The folliculitis decalvans (FD) is an orphan disease , common in consultation specialized on scalp. This disease is currently not curable, responsible for significant for patients. The pathophysiology is poorly understood, Staphylococcus aureus (SA) appears to play a role, never previously studied, and the study will attempt to clarify it.

Controversies in the literature on the pathophysiological hypotheses can be summed up as follows :

FD is it an infectious folliculitis where SA (almost always found on the lesions plays a direct role possibly aided by a lack of local immune protection , or is it a pustular inflammatory unknown cause where the SA has no direct role but is a cofactor or a simple germ superinfection.

Our study has plans to bring new evidence to help decide between these two opposite but not mutually exclusive concepts .

Inclusion Criteria:

• Adult (>18 yo)
• Alopecia
• folliculitis decalvans
• At least 6 months of evolution
• no antibiotics
• presence of pustules and crusts
• Adult (>18 yo)

Exclusion Criteria:

• immunosuppression
• pregnancy

Adult patients with Folliculitis Decalvans