Key Terms
Lichen Planus
Annular lichen planus
Bullous lichen planus
Hypertrophic lichen planus
Grover Disease
Transient acantholytic dermatosis
Actinic Keratosis
Atrophic actinic keratosis
Hypertrophic actinic keratosis
Pigmented actinic keratosis
Scaly papular disorders include an unrelated admixture of neoplastic and inflammatory disorders characterized by small palpable lesions with variable scale, which are usually smaller than 1 cm in their greatest diameter. Some disorders, such as guttate psoriasis, may contain some lesions larger than 1 cm and would technically be classified as scaly plaques. Some lesions that are typically papular may become exuberant enough (e.g., actinic keratosis) that they are morphologically scaly nodules.
Important History Questions
How long has the lesion(s) been present?
Some of the disorders in this group may appear acutely (e.g., guttate psoriasis, lichen planus); other disorders (e.g., actinic keratoses) appear gradually.
Have you had a similar lesion(s) in the past?
A “yes” answer favors some disorders with a genetic basis, such as psoriasis or actinic keratoses, that tend to occur in the background of chronic sun damage.
Do any of your immediate relatives have psoriasis?
A “yes” answer indicates a genetic predisposition for the development of psoriasis.
Have you had any previous pre–skin cancers or skin cancers?
A positive history of a previous pre–skin cancer or skin cancer indicates that the patient has had enough sun damage to promote the development of pre–skin cancers (e.g., actinic keratoses), squamous cell carcinoma in situ, and squamous cell carcinoma.
How are you treating your skin condition?
Many patients use home-based, over-the-counter (OTC), or prescription remedies that can alter the appearance of the condition.
Are you taking any medications?
Some medications may precipitate or aggravate some of the disorders discussed in this chapter. For example, psoriasis can be worsened by beta blockers, lithium, and terbinafine. Lichen planus can be mimicked by numerous medications (e.g., thiazide diuretics).
Have you had a recent illness?
This is important because streptococcal infections frequently precipitate episodes of guttate psoriasis, and lichen planus can be associated with virus-induced hepatitis.
Important Physical Findings
How many lesions are present?
Some of the disorders in this section can be solitary or multiple (e.g., actinic keratosis) or are characteristically multiple (e.g., psoriasis, lichen planus, lichen nitidus).
What is the distribution of the lesions?
Some of the disorders demonstrate a characteristic location. For example, guttate psoriasis usually affects the trunk and proximal extremities.
Is the oral mucosa involved?
Lichen planus frequently involves the oral mucosa, and finding characteristic involvement can be useful in establishing the diagnosis. In contrast, psoriasis only rarely involves the oral cavity and, if present, it is usually confined to the tongue. Actinic keratoses may involve the sun-exposed mucosa of the lower lip (actinic cheilitis) but do not involve the protected oral mucosa.
Are the nails normal or abnormal?
The nails are frequently involved in psoriasis, Darier disease, and occasionally lichen planus, but most of the remaining disorders typically demonstrate normal nails.
Guttate Psoriasis
ICD10 code L40.4
GENETIC DISORDER
Pathogenesis
Psoriasis is a common hereditary disease with a chronic course that primarily affects the skin, with variable involvement of the joints and oral mucosa. The cutaneous manifestations are protean; these include classic plaques (see Chapter 8 ), pustular psoriasis (see Chapter 12 ), erythrodermic psoriasis, and the guttate pattern of psoriasis. Although psoriasis is a genetic disorder, it is generally preceded by a trigger; guttate psoriasis is often the initial manifestation of the psoriatic diathesis. The most common trigger in the guttate variant is streptococcal pharyngitis (63%). Less commonly implicated triggers include a recent life crisis (46%), skin injury, drugs, and exposure to ultraviolet (UV) light.
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Beta blockers (most common)
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Biologic agents (e.g., infliximab)
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Lithium
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Terbinafine
Clinical Features
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Guttate psoriasis can affect any portion of the body; however, it demonstrates a marked predilection for the trunk and proximal extremities ( Fig. 7.1 ).
Fig. 7.1
Typical trunk and proximal extremity distribution of guttate psoriasis. Note the koebnerized lesions on the left upper arm.
(From the Fitzsimons Army Medical Center Collection, Aurora, CO.)
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The primary lesion is manifested by small, pink to reddish papules that typically vary from 2 to 10 mm in size; however, larger lesions can be present. Very early lesions may not yet demonstrate scale ( Fig. 7.2 ), with mature lesions demonstrating variable scale ( Fig. 7.3 ).
Fig. 7.2
Early guttate psoriasis in a young child. In early lesions, the scale is not present or minimal; however, the prominent red color and uniform appearance is strongly suggestive.
(From the William Weston Collection, Aurora, CO.)
Fig. 7.3
Close-up of a patient with developed lesions of guttate psoriasis demonstrating abundant white scale. These lesions are diagnostic and do not require a biopsy.
(From the William Weston Collection, Aurora, CO.)
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The Koebner phenomenon—psoriasis developing at sites of superficial trauma—occurs in about 5% of patients with psoriasis and is especially common during acute flares of guttate psoriasis (see Fig. 7.3 ).
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Nail involvement (see Chapter 25 ) can be present but usually does not occur in early guttate psoriasis, when patients are most likely to present to an urgent care or emergency room setting. If present, it is usually seen as distinct nail pits. Less commonly in guttate psoriasis, the patient may demonstrate yellowish-brown areas of discoloration below the nail (oil spots).
