A 32-year-old woman presents with an itchy rash that began 3 months ago. She has a history of anxiety but otherwise no known medical conditions. She has tried over-the-counter hydrocortisone cream to treat the rash, finding some relief from the itchiness, but the rash continues to spread. She has no known allergies and has not changed her skin care products or medications. On examination, the patient has dark purple and gray flat-topped papules with fine gray-white streaks on her flexural wrists, dorsal hands, elbows, ankles, and dorsal feet.
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Lichen planus (LP) is a relatively common inflammatory dermatosis first discovered in 1869 by Erasmus Wilson,1 although the condition previously was reported as “lichen ruber” by Hebra.1-3 The Greek word leichen refers to tree moss and the Latin word planus means planar, referring to the condition’s characteristic flat-topped appearance.1,3 LP was described further clinically in 1892 and 1895, and its histopathology was first described by Darier in 1909.1
Although LP occurs in people of any ethnic background and both sexes, it is slightly more prevalent in women and is much more common in adults than children.2-5 The incidence of LP is estimated to be less than 1%, and it accounts for up to 1.2% of dermatology referrals.3 However, a form of cutaneous LP, actinic LP, is highly prevalent in tropical regions, such as the Middle East, East Africa, and India.3 Mucosal involvement is present in up to 65% of cases of cutaneous LP and can be the only clinical manifestation in 15% to 35% of patients.2
The etiology of LP is thought to be primarily immune-mediated.2-4 Cytotoxic CD8+ T cells attack basal keratinocytes and CD4+ helper T cells recruit cytokines,2,3 leading to increased levels of interleukin (IL)-1α, IL-6, and IL-8.6 Other inflammatory cytokines involved include tumor necrosis factor-α and interferon-γ.6 In the dermis and epidermis, there are increased numbers of dendritic cells expressing FXIIIa and S-100-positive Langerhans cells.2,7 The skin’s basement membrane is damaged by the CD8+ cell-mediated destruction of basal keratinocytes, which then allows more CD8+ cells to infiltrate and continuously attack basal keratinocytes. This cycle is hypothesized to explain the chronic nature of LP.3
LP is associated with a number of viruses such as hepatitis B virus, human herpesviruses 6 and 7, and varicella zoster.3 LP is linked most widely to hepatitis C virus (HCV) infection.3-5 A meta-analysis has shown that patients with LP are 5 times more likely to test positive for HCV than controls.5 In addition, interferon therapy for HCV is linked to LP; some patients experience improvement of LP lesions while on this treatment and others have disease flares.3,4,8 Several familial cases of LP have been reported, suggesting a genetic predisposition.3,5
Other risk factors include certain medications, such as antimalarial drugs, β-blockers, thiazides, angiotensin-converting enzyme inhibitors, and nonsteroidal anti-inflammatory drugs, all of which can trigger lichenoid eruptions.3,4 Anxiety, depression, and stress also are associated with LP.3 Additional conditions linked to LP include thymomas, primary biliary cirrhosis, multiple sclerosis, primary sclerosing cholangitis, diabetes mellitus, ulcerative colitis, and Laugier–Hunziker syndrome.3,6
Classically, LP lesions are characterized by violaceous, flat-topped papules. The surfaces of these lesions contain fine, white, reticulated lines referred to as Wickham striae. LP commonly appears on the dorsal hands, flexural aspect of wrists and forearms, shins, and presacral area. LP also may be generalized, although this occurs rarely.
