Alopecia refers to 'hair loss' and can be classified as scarring and non-scarring forms. This article will address scarring alopecias.
Scarring alopecias are the result of permanent injury to the stem cell region of the hair follicle. Hair growth is permanently impaired. All scarring alopecias are characterized by the replacement of the hair follicle with scarring fibrous tissue. On close inspection, there is only scarred scalp without any hair follicles visible. To make the diagnosis, your dermatologist will likely take a thorough history, carefully examine your scalp, possibly perform certain blood tests and/or fungal/bacterial cultures of the area, and a take a scalp biopsy for histological examination.
Primary causes of scarring alopecias:
It is thought that genetic and environmental factors play a role in triggering these diseases that affect the hair follicle.
Lupus erythematosus (See also www.skincareguide.com/conditions/lupus.html) is a form of primary scarring alopecia. Both systemic and discoid forms may involve the scalp. Early lesions are red, scaly, irregular raised bumps (look like a plateau) and they may evolve into scars without hair. Active lesions can be aggressively treated with topical and intralesional corticosteroids.
Lichen Planopilaris (LP) is a clinical syndrome of lichen planus associated with scarring scalp alopecia. The cause of LP is unknown and it is more common in women than men. Lesions involve patchy hair loss with redness around hair follicles, follicular spines, and scarring. Lesions evolve into thin scars devoid of hair with little resemblance to the active disease. Treatment commonly involves topical, intralesional and oral corticosteroids, antimalarials and antibiotics. The average duration is 18 months with some resolving spontaneously while others may not resolve for years. If inflammation is controlled in its early stages follicular units may be preserved and subsequent hair regrowth may be possible.
Folliculitis decalvans refers to a recurrent, patchy, painful folliculitis (inflammation of the hair follicles) of the scalp causing scarring hair loss. Hair loss is thought to result from an expanding group of crusting follicular pustules leaving a centrally atrophic area devoid of hair. Frequently, tufting of hair is seen. Treatment is difficult and includes topical (i.e. fusidic acid) or long-term oral antibiotics (i.e. minocyclin or other tetracyclins).
Acne keloidalis nuchae (AKN) (Folliculitis keloidalis) refers to a chronic papular or pustular eruption localized to the occipital area and the nape of the neck resulting in keloid (scar tissue that is much larger than the original scar) formation. Although AKN is most common in young adult men with darkly pigmented skin, cases have been described in caucasians and occasionally in females. Early lesions are erythematous, firm papules, follicularly-based, found typically on the lower occiput. Close shaving of the hair is thought to cause AKN as well as rubbing by collars and picking. These aggravating factors should be avoided. Treatment depends on the severity and options include topical antiseptics or antibiotics (1% erythromycin or clindamycin), topical or intralesional corticosteroids, and surgical treatment to completely excise the affected area.
Secondary Causes of Scarring Alopecias:
Infectious agents (especially bacteria and fungi) can often cause enough follicular damage to cause scarring alopecia. (see also www.FungalGuide.ca ) A scarring alopecia is common after a cellulitis infection of the scalp. Tinea capitis is the most common fungal infection of the scalp that can cause scarring alopecia. It is caused by a dermatophyte species of fungi (fungus that is confined to the superficial layers of the skin). The goal of treatment is to eradicate the fungus to prevent the spread of infection and to prevent scarring alopecia. Tinea capitis calls for systemic antifungal therapy (i.e. terbinafine, ketoconazole).
Neoplasms can cause secondary scarring hair loss by direct destruction of hair follicles. These include basal cell carcinomas, squamous cell carcinomas, lymphomas, and metastatic tumours.
Physical agents may also cause a scarring alopecia. Scarring alopecia is common with mechanical trauma due to accidents with scalp injury. Burns may be sufficiently severe as to destroy hair follicles. Other causes of physical/chemical-induced scarring alopecia include radiotherapy and caustic chemicals (acids and alkalis).
In conclusion, scarring alopecias are caused by many conditions. It is important to recognize the hair loss early, and have it accurately diagnosed to enable prompt treatment to control the underlying cause.
Charles Lynde, MD, FRCPC is Assistant Clinical Professor, University of Toronto Canada. His special interests include paediatric dermatology, cosmetic procedures, contact dermatitis, skin cancer, psoriasis and clinical trials in acne, eczema, and psoriasis.
John Kraft, HBSc, is a fourth year medical student at the University of Toronto, with an interest in dermatology