of suspicion should be maintained for more severe etiologic conditions such as Langerhans cell histiocytosis and collagen vascular diseases (eg, juvenile dermatomyositis).⁶ Langerhans cell histiocytosis of the scalp might be obscured by background pigmentation in black children.

Scalp scaling can be a minor criterion in the diagnosis of AD. Atopic dermatitis should be suspected in Asian children with scalp scaling. Although one study in Bangladesh revealed scalp involvement in only 5.2% of pediatric patients with AD,⁷ a study in China reported an incidence rate as high as 49.7% (with a similarly high incidence of eyelid dermatitis).⁸ Children with AD also may have dry hair.⁹ Atopic dermatitis of the scalp is typified by itching, fine hyperkeratosis, and notably eczematous scalp lesions ranging from excoriated or oozing erythematous plaques to lichenification with hair miniaturization, primarily from scratch-induced breakage.¹⁰ The latter finding often is noted in black adolescent girls with long-term moderate to severe AD (personal observation).

Seborrheic dermatitis is a hypersensitivity response to yeast colonization of the scalp with Malassezia species. The infantile form is extremely common (also known as cradle cap). Characteristically, greasy yellow hyperkeratosis in fine to thick sheets is noted on the scalp in children younger than 2 years, especially infants, often with involvement of skin folds. One study noted that seborrheic dermatitis occurs in 6% of school-aged children as opposed to 19% of children younger than 2 years.¹ Severe seborrheic dermatitis in infancy may be a prelude to AD, with the incidence being 3 times higher in children with prior seborrheic dermatitis.¹¹ In teenagers, seborrheic dermatitis often accompanies acne onset in the early pubertal years.¹²

Psoriasis is an autoimmune inflammatory dermatosis that most commonly affects white children. In childhood, pityriasis amiantacea, psoriasiform scalp hyperkeratosis, is more common than in adulthood, with thick, stuck-on scales bound to the hairs. This variant is uncommon in Hispanic and Asian children and is almost never seen in black children but has been reported in cohorts of Turkish children.¹³ In a series of 85 Egyptian children with pityriasis amiantacea, diagnosis of scalp psoriasis was made in 35.3%, eczematous dermatitis in 34.2%, and tinea capitis in 12.9%.¹⁴ Consequently, a high degree of suspicion for tinea capitis should be held if pityriasis amiantacea is found in children with skin of color.^15,16

Tinea capitis is a dermatophyte infection of the scalp, hair, and surrounding skin. The presence of tinea capitis on the scalp is associated with environmental exposure to dermatophytes (eg, school, household).^4,17 The infection is largely caused by Trichophyton tonsurans in the United States, which causes a seborrheic appearance and less commonly alopecia (black dot or thinning), plaques with scale, or kerion. The presence of cervical lymph nodes and/or alopecia increases the chances of tinea being the diagnosis. Potassium hydroxide preparation and fungal culture can be performed to corroborate the diagnosis.^1-3 Other etiologies of scalp hyperkeratosis such as juvenile pityriasis rubra pilaris and lice are extremely uncommon in black children, but lice may be seen in Hispanic and Asian girls with long straight hair who attend school. Discoid lupus is more common in children with skin of color but is rare overall. When noted, accompanying mottled dyspigmentation and scarring alopecia are noted in addition to a high risk for developing systemic lupus erythematosus. Biopsy and screening for systemic lupus are necessary, as the risk for progression from discoid lupus to systemic disease is 26% over 3 years.¹⁸