Enfoques actuales

• Lichen planus (Greek leichen, “tree moss”;

Latin planus, “flat”) is a subacute or a chronic dermatosis that may involve skin, mucous membranes, hair follicles and nails.

• The cause of lichen planus is unknown, but several etiologies have been proposed. It is likely that both endogenous-genetic and exogenous-environmental components such as drugs or infection may interact to elicit the disease.

• The prevalence of chronic liver diseases, including primary biliary cirrhosis, alcoholic cirrhosis, hepatitis B, and especially hepatitis C, is increased.

• HLA-B8 is more common in patients with oral lichen planus as the sole manifestation,

and HLA-Bw 35 is more strongly associated with cutaneous lichen planus.

• At least two-thirds of cases occur between the ages of 30 and 60 years.

• Cutaneous eruption is characterized by small, flat topped, shiny, polygonal, violaceous papules that may coalesce into plaques (Fig. 10.13)

• The papules often show a network of white lines known as Wickham’s striae.

• Koebner phenomenon commonly seen (Fig.

10.14).

• Itching is usually pronounced.

• The four P’s – purple, polygonal, pruritic, papule- is the abbreviation used to recall the constellation of symptoms and skin findings that characterize lichen planus.

• The disease has a predilection for the flexor surfaces of the forearms (Fig. 10.15), legs (Fig. 10.16), trunk (Fig. 10.17), and the genitalia including the glans penis (Figs 10.18 to 10.20).

Fig. 10.13: Lichen planus–violaceous, flat-topped papules

Fig. 10.14: Lichen planus–wrist involved, Koebner phenomenon also seen

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• The oral lesions of lichen planus are frequently found, either as sole manifestation of the disease or associated with cutaneous involvement. Most often consist of a lacy, reticular network of coalescent papules over the buccal (Fig. 10.21) or glossal mucosa.

Besides this, it forms plaque like, atrophic, papular, erosive and bullous lesions.

• The nails are involved in about 10% of cases and show roughening, longitudinal ridging, thinning and dystrophy. Pterygium

Fig. 10.15: Lichen planus–flexor aspect of arm involved

Fig. 10.16: Lichen planus–hypertrophic violaceous papules and plaques over legs

Fig. 10.17: Lichen planus–trunk involved by typical violaceous papular lesions

Fig. 10.18: Lichen planus–an annular lesion over the glans penis

Fig. 10.19: Lichen planus–male genitalia involved by lichen planus

formation is a frequent finding (Fig. 10.22).

• Common variants of lichen planus (LP) are classified on the basis of:

A. Configuration (annular, linear, zosteriform/along Blaschko’s lines (Fig.

10.23),

B. Morphology of lesions (hypertrophic, atrophic, vesicobullous, erosive, ulcerative, follicular [planopilaris], actinic (Fig. 10.24), LP pigmentosus, perforating, guttate),

C. Site of involvement (palms and soles, mucous membranes, nails, scalp), Fig. 10.20: Lichen planus–female genitalia involved

by lichen planus

Fig. 10.21: Lichen planus–lacy white network over the buccal mucosa

Fig. 10.22: Lichen planus–pterygium unguium formation in some finger nails

Fig. 10.23: Lichen planus–transeversely aligned lichen planus along Blaschko’s lines

D. Special forms (drug induced, overlap syndrome of lichen planus/lupus erythematosus, LP pemphigoides).

Diagnosis

• The appearance of the typical papule of lichen planus is usually sufficient to make the correct diagnosis.

• Histopathology: Microscopic features, similar to the gross morphology, are diagnostic. The two major pathologic findings in lichen planus are basal epidermal keratinocyte damage and lichenoid-interface

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cytic reaction. The histologic features are summarized here:

1. Hyperkeratosis

2. Wedge shaped hypergranuloses which is responsible for the Wickham’s striae seen clinically

3. Irregular acanthosis 4. Damage to basal cell layer

5. The rete ridges are pointed at their lower end and the papillae between rete ridges are often dome shaped thus resembling the old styled bridges on rivers having tapering down pillars and domes in between. This pattern is also called as

“saw-tooth” pattern.