Diagnosis
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There is a clinical presentation of uniform papules with scale that is of an acute onset.
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The presence of the Koebner phenomenon is strongly supportive of the diagnosis.
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The presence of significant nail pitting or oil spots in the nail bed is strongly suggestive of psoriasis.
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There may be a family history; first-degree relatives with psoriasis can be identified in about one-third of patients.
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Some cases may require a 3- or 4-mm punch biopsy of a well-developed lesion, which is more likely diagnostic.
Treatment
The selection of therapy depends on the patient’s age and general health, cost, local availability of specialized treatment facilities, distribution and extent of the lesions, and motivation of the patient.
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In most cases, the treatment of choice is light therapy; the best options are natural sunlight (cheapest), UVB phototherapy, which includes narrow-band UVB, or methoxsalen plus UVA.
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The primary topical option is once- or twice-daily application of topical corticosteroids of varying strengths, depending on the location, severity of disease, and response to therapy.
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For severe or resistant cases, acitretin is a consideration.
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In patients with guttate psoriasis, strongly consider empiric oral antibiotics to eliminate infectious triggers, and carefully review the patient’s medications for potential triggering drugs.
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In the largest study to date (79 patients), 25% of patients went on to develop chronic plaque psoriasis, but the remaining patients did not. There were no known clinical or laboratory findings that could predict the outcome for a given individual.
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Of patients with guttate psoriasis, only 65% were clear or improved at 3 months, and 99% were clear or improved at 12 months.
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Although not evaluated in this study, some patients will have more than one episode of guttate psoriasis.
Lichen Nitidus
ICD10 code L44.1
INTERNAL ETIOLOGY
Pathogenesis
This is a relatively uncommon, self-limited dermatosis of unknown cause that is usually discussed as a papulosquamous disorder in most texts. Although the pathogenesis is understood, occasional patients have associated lichen planus. This association, plus the finding of dead keratinocytes, suggests a host autoimmune response against keratinocytes.
Clinical Features
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Lichen nitidus usually affects children, adolescents, and young adults, but any age group can be affected. It can be found in any ethnic group, but black patients are most commonly affected.
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Patients are typically asymptomatic, but rare patients may complain of mild pruritus.
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Typically, there is a symmetric diffuse eruption that usually affects the trunk and proximal extremities ( Fig. 7.4 ). In males, the genitalia are frequently involved ( Fig. 7.5 ).
Fig. 7.4
Patient with lichen nitidus. Shown are the characteristic uniform symmetric papules, with white scale on the extremities. The large number of lesions is unusual.
(From the Walter Reed Army Medical Center Collection, Washington, DC.)
Fig. 7.5
In males, the genitalia is frequently affected in lichen nitidus.
(From the Fitzsimons Army Medical Center Collection, Aurora, CO.)
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The primary lesion consists of a 1- to 3-mm round papule, with no scale or a small amount of detectable scale. The papules can be skin-colored but are often lighter than the surrounding skin due to the scale.
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Lesions may focally have linear configurations due to superficial minor trauma (Koebner phenomenon; Fig. 7.6 ).
Fig. 7.6
Close-up of lesions demonstrating the Koebner phenomenon. This is a helpful feature for the diagnosis of lichen nitidus.
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Lichen nitidus with focal hemorrhage is a very rare clinical variant.
Diagnosis
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The differential diagnosis includes atypical lichen planus, papular secondary syphilis, papular sarcoidosis, and atypical Langerhans cell histiocytosis.
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Clinical appearance is usually diagnostic, and further testing is not required.
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If secondary syphilis is a clinical consideration (i.e., atypical presentation in a sexually active adolescent or young adult), a rapid plasma reagin (RPR) test or venereal disease research laboratory (VDRL) test is appropriate.
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If papular sarcoidosis is a clinical consideration—that is, the patient has clinical features such as larger lesions, facial lesions, or systemic symptoms—a screening chest x-ray may be indicated.
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A skin biopsy (e.g., shave biopsy, 3-mm punch biopsy) is not usually indicated, but if the presentation is atypical, it is usually diagnostic because the histologic findings are specific.
Treatment
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Reassurance should be given to the patient because this a self-limited, harmless skin disorder.
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A weak topical corticosteroid (1% hydrocortisone) to midstrength topical corticosteroid (0.1% triamcinolone) is recommended if the lesions are pruritic.
Clinical Course
Lichen nitidus typically goes away within weeks but usually months, with some cases lasting as long as 1 year. There are no permanent sequelae, although rare patients may demonstrate residual hyperpigmentation.
Lichen Planus
ICD10 code L43
INTERNAL ETIOLOGY
Pathogenesis
Lichen planus is relatively common, with one epidemiologic study reporting a prevalence of 0.4% in the United States. The cause is not entirely understood, although studies have suggested that it is an autoimmune disease based on histologic findings, immunologic data, and association with other autoimmune diseases. Of interest is the weak association of chronic, ulcerative lichen planus with hepatitis C infection.
Clinical Features
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Lichen planus may occur at any age (average age of onset, 52 years); pediatric cases only account for 2% of cases.
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The primary lesions are intensely pruritic, violaceous, polygonal papules that may demonstrate a fine white lacy appearance on the surface; these are called Wickham striae ( Figs. 7.7 and 7.8 ). Although classified as a papulosquamous disease, the amount of scale is variable and may even be absent.
