A clinical, microbiological, and histopathologic study of trichostasis spinulosa.

Trichostasis spinulosa (TSS) is a relatively common follicular disorder that can occur on the face and trunk, especially in the interscapular area. Its cause remains unclear. We examined clinically 30 patients with TSS and follicular materials extracted from each patient were examined microscopically. Bacterial culture and skin biopsy were done in 12 and 10 patients, respectively. Periodic acid Schiff (PAS) and Brown-Brenn Gram stain were used for detection of pityrosporum (malassezia) and bacteria. The interscapular area (14/30), nose (8/30), and cheek (4/30) were common sites of TSS. Pityrosporum and bacteria in the extracted follicular material were found at the rates of 82.6% and 73.3%, respectively. In histologic examination, follicular hyperkeratosis and numerous vellus hairs enveloped within keratotic sheath were common features. Pityrosporum and bacteria were found at the rate of 70% in biopsied specimens on PAS and Brown-Brenn Gram stain. In bacterial culture, Propionibacterium acne was most commonly identified in 75% (9 out of 12 patients). Pityrosporum and bacteria, especially Propionibacterium acne, were commonly found in the extracted follicular material and biopsied specimens. Thus, they may be related to the induction of follicular hyperkeratosis with retention of vellus hairs, and we suggest that these microorganisms may be one of the possible etiologic factors of TSS.