Scarring alopecia, also known as cicatricial alopecia, refers to a collection of hair loss disorders that may be diagnosed in up to 3% of hair loss patients. It occurs worldwide in otherwise healthy men and women of all ages.
Each specific diagnosis within this category is fairly rare, but some examples include dissecting cellulitis, eosinophilic pustular folliculitis, follicular degeneration syndrome (previously called "hot comb" alopecia), folliculitis decalvans, lichen planopilaris, and pseudopelade of Brocq, to name a few. Scarring alopecia may also be part of a much larger condition such as chronic lupus erythematosus, where many organs of the body can be affected.
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While there are many forms of scarring alopecia, the common theme is a potentially permanent and irreversible destruction of hair follicles and their replacement with scar tissue.
Most forms of scarring alopecia first occur as small patches of hair loss that may expand with time. In some cases the hair loss is gradual, without noticeable symptoms, and may go unnoticed for a long time. In other instances, the hair loss is associated with severe itching, burning, and pain, and is rapidly progressive.
The scarring alopecia patches usually look a little different from alopecia areata in that the edges of the bald patches look more "ragged." The destruction of the hair follicle occurs below the skin surface so there may not be much to actually see on the scalp skin surface other than patchy hair loss. Affected areas may be smooth and clean, or may have redness, scaling, increased or decreased pigmentation, or may have raised blisters with fluids or pus coming from the affected area.
These visual indicators may help with diagnosis, but it is difficult to diagnose a scarring alopecia just from the pattern of the hair loss and the nature of the scalp skin. Often when scarring alopecia is suspected, one or more skin biopsies are done to confirm the diagnosis and help identify the particular form of scarring alopecia. A small biopsy of 2 to 4 mm in diameter is taken and examined under a microscope. A pathologist or dermatologist will look for destruction of the hair follicles, scar tissue deep in the skin, and the presence and location of inflammation in relation to the hair follicles.