Parapsoriasis

Lichen Planus The typical early lesion is a polygonal, flat-topped, shiny papule. In the later stages, fine scales may appear on the surfaces of the lesions. Histopathologic examination may aid in differential diagnosis. Topical corticosteroid therapy is beneficial in symptomatic patients. Lichen planus is a papulosquamous skin disease that affects both men and women. The exact incidence is unknown. Some authors have suggested a seasonal variation, with the peak incidence occurring in the spring and the summer.(1) An increased frequency of tissue antigens HLA-B7, HLA-A3,(2) HLA-5 and HLA-28(3,4) has been found among patients with lichen planus. In addition, 1.5 percent of patients have a family history of the disease.(5-8) Compared with nonfamilial cases, familial cases occur earlier in life, have a more generalized distribution and are characterized by a more acute course.

Clinical Features

The primary lesion is a polygonal, flattopped, shiny papule with retained skin lines. The papules are often violaceous and tend to cluster in serpiginous or linear streaks. Fine adherent scales may appear on the surface of the lesion in the later stages.

In many cases, the lesions are relatively localized and favor the flexor surfaces of the wrists and forearms and the extensor surfaces of the lower extremities. Occasionally, the lesions are generalized on the trunk and extremities. Disseminated lichen planus usually has an acute onset and produces intense pruritus.

A so-called isomorphic reaction, consisting of the development of new lesions in sites of trauma, is a characteristic of lichen planus. Papules may become tan to brown in people with increased pigmentation, and residual postinflammatory hyperpigmentation may sometimes remain after the resolution of lesions. Hypopigmented postinflammatory macules may also occur but are not common.

When the plaques are predominantly annular, they may be confused with another common dermatosis, granuloma annulare. Lichen planopilaris and Graham Little syndrome are terms used to describe a variant characterized by perifollicular papules, particularly in hair-bearing areas such as the scalp.(9) Wickham's striae (lacy, whitish streaks across the papules) are an additional feature of diagnostic importance.

MUCOUS MEMBRANE INVOLVEMENT

Oral lesions are present in many patients with lichen planus and, because of their characteristic apperance, they are considered an important clue to the clinical diagnosis.(10-12) Appearing as white, lacy or reticulated streaks, oral lesions are most commonly located on the buccal mucosa, followed by the lips, gums and tongue.(13) Involvement is usually bilateral. Most oral lesions are asymptomatic, but those that ulcerate usually produce pain and discomfort. Some oral lesions, particularly those on the tongue, may cause an intense burning sensation. The vagina, penis, conjunctiva and larynx are only rarely involved.

NAIL INVOLVEMENT

Nail involvement is a characteristic feature of lichen planus and occurs in up to 10 percent of patients.(14) Diffuse thinning, longitudinal grooving and distal splitting are the most typical degenerative changes in the nail plate. Other abnormalities, such as koilonychia, longitudinal streaking and diffuse subungual hyperpigmentation, are found only in the most severe cases. Only one nail, several nails or all nails may be involved. "Twenty nail" dystrophy is a disorder characterized by extensive lichenoid-like involvement of all nails in the absence of cutaneous manifestations.(15) It runs a protracted but usually self-limited course and is considered by many to be a variant of lichen planus.

CLINICAL VARIANTS

Although most of the descriptive names are self-explanatory, at least three of them deserve discussion. Lichen planus follicularis, also known as lichen planopilaris, may involve the scalp, but the glabrous skin may be spared. While scalp lesions are usually distinctive, skin biopsy may be necessary for diagnosis. Advanced lichen planopilaris destroys the hair follicles and is one of the best understood causes of scarring alopecia.

Lichen planus tropicum, which is particularly common in the Middle East, appears to be an asymptomatic photosensitivity reaction. The eruption occurs in spring and summer months and consists of annular papules.

Lichen planus pemphigoides exhibits the clinical and immunologic features of lichen planus and bullous pemphigoid. With this disease, blisters form in areas that may or may not be affected with lichen planus. Direct immunofluorescence of the lesions reveals deposits of IgG and C3 at the basement membrane zone.(16,17)

Histopathology and Immunopathology

Histologic examination of a lesional skin biopsy reveals hyperkeratosis, hypergranulosis and acanthosis of the epidermis, with a characteristic saw-toothed appearance of the lower epidermal outline. The dermoepidermal junction is characterized by foci of hydropic degeneration and by an intense band-like infiltrate composed of lymphocytes and melanophages.(18)

Direct immunofluorescence studies of lesional biopsies reveal subepidermal colloid bodies that stain positive for IgM, IgA and, less frequently, IgG and C3. A band-like deposit of fibrin is often seen about the dermoepidermal junction.(19,20)

Differential Diagnosis

Other papulosquamous skin eruptions, such as guttate parapsoriasis, lichen nitidus and secondary syphilis, may mimic lichen planus. Dermal granulomas, such as granuloma annulare and sarcoidosis, often appear as deep-seated papules arranged in rings. Epidermal changes, however, are not present in granuloma annulare and sarcoidosis. In doubtful cases, diagnosis rests on histologic examination.

