Trichoscopy of Folliculitis Decalvans: A Closer Look at "Compounding"

Compounding in Folliculitis Decalvans

Trichoscopy of the scarring alopecia folliculitis decalvans showing early (A) and late (B) stages of a phenomenon known as “compounding.”

Compounding of hairs in a patient with folliculitis decalvans. The early stage (marked “A:) shows two follicles that are about to fuse together. The follicles marked “B” have already fused. This fusing is a permanent findings.

Fusion is thought to occur from neutrophil enzymes that destroy tissue and components of the extracellular matrix and allow hairs to fuse.
Compounding occurs when adjacent follicles fuse together. A “compound” follicle has 6 or more hairs and it is not uncommon to see groupings of 10,15, 20 or more in FD.

FD is not the only condition to cause compounding but it is one of the more common. Acne keloidalis and dissecting cellulitis can also be associated with compounding of follicles.