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Lichen Planus and Lichenoid Dermatoses


Lichen Planus

  • Idiopathic disorder that can affect the skin, hair, nails, and/or mucosae (oral, vulvovaginal) and most commonly affects adults.

  • May represent a T-cell-mediated autoreactive disorder against keratinocytes whose self-antigens have been altered by trauma or infection (e.g. HCV).

  • Flat-topped (lichenoid) papules that are often polygonal in shape and purple in color may coalesce into plaques ( Fig. 9.1 ); lesions usually resolve with hyperpigmentation ( Fig. 9.2 ).

    Fig. 9.1, Lichen planus.

    Fig. 9.2, Lichen planus of the dorsal hand.

  • A characteristic finding is Wickham striae, a network of fine white lines on the surface of papules and plaques ( Fig. 9.3 ).

    Fig. 9.3, Wickham striae in lichen planus.

  • The most common cutaneous sites of involvement are the scalp, flexor wrists ( Fig. 9.4 ), forearms, genitalia, distal lower extremities, in particular the shins, and presacral areas.

    Fig. 9.4, Koebnerization of lichen planus into the site of the excision of the saphenous vein.

  • There are multiple variants of lichen planus, from exanthematous to hypertrophic ( Table 9.1 ; Figs 9.5 and 9.6 ).

    Table 9.1
    Variants of lichen planus (LP).
    AutoAb, autoantibody; BP, bullous pemphigoid; BPAG2, bullous pemphigoid antigen 2 (type XVII collagen); DIF, direct immunofluorescence; HCV, hepatitis C virus; IIF, indirect immunofluorescence; LSC, lichen simplex chronicus.
    Type Clinical aspects Comments
    Actinic LP Sun-exposed sites, especially face, neck, dorsal aspect of arms
    Red-brown annular plaques or melasma-like appearance     		Middle East
    Young adults, children
    Acute (exanthematous; eruptive) LP ( Fig. 9.5 A) Abrupt onset
    Widespread distribution     		Usually self-limited (3–9 months)
    Exclude lichenoid drug eruption, pityriasis rosea, secondary syphilis
    Annular LP ( Fig. 9.5 B) Thin raised border, with hyperpigmented or skin-colored center Favors axillae, groin/penis, extremities
    Atrophic LP ( Fig. 9.5 C) Large plaques with epidermal atrophy
    Later stage of disease     		DDx: lichen sclerosus
    Annular variant with loss of elastic fibers centrally
    Bullous LP ( Fig. 9.5 D) Bullae within pre-existing lesions Separation of epidermis from dermis with underlying lichenoid lymphocytic infiltrate
    Hypertrophic LP ( Figs 9.3 & 9.5 E) Favors shins and dorsal feet
    Thick pruritic plaques with scale
    Can develop SCC     		Average duration – 6 years
    DDx: lichen amyloidosis, LSC, rupioid psoriasis
    Inverse LP ( Fig. 9.5 F) Violaceous plaques
    Axillae > inguinal or other major body folds     		Overlap with LP pigmentosus as lesions resolve with hyperpigmentation
    LP pemphigoides Variable distribution of vesicobullae, including previously uninvolved skin Routine histopathology and DIF of bullous lesions – similar to BP; IIF: autoAb to BPAG2
    LP pigmentosus ( Fig. 9.5 G) Brown to gray-brown macules and patches in sun-exposed areas of the face and neck or intertriginous zones
    Inflammatory phase usually absent     		Skin phototypes III and IV
    Coexisting LP lesions in 20% of patients
    DDx: erythema dyschromicum perstans, resolved inverse LP
    Lichen planopilaris (see Ch. 56 ) Keratotic plugs within hair follicles with narrow surrounding red to violet-colored rim
    Hair-bearing sites, especially the scalp     		A form of scarring alopecia
    Variant – frontal fibrosing alopecia (see Ch. 56 )
    DDx for scalp: discoid LE
    Linear LP ( Fig. 9.5 H) Need to distinguish Koebner phenomenon from lesions following lines of Blaschko See Chapter 1 , Chapter 51
    DDx: lichen striatus if along lines of Blaschko
    LP/LE overlap Lesions favor acral sites
    Overlapping features     		Spectrum – from only cutaneous LE to systemic LE
    Nail LP ( Fig. 9.6 A,B); (see Ch. 58 ) Lateral thinning, longitudinal ridging, fissuring
    Dorsal pterygium     		Variant – twenty-nail dystrophy (more common in children)
    Oral LP ( Fig. 9.6 C,D) Reticular form – white lacy lines or circle with short radiating spikes (buccal mucosa)
    Erosive form ∗ – includes chronic desquamative gingivitis     		Patients can have both gingival and vulvovaginal involvement
    May be associated with HCV infection
    Ulcerative LP Plantar surface > palms
    Vulvovaginal LP (see Ch. 60 ) Inner aspects of labia minora
    Glazed erythema that easily bleeds     		DDx: lichen sclerosus

    ∗ If erosive variant plus lichenoid cutaneous lesions, DDx includes paraneoplastic pemphigus.

    Fig. 9.5, Variants of lichen planus.

    Fig. 9.6, Lichen planus of the nails and oral mucosa.

  • Histologically, a band-like infiltrate of lymphocytes is seen in the upper dermis abutting the epidermis, with apoptosis of keratinocytes (Civatte or colloid bodies) and hypergranulosis; the outline of the lower aspect of the epidermis may be sawtooth-like and melanophages are present in the upper dermis.

  • DDx: lichenoid drug eruption, lupus erythematosus, pityriasis lichenoides chronica, lichen nitidus, GVHD, and a lichenoid “id” reaction due to acute contact dermatitis to nickel (children), as well as the entities in the comments section of Table 9.1 .

  • Rx: topical or intralesional CS, topical calcineurin inhibitors, phototherapy (NB-UVB), and if severe, consider systemic therapy, e.g. oral CS, hydroxychloroquine [scalp disease], acitretin, JAK inhibitors, apremilast. Topical options for oral lichen planus are outlined in Table 59.2 .

Lichenoid Drug Eruption

  • A drug-induced eruption that has an appearance similar to lichen planus; frequently more generalized or in a photodistribution (e.g. HCTZ-induced [ Fig. 9.7 ]).

    Fig. 9.7, Lichenoid drug eruption in a photodistribution.

  • Often a latent period of months after instituting drug.

  • Lesions tend to be more eczematous, psoriasiform, or pityriasis rosea-like.

  • Most commonly incriminated drugs are angiotensin-converting enzyme (ACE) inhibitors, thiazide diuretics, antimalarials, β-blockers, TNF inhibitors, quinidine and immune checkpoint inhibitors (e.g. nivolumab).

  • Despite discontinuation of the offending drug, the eruption may be persistent, requiring treatments employed for lichen planus (e.g. topical corticosteroids).

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