Chapter 12 Lichenoid skin eruptions
2. What does “lichenoid” mean?
The term lichenoid has at least three commonly accepted applications/definitions:
• Originally, the term lichenoid referred to a clinical resemblance of such eruptions to lichens (complex organism consisting of a symbiotic relationship between a fungus and an alga).
3. What is the most common lichenoid skin disease?
Lichen planus is a relatively common disorder, accounting for about 1% of all patient visits to dermatology clinics. The disease most often affects middle-aged adults. Although LP is thought to have no consistent gender predilection, some studies have found women to be more often affected than men. A recent meta-analysis regarding the incidence of oral lichen planus found an overall age-standardized prevalence of 1.27% (0.96% in men and 1.57% in women).
Katta R: Lichen planus, Am Fam Physician 61:3319–3324, 2000.
Carrozzo M: How common is oral lichen planus? Evid Based Dent 9:112–113, 2008.
4. What anatomic locations are most often affected by Lichen planus?
LP may affect both the skin and mucosa. Examination of both areas is essential when the diagnosis of LP is suspected. The frequency of involvement for these areas is somewhat controversial. In general, patients with mucosal disease may not demonstrate skin lesions, but 50% or more of patients with cutaneous disease will demonstrate mucosal lesions. Flexural areas, such as the wrists and ankles, are often involved. Other sites of preferential involvement include the neck, buttocks, sacrum, anogenital region, penis, and buccal or vaginal mucosa.
5. Describe the characteristic primary skin lesions of Lichen planus.
LP is a disease characterized by “P-words”:
• Papules
Primary lesions of the skin are 1 to 5 mm, flat-topped, violaceous, shiny papules (Fig. 12-1). While papules are often clustered, individual lesions tend to be discrete, with angulated (polygonal) borders. Wickham’s stria, a lacy white network present on the surface of the papules, is often of great diagnostic value.
6. What are the characteristic oral findings of Lichen planus?
Mucosal lesions of LP differ from cutaneous lesions through demonstration of Wickham’s stria in the absence of a papular component. A white, reticulated, “netlike” pattern is often present upon the buccal mucosa, the tongue, or other mucosal surfaces (Fig. 12-2). Other mucosal forms may be ulcerative. Some experts believe that some cases of oral LP may be associated with mercury-containing dental amalgams, although the evidence is not conclusive, and still others believe this is a separate category of disease, more aptly termed a mercury-associated lichenoid stomatitis.
Figure 12-2. Lichen planus, showing reticulated leukoplakia of the buccal mucosa.
(Courtesy of James E. Fitzpatrick, MD.)
Dissemond J: Oral lichen planus: an overview, J Dermatol Treat 15:136–140, 2004.
Bruce AJ, Rogers RS 3rd: Lichenoid contact stomatitis, Arch Dermatol 140:1524–1525, 2004.
7. Describe the isomorphic response of Lichen planus.
The isomorphic response (Koebner phenomenon) refers to development of new lesions as a response to external trauma. This phenomenon is characteristic of both LP and psoriasis, among other more rare conditions. In LP, linear aggregates of typical papules may be induced by scratching or rubbing (Fig. 12-3).
8. What causes Lichen planus?
The cause of LP is unknown. Etiologic hypotheses include hypersensitivity reactions, viral infection (particularly hepatitis C), or autoimmune mechanisms. Case reports have linked LP to viral hepatitis, neurologic disease, and severe psychic trauma. Other autoimmune diseases such as vitiligo, inflammatory bowel disease, and autoimmune thyroiditis are seen with increased frequency in those with LP. Lichenoid eruptions (otherwise identical to idiopathic LP) may be seen as a reaction to drugs or as a manifestation of graft-versus-host disease following allogeneic bone marrow transplantation. Oral disease and, to a lesser degree, cutaneous LP have been associated with hypersensitivity to dental amalgams. In actuality, most LP occurs in otherwise healthy people without an identifiable cause.
9. What are the less common presentations of Lichen planus?
Nail changes occur in about 10% to 15% of patients and include longitudinal ridging, irregular pitting, nail plate splitting, nail loss, and pterygium formation with severe onychodystrophy, including “20-nail dystrophy” (Fig. 12-4). Desquamative vaginitis may occur. Clinical and histologic variants of LP include annular (Fig. 12-5), hypertrophic, ulcerative, vesiculobullous, follicular, and actinic induced. LP may also involve the scalp, yielding a scarring alopecia known as lichen planopilaris.
