It is evident that specific immunologic mechanisms control the development of lichen planus (LP). It has been proposed that CD8+ cytotoxic T cells recognize an antigen (currently unknown) associated with the major histocompatibility complex (MHC) class I on lesional keratinocytes and lyse them. Direct immunofluorescence examination of LP shows colloid bodies in the papillary dermis, staining for complement and immunoglobulins, particularly IgM. An irregular band of fibrin is present along the basal layer in most cases. Often there is irregular extension of the fibrin into the underlying papillary dermis.
Annular lesions occur in about 10% of LP cases. Men represent 90% of patients with annular LP. Patients usually have fewer than 10 lesions. Most patients with annular LP are asymptomatic. When itching exists, most patients react to the itching by rubbing rather than scratching. Arcuate groupings of individual papules develop rings. Clustered papules with peripheral extension and central clearing leads to annular lesions too. Male genitalia are involved in 25% of LP cases (partly explained by the Koebner phenomenon) and it may be the only manifestation of the disease. Chronic erosive gingival and genital lesions (genito-gingival syndrome) has been described. Chronic mucosal erosive LP is associated with a risk of squamous cell carcinoma (SCC). Most reports linking the two concern oral LP though. SCC has occurred in the context of hypertrophic LP of the glans penis.
Annular LP is most commonly found on the penis as shown in this patient. Lesions usually have a very narrow rim of activity and a depressed, slightly atrophic, centre hence term annular atrophic lichen planus. Much less often, the margin is wide, and the central area is quite small. Polycyclic figures may be formed. The differential diagnosis includes granuloma annulare. Central hyperpigmentation may be the dominant feature as shown on the glans penis of this patient. LP can cause phimosis. Bullous penile LP has been reported. Actinic lichen planus is frequently annular in shape too.
Histopathology of LP shows a lichenoid reaction pattern characterised by the combination of degeneration of the basal layer of the epidermis and a band like lymphocytic infiltrate obscuring the dermoepidermal junction. A distinct entity termed “annular lichenoid dermatitis of youth” has been described, and is characterized by persistent asymptomatic erythematous macules and round annular patches with a red-brownish border and central hypopigmentation, mostly distributed on the groin and flanks, in children and adolescents. Histopathology reveals lichenoid reaction pattern with necrosis/apoptosis of the keratinocytes limited to the tips of rete ridges. It can affect adult patients too; therefore, the name “annular lichenoid dermatitis” has been proposed.
Although LP is self-limiting, some patients experience relapses and remissions. Potent or very potent topical steroid creams and ointments usually produce remission and remain the treatment of choice for lichen planus in patients with classic and localized disease. Patients should be warned about postinflammatory hyperpigmentation. It can persist for months to years. Circumcision is seriously considered if there is phimosis.
|Potent or very potent topical steroid creams and ointments usually produce remission as shown here and remain the treatment of choice for lichen planus in patients with classic and localized disease.|
This page was last updated in September 2015.