What Are These Thick Clumps of Scalp Scales Binding a Boy’s Hair?
A 3-year-old boy developed thick scales that were binding tufts of hair on his scalp. The scales had appeared 1 year ago. During infancy, he had seborrheic dermatitis that presented with diffuse scaling and crusting of the scalp and erythematous, sharply demarcated patches with yellow-white scales in the postauricular areas.
The child was otherwise healthy. There was no personal or family history of atopic dermatitis or psoriasis.
Physical examination revealed thick, asbestos-like, silvery scales, adherent to clumped hair shafts at their base, covering the vertex of the scalp. Patchy alopecia was present in the affected area. Erythematous patches with yellow-white, greasy scales were observed in the postauricular area, as well. The rest of the physical examination findings were normal.
What’s your diagnosis?
(Answer and discussion on next page)
Answer: Pityriasis amiantacea
Results of a potassium hydroxide preparation wet-mount examination of the scale and hair and a bacterial culture of the scale were negative for microbial infection. Wood lamp examination of the scalp was also negative.
A diagnosis of pityriasis amiantacea secondary to seborrheic dermatitis was made.
Daily shampooing was encouraged, and the parents were encouraged to remove the debris with a wet washcloth once the hair has been moistened for 5 to 10 minutes in the bath. After the bath, betamethasone–salicylic acid lotion was to be applied nightly until the debris was gone, followed by betamethasone valerate lotion, 0.1%, twice per week preventively for 2 weeks, then once per week for the next 3 months or longer. After 5 months of treatment, the patient showed dramatic improvement, with resolution of all the adherent scales.
Pityriasis amiantacea is a clinical syndrome that affects the scalp and is characterized by thick, silvery to waxy, adherent scales that tenaciously bind down tufts of hair.1 The word amiantacea is derived from the French word for asbestos, amiante. The condition was first described by Baron Jean-Louis Alibert in 1832 under the title La Porrigine Amiantacée.2 His description was as follows: “The characteristic shiny silvery mica-like scales which adhere to each other and surrounding hair shafts like wax surrounding the wick of a candle. They resemble the fine scales surrounding the small feathers of young birds, known to naturalists as ‘asbestos’ or ‘asbestos-like’ scales.”2 The term pityriasis amiantacea is preferred to tinea amiantacea, since the disorder usually is not a result of fungal infection.
The prevalence of pityriasis amiantacea is not known, but it is an uncommon condition. In one study, 46 cases of pityriasis amiantacea were seen during a 4-year period at the Department of Dermatology at Sahlgren’s and Lundby Hospitals in Göteborg, Sweden.3 In another study, 71 cases of pityriasis amiantacea were seen during a 5-year period at the St. John’s Hospital for Diseases of the Skin in London, England.4 The condition occurs at all ages although much more frequently in infants, children, and young adults.5,6 There is a slight female predilection.2,6,7
Etiology and Pathogenesis
The exact etiology of the condition is not known. Presumably, pityriasis amiantacea represents a particular reaction pattern to various inflammatory diseases on the scalp, such as seborrheic dermatitis, tinea capitis, bacterial infection, psoriasis, atopic dermatitis, lichen planus, lichen simplex chronicus, and pityriasis rubra pilaris.1,7,8 Occasionally, it may be a manifestation of Darier disease.7,9
Histologic features of the affected scalp are diffuse hyperkeratosis and parakeratosis with follicular keratosis in the stratum corneum, which surround each bound-down hair shaft with a sheath of horn resembling asbestos.1,8 Disease associations add other diagnostic features of the underlying disease.1
Clinically, pityriasis amiantacea presents with heavy and thick, silvery to waxy, adherent scales that tenaciously surround and bind down tufts of hair.1 Scales are arranged in an overlapping manner like flakes of asbestos, hence its name amiantacea. Most commonly, it is a localized condition, but it also may be widespread, affecting the entire scalp. On removal of the scales, the entire stratum corneum and hairs in the affected area are usually pulled off as a unit.5 The underlying scalp may show inflammation of variable severity.
The diagnosis is mainly clinical, aided by dermoscopy. Typically, dermoscopy shows scale crusts attached to hair shafts, encasing them like a sheath resembling amianth or asbestos. Wood lamp examination, potassium hydroxide wet-mount examination of scalp scrapings of the active border of the lesion, bacterial culture, and, if necessary, a biopsy of the affected scalp can be helpful for diagnosing an underlying cause. Referral to a dermatologist should be considered, as well.
Differential diagnosis includes seborrheic dermatitis, atopic dermatitis, and psoriasis. In these conditions, the flaky scales usually only are adherent to the scalp but not as concentric bundles of matted scales that tenaciously surround and bind down tufts of hair.
Temporary alopecia is a common complication of pityriasis amiantacea.6 Rarely, permanent scarring alopecia with permanent disfigurement may result if the condition is not treated.6 The latter may have a significant negative impact on the quality of life.
The underlying cause of pityriasis amiantacea should be treated if possible. Timely and effective treatment and consideration of referral to a dermatologist are essential to prevent scarring alopecia. More frequent shampooing and physical debridement also are helpful. The condition often responds to empiric treatment with topical corticosteroid lotions or shampoos, topical antifungal lotions or shampoos, and/or keratolytic agents such as salicylic acid.2 n
Alexander K. C. Leung, MD, is a clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary.
Benjamin Barankin, MD, is medical director and founder of the Toronto Dermatology Centre.
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2. Alibert JL. La porrigine amiantacée. Monographie des Dermatoses. Vol 1. Paris, France: Germer Baillière; 1832:293-295.
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8. Verardino GC, Azulay-Abulafia L, de Macedo PM, Jeunon T. Pityriasis amiantacea: clinical-dermatoscopic features and microscopy of hair tufts. An Bras Dermatol. 2012;87(1):142-145.
9. Hussain W, Coulson IH, Salman WD. Pityriasis amiantacea as the sole manifestation of Darier’s disease. Clin Exp Dermatol. 2009;34(4):554-556.