10. How is 20-nail dystrophy related to Lichen planus?
The etiology of 20-nail dystrophy is controversial. This destructive nail disorder affects mostly children, and it is not commonly associated with cutaneous lesions. Typically, all nails show excessive longitudinal ridging, with thin, brittle, opalescent nails. While some experts consider LP to be a possible etiology, other studies utilizing nail biopsy have demonstrated a spongiotic pattern of inflammation rather than a lichenoid process. The condition often results in permanent nail loss, and urgent consultation with a nail specialist is indicated.
11. Is Lichen planus associated with systemic diseases?
LP has been associated with numerous disorders, but such relationships often engender controversy. Associated conditions include viral hepatitis, chronic active hepatitis, primary biliary cirrhosis, diabetes mellitus, internal malignancy, and autoimmune or connective tissue disease. The relationship to infection with hepatitis C (HCV) is controversial. The latest metaanalysis concluded that the association exists in some regions (East/Southeast Asia, South America, the Middle East, and Europe) but not in others (North America, South Asia, and Africa). At present, it is recommended that patients with LP be queried about major risks factors (IV drug use or sex with IV drug users) or minor risk factors (history of blood transfusion, male sex, and age 30 to 49 years) and that those with significant risk be screened for HCV antibodies.
12. What is the prognosis of Lichen planus?
The duration of disease activity is related to the site of involvement. Isolated mucosal involvement portends a more chronic course, perhaps lasting decades. Additionally, patients with oral LP are at increased risk of squamous cell carcinoma arising within chronic lesions. Conversely, isolated cutaneous involvement typically resolves spontaneously within 1 to 2 years. Patients with both mucosal and cutaneous lesions typically have an intermediate prognosis. Certain clinical subtypes, such as ulcerative, palmoplantar, and actinic LP, are more persistent and recalcitrant to treatment. Twenty percent of patients may relapse after an initial clearing.
13. What is the primary symptom of Lichen planus?
The pruritus of LP is often intense. Nearly all patients report some itching. Interestingly, the pruritus of LP often maintains a special quality that will induce rubbing, rather than scratching, for relief. Such rubbing may account for the polished appearance of the lesions. If excoriation occurs, new lesions are likely to develop within wounds (Koebnerization).
14. Describe the characteristic histopathologic features of classic Lichen planus.
• The stratum corneum is thickened (hyperkeratotic), but is largely devoid of retained keratinocytic nuclei (essentially no parakeratosis).
15. How is lichen planus treated?
Topical corticosteroids and oral antihistamines are used to ameliorate the pruritus in mild cases. Hypertrophic lesions may not respond to topical treatment and instead may require intralesional corticosteroids. The optimal treatment of severe disease is difficult to determine since the studies regarding treatment have been primarily anecdotal or consist of small series. The most commonly used treatment is systemic corticosteroids, but variable degrees of success have also been reported with topical calcineurin inhibitors (tacrolimus and pimectrolims), psoralen plus ultraviolet A (PUVA) light therapy, narrow-band ultraviolet B (UVB) light therapy, oral retinoids (isotretinoin and acitretin), griseofulvin, methotrexate, cyclosporine, sulfasalazine, and thalidomide.
16. What conditions enter the differential diagnosis of an “Lichen planus-like” eruption?
Lichenoid drug eruptions may be indistinguishable from idiopathic LP. Any exogenous ingestant, or rarely a topical chemical, may be causative. Common etiologic agents are listed in Table 12-1. Other potables, such as alcoholic liqueurs containing gold particles, have been implicated in lichenoid eruptions. Contact with certain chemicals, particularly those involved with photodeveloping, may result in a lichenoid contact dermatitis. Clues suggesting a lichenoid drug eruption include an atypical distribution or lack of mucosal involvement. Histopathologic clues to a drug-induced eruption include significant parakeratosis and eosinophils within the inflammatory infiltrate.