A tool used to identify clinical characteristics of cutaneous LP is the 6 Ps: purple, polygonal, planar, pruritic, papules, and plaques.3,4,8 Lesions are often itchy and commonly lead to postinflammatory hyperpigmentation.5 Lesions may display Koebner phenomenon, in which lesions arise on the skin at sites of prior traumatic injury.5 Other clinical variants of LP include actinic, annular, atrophic, bullous, hypertrophic, inverse, linear, and ulcerative LP.2-4,8
Histology of LP characteristically shows compact hyperkeratosis without parakeratosis, wedge-shaped hypergranulosis, basal cell liquefaction, colloid bodies, dense “band-like” inflammatory infiltrate (lymphocytes and histiocytes) in the papillary dermis at the dermoepidermal junction, irregular acanthosis with saw-tooth rete ridges, and pigment incontinence.2,5,6 Lichenoid drug eruptions potentially can be differentiated from idiopathic LP by the presence of eosinophils and/or plasma cells in the infiltrate, focal parakeratosis, focal interruption of the granular layer, and a deep perivascular infiltrate.2
There are no serum or laboratory tests that can be used to diagnose LP. The condition is diagnosed clinically, and, if needed, diagnosis can be confirmed with a punch biopsy.4-6 When LP is suspected, dermoscopy may be used to look for Wickham striae on the surface of the lesions.2 Clinicians also should examine areas commonly affected by LP, including the nails, scalp, genitalia, and oral mucosa.5 Given its strong association with HCV, serum testing for HCV should be considered in patients diagnosed with LP.5
Several conditions must be considered in the differential diagnosis of LP, such as discoid lupus, erythema dyschromicum perstans, pityriasis rosea, psoriasis, secondary syphilis, and other lichenoid dermatoses.4,8 Unlike LP, lichen nitidus tends to appear in younger patients, rarely involves the oral mucosa, and lacks Wickham striae.1,4,5,8 Lichen striatus primarily occurs in younger patients, and the lesions are generally lighter than those of LP, appearing pink, skin colored, or tan, and often occur as a single linear streak of lesions on an extremity.8
Lichenoid drug eruptions are most difficult to differentiate from cutaneous LP because the conditions may appear identical clinically and histologically. Lichenoid drug eruptions potentially may be distinguished from idiopathic LP by the following: generalized and symmetric distribution, photo distribution, lack of Wickham striae, and greater psoriasiform or eczematous morphology.3 Chronic graft-vs-host
disease (GVHD) after stem cell transplantation also can result in lesions identical to idiopathic LP.5,8 In cases of suspected drug eruption or GVHD, medication history and medical history, respectively, could help distinguish these conditions from LP.3
Cutaneous LP can resolve on its own after 1 year, but treatment may help lesions resolve more quickly.4,5 Drug-induced LP must be considered in all cases and suspected offending medications should be withdrawn. The first-line therapy for cutaneous LP is potent topical glucocorticoids such as clobetasol. Additional well-described therapies include intralesional and systemic corticosteroids, oral retinoids such as acitretin, phototherapy, topical calcineurin inhibitors, antimalarial agents, and in treatment-resistant cases, oral immunosuppressive agents (eg, methotrexate, cyclosporine, mycophenolate mofetil, azathioprine).2,4,5,8
The condition of the patient in this case was confirmed via punch biopsy, and she was prescribed topical clobetasol ointment. At her 3-month follow-up visit, the active lesions were resolved for the most part, with some residual postinflammatory hyperpigmentation. ■
Dina Zamil, BS, is a medical student at Baylor College of Medicine, Tara L. Braun, MD, is a resident in the Department of Dermatology at Baylor College of Medicine, and Christopher Rizk, MD, is a dermatologist affiliated with Baylor College of Medicine in
1. Gupta S, Jawanda MK. Oral lichen planus: an update on etiology, pathogenesis, clinical presentation, diagnosis and management. Indian J Dermatol. 2015;60(3):222-229. doi:10.4103/0019-5154.156315
2. Marshman G. Lichen planus. Australas J Dermatol. 1998;39(1):1-11; quiz 12-13. doi:10.1111/j.1440-0960.1998.tb01233.x
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5. Le Cleach L, Chosidow O. Clinical practice. Lichen planus. N Engl J Med. 2012;366(8):723-732. doi:10.1056/NEJMcp1103641
6. Lehman JS, Tollefson MM, Gibson LE. Lichen planus. Int J Dermatol. 2009;48(7):682-694. doi:10.1111/j.1365-4632.2009.04062.x
7. Akasu R, From L, Kahn HJ. Lymphocyte and macrophage subsets in active and inactive lesions of lichen planus. Am J Dermatopathol. 1993;15(3):217-223. doi:10.1097/00000372-199306000-00004
8. Shiohara T, Mizukawa Y. Lichen Planus and Lichenoid Dermatoses. In: Bolognia JL, Schaffer JV, Cerroni L, eds. Dermatology, 4th ed. Elsevier; 2018;11:188-207.