|Classification and external resources|
|ICD-10||L44.8 (ILDS L44.870)|
Pityriasis amiantacea (also known as "Tinea amiantacea") is an eczematous condition of the scalp in which thick tenaciously adherent scale infiltrates and surrounds the base of a group of scalp hairs. It does not result in scarring or alopecia. :647
Pityriasis amiantacea was first described by Alibert in 1832. Pityriasis amiantacea affects the scalp as shiny asbestos-like (amiantaceus) thick scales attached in layers to the hair shaft. The scales surround and bind down tufts of hair. The condition can be localised or covering over the entire scalp. Temporary alopecia and scarring alopecia may occur due to repeated removal of hairs attached to the scale. It is a rare disease with a female predilection.
Pityriasis amiantacea can easily be misdiagnosed due its close resemblance to other scalp diseases such as psoriasis, seborrhoeic dermatitis or lichen planus. However in pityriasis amiantacea the scales are attached to both the hair shaft and the scalp. Pityriasis amiantacea may be present with other inflammatory conditions such as atopic dermatitis or seborrhoeic dermatitis and sebaceous scales and alopecia can occur. According to the dermatology text Bolognia  this condition is most often seen in psoriasis, but may also be seen in secondarily infected atopic dermatitis, seborrheic dermatitis, and tinea capitis.
The bacteria staphylococci are present in the majority of cases. Treatment with systemic antibiotics and coal tar shampoo can completely clear the condition when Staphylococcus aureus bacteria are found. Fungal infections such as tinea capitis are known to mimic the symptoms of the condition  and can be cleared with antifungal treatment.
- Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.
- Alibert JL. La porrigine amiantacea. Monographie des Dermatoses. Paris, France, 1832: 293-5.
- Abdel-Hamid IA, Salah AA, Moustafa YM, El-Labban AM. Pityriasis amiantacea: a clinical and etiopathologic study of 85 patients. Int J Dermatol 2003; 42: 260-4.
- Raquel M. Shalev, Arnon D. Cohen, Evgeny Medvedovsky, Stella Sashavinsky, Theodore Tchetov and Daniel A. Vardy. Pityriasis Amiantacea Associated with Staphylococcus aureus Super-infection in Bedouin Patients. Microbial Ecology in Health and Disease 2004; 16: 218-221
- Bolognia et al. Dermatology, Second Edition, pg 122
- M. Ginarte, M. Pereiro Jr, Virginia Ferna´ndez-Redondo and Jaime Toribio Case Reports. Pityriasis amiantacea as manifestation of tinea capitis due to Microsporum canis. mycoses 2000, 43, 93–96