Table 12-1. Common Etiologic Drug Classes in LP-like Drug Eruptions
| Antihypertensives Beta-blockers ACE inhibitors Thiazides Furosemide Methyldopa Antimicrobials Acyclovir Isoniazid Tetracyclines Antiinflammatory agents Nonsteroidal anti-inflammatory drugs Gold salts Sulfones |
Antimalarials Chloroquine Quinacrine Anticonvulsants Carbamazepine Phenytoin Neurologic agents Benzodiazepines Phenothiazines Lipid-lowering agents Lovastatin Fluvastatin Biologic response modifiers Tumor necrosis factor α antagonists (infliximab, etanercept, adalimumab) Imatinib mesylate |
Miscellaneous Sulfonylureas Chlorpropamide Allopurinol Penicillamine Sildenafil Misoprostol |
Ellgehausen P, Elsner P, Burg G: Drug-induced lichen planus, Clin Dermatol 16:325–332, 1998.
17. Are Lichen planus and systemic lupus erythematosus related?
18. Are Lichen planus and bullous pemphigoid related?
Lichen planus pemphigoides is a rare skin disease that presents with overlapping features of LP and bullous pemphigoid. It is characterized by bullous lesions arising on lichen planus–like papules and also upon uninvolved skin. While the condition may arise de novo, particularly in children, it may also be induced by medications including: cinnarizine, captopril, ramipril, simvastatin, PUVA, antituberculous medications, and some Chinese herbs.
19. Why is graft-versus-host disease a consideration in Lichen planus-like eruptions?
Graft-versus-host disease (GVHD) is a complication of allogeneic bone marrow transplantation. In GVHD, the immune effector cells of the donor bone marrow (the “graft”) react against antigens of the recipient tissues (the “host”). The resultant eruption may be indistinguishable, both clinically and histopathologically, from that of LP. Lichenoid GVHD reaction is often more generalized than is classic LP, and the history would certainly be suggestive. GVHD resulting from solid-organ transplantation is exquisitely rare.
Key Points: Lichen Planus
2. Lichen planus, in addition to affecting skin, can also affect the oral or vaginal mucosal surface, nails, or hair.
20. Describe the primary lesion of lichen nitidus.
21. What are the other clinical features of lichen nitidus?
LN is uncommon relative to LP. It too has no gender, age, or race predilection. It may affect any age but it is more common in children and young adults. The eruption is typically idiopathic, chronic, and, fortunately, asymptomatic. An isomorphic response may be demonstrated. The disease is most often self-limited and resolves spontaneously over months to years. There are no well recognized disease associations. Rarely, medications have been implicated. Response to treatment, generally limited to mild topical corticosteroids, is poor. Reassurance and education are often the best therapy.
22. Does lichen nitidus demonstrate a lichenoid infiltrate upon biopsy?
No. While LN appears “lichenoid” clinically, the histopathologic findings are granulomatous in nature. Typically, the epidermis demonstrates central atrophy, while peripheral epidermal rete ridges extend into the papillary dermis in “clawlike” fashion, surrounding a granulomatous aggregate of lymphocytes and histiocytes.
23. What is lichen striatus?
Lichen striatus is an uncommon idiopathic dermatosis that presents as a linear plaque, most often on the extremity or neck of a child or, less commonly, an adult. The condition consists of a coalescent group of flesh or rose-colored lichenoid papules (Fig. 12-7). The resultant linear plaque may form a band several centimeters wide and may course the entire length of the extremity.
25. What is lichen simplex chronicus?
Lichen simplex chronicus (LSC) is not a disease but rather a reaction of the skin to chronic friction from rubbing or scratching. LSC may be superimposed upon normal skin, but it is often a secondary condition of chronically inflamed skin. The clinical appearance, termed lichenification, is characteristic, regardless of the underlying etiology. Relative thickening of the skin, with accentuation of the normal skin lines, is typical. Closely set lichenoid papules may be discerned at the periphery. Frequently, the lichenified plaque maintains a dusky violaceous hue.
26. How is lichen simplex chronicus treated?
LSC is a self-perpetuating dermatosis, and it will persist until the initiating stimulus is eliminated. Interruption of the “itch-scratch cycle” is requisite to resolution. A short course of medium- or high-potency topical corticosteroids is typically employed. Covering the plaque is often important, as this acts as a physical barrier to continued frictional trauma and also acts as an occlusive adjunct for the topical preparation. Patients who express insight into the cause of their condition fare better. Resultant postinflammatory dyspigmentation may last for years, even after the changes of lichenification have resolved.
