Pityriasis amiantacea: a clinical and etiopathologic study of 85 patients.

Background: Studies on pityriasis amiantacea (PA) in the literature are limited and mostly retrospective. We prospectively analyzed the clinical and etiopathologic factors in a large series of PA diagnosed at our department within a defined period (2000-01).
Methods: All PA patients who attended our department were evaluated clinically and underwent bacteriologic, mycologic, and histopathologic examinations. Forty healthy control persons were similarly subjected to bacteriologic and mycologic investigations of their scalp hairs.
Results: A total of 85 PA patients were collected and studied. Pathological diagnosis of scalp psoriasis was confirmed in 35.3% of cases. Eczematous features suggesting a diagnosis of seborrheic and atopic dermatitis were detected in 34.2%. Diagnosis of tinea capitis, diagnosed by potassium hydroxide preparation, fungal culture, and periodic-acid Schiff staining, was detected in 12.9% of the PA patients. Staphylococcus isolates were detected in 96.5% of the PA patients compared with 15% in healthy persons as the control (P > 0.00001).
Conclusions: Pityriasis amiantacea represents a particular reaction pattern of the scalp to various inflammatory scalp diseases. The most frequent skin diseases associated with PA are psoriasis and seborrheic dermatitis. It is important to keep the diagnosis of tinea capitis in mind when evaluating PA patients. Staphylococci on the scalp could participate in the pathogenesis of PA.