Scarring Alopecia and Lichen Planopilaris
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Direct answer
Scarring alopecia is a group of permanent hair loss disorders in which inflammation destroys hair follicles and replaces them with fibrous tissue. Primary cicatricial alopecias are classed as lymphocytic, neutrophilic or mixed, and lichen planopilaris is among the commonest lymphocytic types. Because lost follicles do not regrow, the key step is an early scalp biopsy taken from the active margin of the lesion.
What you must remember
- Permanence: once a follicle is replaced by fibrosis, hair does not regrow, so treatment aims to stop the inflammation early.
- Classification: primary cicatricial alopecias are lymphocytic, neutrophilic or mixed, and this grouping guides the choice of therapy.
- Lichen planopilaris: perifollicular scaling and erythema with burning or itching, usually affecting the vertex and crown of adults.
- Frontal fibrosing alopecia: progressive recession of the frontal hairline with loss of eyebrows, most often in postmenopausal women.
- Central centrifugal cicatricial alopecia: begins at the vertex and spreads outward, seen mainly in women of African descent, with traction from hairstyling as a risk factor.
- Pseudopelade of Brocq: patchy scarring without visible inflammation, often regarded as the end stage of several scarring disorders.
- Dermoscopy: loss of follicular openings, perifollicular scale and peripilar casts point to scarring disease, whereas the brown peripilar sign belongs to androgenetic alopecia.
- Biopsy: a 4 mm punch biopsy from the active peripheral margin shows the diagnostic inflammatory pattern, and two biopsies (vertical and horizontal sections) are ideal.
Lymphocytic, neutrophilic or mixed: a practical comparison
Scarring alopecias are sorted by the dominant inflammatory cell on biopsy, because that pattern guides treatment. Clinicians first confirm that follicles are truly destroyed, since some non-scarring disorders look similar early on.
| Group | Common examples | Clinical and histological clue |
|---|---|---|
| Lymphocytic | Lichen planopilaris, frontal fibrosing alopecia, central centrifugal cicatricial alopecia | Perifollicular erythema and scale, with a lymphocytic infiltrate around the follicle |
| Neutrophilic | Folliculitis decalvans, dissecting cellulitis of the scalp | Pustules, crusts and tufted hairs, with neutrophils in and around the follicle |
| Mixed | Acne keloidalis (folliculitis keloidalis), folliculitis necrotica, erosive pustular dermatosis of the scalp | Both lymphocytic and neutrophilic infiltrates, often in long-standing disease |
On dermoscopy, scarring alopecia shows absent follicular openings, whereas non-scarring disease keeps visible openings. In exam stems, a lymphocytic perifollicular pattern points to lichen planopilaris, while pustules with tufting point to folliculitis decalvans. Lymphocytic disease usually responds to anti-inflammatory therapy, while neutrophilic disease often needs antibiotics as well. Mixed or long-standing cases are harder to treat, because the established fibrosis cannot be reversed even when inflammation settles.
Where the exam tries to catch you
Stems on scalp hair loss usually test whether you recognise permanence and choose the correct biopsy site.
- Trap: calling every patchy scalp hair loss alopecia areata without a biopsy. Correct: loss of follicular openings on dermoscopy suggests scarring, and only histology confirms the lymphocytic or neutrophilic type.
- Trap: taking the biopsy from the centre of an old bald patch. Correct: the active peripheral margin holds the inflammatory infiltrate, while the centre often shows only fibrosis.
- Trap: relying on minoxidil alone for lichen planopilaris. Correct: minoxidil promotes growth but does not suppress the inflammation that destroys follicles, so anti-inflammatory therapy comes first.
Frequently asked questions
Which biopsy site gives the best yield in scarring alopecia?
The active peripheral margin gives the best yield in scarring alopecia, because the inflammatory infiltrate is concentrated there. A 4 mm punch biopsy is standard, ideally two, one cut vertically and one horizontally, whereas the centre of an old bald patch usually shows only fibrosis.
What distinguishes lichen planopilaris from frontal fibrosing alopecia?
Lichen planopilaris usually involves the vertex and crown, with perifollicular scale and burning or itching, while frontal fibrosing alopecia causes recession of the frontal hairline and loss of eyebrows. Both are lymphocytic scarring disorders, but frontal fibrosing alopecia is most often seen in postmenopausal women.
Why is minoxidil not the main treatment for lichen planopilaris?
Minoxidil stimulates hair growth but does not suppress the lymphocytic inflammation that destroys follicles in lichen planopilaris. Commonly used anti-inflammatory agents include potent topical or intralesional corticosteroids, hydroxychloroquine and doxycycline, which address the cause first.
Which histological feature points to scarring rather than non-scarring alopecia?
Replacement of the follicle by fibrous tissue, with loss of sebaceous glands and a reduced number of follicular units, points to scarring alopecia on histology. Non-scarring alopecia such as alopecia areata keeps an intact follicular structure and shows a peribulbar infiltrate instead.