Course and Prognosis

Lichen planus usually develops insidiously, with slow progression to multiple areas. With therapy, complete clearing occurs within nine months in 50 percent of patients and within 18 months in 85 percent of patients.(21,22)

Patients with an acute onset of multiple generalized lesions may be more symptomatic than patients with a gradual onset of disease, but the lesions tend to clear sooner than those that develop insidiously. Certain clinical variants of lichen planus, such as hypertrophic lesions of the oral mucosa and follicular lesions, are known to be chronic in nature.

Controversy exists over the possible premalignant potential of oral lichen planus.(23-25) The development of squamous cell carcinoma has been demonstrated in long-standing lesions of oral lichen planus, particularly in the atrophic variant.(26,27) Critics, however, point out that biopsy documentation of the initial diagnosis of lichen planus has been insufficient in some studies. Without biopsy, the oral plaques of lichen planus may be difficult to distinguish from leukoplakia, a disorder with an established premalignant potential. In addition, carcinogenic risk factors, such as tobacco use, probably play a role in some patients.

Drug-Induced Lichenoid Eruptions

An eruption clinically indistinguishable from lichen planus may develop from contact with derivatives of p-phenylenediamine (PPDA), which is found in color-film developing agents, or as a side effect of systemic therapy with a number of medications.(28-30) Certain histologic features, such as parakeratosis, a deep perivascular inflammatory component and an admixture of eosinophils and plasma cells, may be helpful in distinguishing drug-induced lichenoid eruptions from classic idiopathic lichen planus.

Treatment

Potent topical corticosteroids are often required to control chronic plaques of lichen planus. Corticosteroid therapy is most effectively administered by means of corticosteroid-saturated tape, in an overnight occlusive dressing or as an intralesional injection. Judiciously used systemic corticosteroids are helpful in patients with generalized lichen planus, particularly those with acute-onset disease. The distinct benefits of systemic corticosteroids are clearly offset by numerous side effects, precluding the use of systemic corticosteroids in chronic cases.

Oral griseofulvin (Fulvicin, Grifulvin V, Grisactin) has produced sustained remission of cutaneous lichen planus in several clinical trials,(31,32) although the treatment results in patients with oral lichen planus have been disappointing.(33) Elimination of the offending medication leads to resolution of drug-induced lesions. Oral photochemotherapy may be beneficial in some cases of generalized lichen planus.

Reticular lesions of oral lichen planus may initially respond to topical retinoic acid, only to relapse on withdrawal of treatment.(34,35) Studies of systemic isotretinoin (Accutane) for the treatment of oral and cutaneous lichen planus have yielded both encouraging(36-38) and disappointing results.(39) A synthetic aromatic retinoid, etretinate (Tegison), appears to be beneficial in cutaneous and, especially, oral variants of lichen planus.(40,41)

Final Comment

The universal occurrence of lichen planus makes it imperative for a physician of any specialty to be able to identify this disorder. The chronic clinical course may be a source of frustration from the therapeutic standpoint. Recent advances in cellular and molecular biology, such as gene cloning techniques, may prove helpful in elucidating the cause of the disease.

PHOTO : Typical primary lesions of the lichen planus, presenting as polygonal, shiny papules with

PHOTO : violaceous bases.

PHOTO : Linear lesions in lichen planus.

PHOTO : Lichen planus on the flexor surface of the wrist and the forearm.

PHOTO : Hyperpigmented confluent papules of lichen planus on the shins.

PHOTO : Widespread eruption of lichen planus on the abdomen.

PHOTO : Oral lichen planus, seen as lacy streaks on the buccal mucosa.

PHOTO : Lichen planus presenting as shiny papules on the glans penis.

PHOTO : Lichen planus of the nails, with characteristic longitudinal grooving of the nail plates.

PHOTO : Histopathology of lichen planus. A dense, band-like inflammatory infiltrate obscures the

PHOTO : saw-toothed outline of the dermoepidermal junction. (Hematoxylin-eosin stain, x 10) REFERENCES (1)Beer WE, Machn D. The seasonal incidence of lichen planus. Trans St Johns Hosp Dermatol Soc 1968;54:69-72. (2)Lowe NJ, Cudworth AG, Woodrow JC. HL-A antigens in lichen planus. Br J Dermatol 1976;95:169-71. (3)Halevy S, Zamir R, Gazit E, Feuerman EJ. HLA system in relation to carbohydrate metabolism in lichen planus. Br J Dermatol 1979;100:683-6. (4)Saurat JH, Lemarchand F, Hors J, Nunez-Roldan A, Gluckman E, Dausset J. HLA markers and lymphocytotoxins in lichen planus. Arch Dermatol 1977;113:1719-20. (5)Copeman PW, Tan RS, Timlin D, Samman PD. Familial lichen planus. Another disease or a distinct people? Br J Dermatol 1978;98:573-7. (6)Mahood JM. Familial lichen planus. A report of nine cases from four families with a brief review of the literature. Arch Dermatol 1983;119:292-4. (7)Hellier FF. Familial lichen planus: is it significant evidence of infectivity? 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