Scarring or cicatricial alopecia is a term that refers to a group of rare disorders that destroy the hair follicle and replace it with scar tissue, causing permanent hair loss. The inflammation is directed at the hair follicle, usually the upper part where the stem cells and sebaceous gland are located. Once those structures are destroyed, there is no possibility for regeneration, and permanent hair loss results.
The clinical course is very unpredictable-it can be slow and unnoticed for long periods of time or very rapid associated with severe symptoms. The skin of the scalp may show signs of inflammation (redness, scaling, pigmentation) but there is no scar. The inflammation is actually located below the skin surface. Hair loss can be associated with severe itching, tenderness, pain and burning. It is not contagious, nor hereditary and it affects men and women of all ages, but rarely affects children.
Cicatrical alopecias are classified as primary or secondary.
In primary cicatricial alopecias, the target of the destructive inflammatory process is the hair follicle. They are further classified by the type of inflammatory cells seen on scalp biopsy that could be:
- lymphocytes, as seen in:
- lichen planopilaris (LPP)
- frontal fibrosing alopecia
- central centrifugal alopecia
- pseudopelade of Brocq
- chronic cutaneous lupus erythematosus
- neutrophils, as seen in:
- folliculitis decalvans
- tufted folliculitis
- mixed (neutrophils and lymphocytes), as seen in:
- dissecting cellulitis
- folliculitis keloidalis
Meanwhile, in secondary cicatricial alopecias, the follicle is destroyed by another cause such as: severe infections, burns, trauma, radiation or tumors.