6. A band-like dermal lymphocytic infiltrate closely hugs the epidermis.

7. Max-Joseph spaces are seen in some cases as a sub-epidermal clear zone.

Melanin incontinence and vascular inflammatory reaction probably give purple colour to LP lesions.

Differential Diagnosis

• Classic lesions: Lichenoid drug eruption (large scaly lesions in sun-exposed areas, devoid of Wickham striae, residual pigmentation common), lichen nitidus Fig. 10.24: Lichen planus actinicus–typical hypopigmented halo around pigmented violaceous lesions over the face

(asymptomatic pinhead sized shiny papular lesions, rarely involves mucous membranes), secondary syphilis, pityriasis lichenoides et varioliformis acuta, early pityriasis rubra pilaris.

• Hyperkeratotic lesions: Lichen simplex chronicus, prurigo nodularis, lichen amylo-idosis, warts.

• Linear lesions: Lichen striatus, linear epidermal naevus, linear psoriasis.

• Annular lesions: Granuloma annulare, secondary syphilis, psoriasis

• Lichen planopilaris: For early lesions-keratosis pilaris, other follicular keratoses, Darier’s disease, early pityriasis rubra pilaris.

For advanced lesions-discoid lupus erythe-matosus, and other forms of scarring alopecia.

• Wide-spread erosive oral lesions must be differentiated from those of candidiasis (curdy white deposits which on removal leaves an erythematous base. KOH scrapping shows budding yeasts, pseudohyphae), aphthous ulcers (well circumscribed shallow ulcers with a necrotic gray centre and an erythematous halo. It usually heals in around six weeks) pemphigus (ill defined irregular buccal or palatal non healing painful erosions. Other mucosal sites may also be involved. Nikolsky’s sign positive), cicatricial pemphigoid (vesicles, persistent extensive erosions, desquamative gingivitis with eroded bleeding gums, adhesions between buccal mucosa and alveolar process and around uvula and tonsillar fossae, involvement of other mucosal sites including conjunctiva, genital mucosa, larynx and esophagus, and decreased mouth opening due to fibrosis), carcinoma (usually malignant ulcers are painless unless secondarily infected. On palpation induration of base may be present), and erythema multiforme (usually involves lips,

palate and gingival. On lips, target lesions may be identified. Vesicles, erosions and crusting are present over oral mucosa.

Associated skin lesions- target lesions may be seen over acral extensor sun-exposed areas).

Treatment

• Topical therapy: Topical glucocorticoids are typically used for mucosal and limited cutaneous disease.

• Intralesional therapy: Intralesional triam-cinolone acetonide (5 to 10 mg/mL) is effective in treating oral and cutaneous lichen planus.

• Systemic therapy:

1. Systemic glucocorticoids are often useful and effective in doses greater than 20 mg/day (e.g. 30 to 60 mg prednisolone) for 4 to 6 weeks with subsequent taper over 4 to 6 weeks.

2. PUVA photochemotherapy is usually successful in generalized cutaneous lichen planus.

3. The systemic retinoids demonstrate anti-inflammatory activity and have been used in the treatment of lichen planus.

4. Cyclosporine (500 mg) rinses in oral lichen and systemic cyclosporine in recalcitrant lichen planus has been used successfully.

5. Other agents used in lichen planus are dapsone, griseofulvin, cyclophosphamide, methotrexate, phenytoin and extracorporeal photochemotherapy.

In mucosal lichen planus, topical corticos-teroids, tetracycline, betamethasone mouth-washes 0.5 mg 3-4 times daily, topical tretinoin gel, cyclosporine mouth rinses, tacrolimus, and pimecrolimus have been used. Maintenance of good oral hygiene and replacement of amalgam or gold dental restorations with composite material is frequently of considerable benefit.

Erosive oral lichen planus may respond to oral dapsone.

Course

Lichen planus is a benign disease with spontaneous remissions and exacerbations.

Apart from hypertrophic lichen planus, most of LP lesions tend to involute after several months to a year.