Other laboratory features

Other laboratory abnormalities have been reported in SCLE patients at various rates in different studies (Sontheimer, 1989). Those include: elevated erythrocyte sedimentation rates (15-60%), elevated gamma globulin levels (30-50%), hypo-complementemia (15-25%), leukopenia (20-50%), anemia (5-50%) thrombocytopenia (0-40%) rheumatoid factor (35-50%), circulating immune complexes (40-60%) and positive LE cell prep (10-75%).

6. Differential diagnosis

During the early phase of lesions there can be difficulty in distinguishing SCLE from early classical discoid LE lesions before the typical follicular changes and atrophic scarring of discoid LE have appeared. Typically, the carpet tack sign that is a characteristic of discoid LE lesions is not seen and SCLE lesions. (The carpet tack sign is the presence of punctate spikes present on the underside of scale that has been physically removed from the surface of lesions. These small spikes represent the physical manifestations of the follicular hyperkeratosis characteristic of discoid LE lesions on biopsy.) In addition, it has been noted that the presence of induration can serve to help distinguish early discoid LE lesions from SCLE lesions (David-Bajar et al., 1992). The greater depth of the dermal inflammatory infiltrate in discoid LE lesions that can extend even into the subcutaneous layer is thought to be responsible for this induration that is not seen with the more superficial pattern of dermal inflammatory infiltrate that is typical of SCLE.

Differential diagnostic considerations can be different for fully developed annular and pap-ulosquamous SCLE lesions. These issues have been discussed elsewhere (Costner et al., 2004) and are summarized in Table 3.

Annular SCLE lesions in Caucasians have a tendency to become depigmented in their inactive centeral areas resulting from damage to the pigment cell compartment that occurs as a result of the interface dermatitis that is seen in this setting. However, other types of cutaneous annular erythema reactions show either postinflammatory hyperpigmentation at the inactive center of lesions or no pigmentary disturbance at all.

It has been the author's experience that cutaneous dermatomyositis is the skin disease that is most frequently confused by practitioners (including at times even experienced dermatologists) with non-scarring forms of cutaneous LE such as SCLE and acute cutaneous LE. Acute cutaneous

Table 3

Differential diagnosis of idiopathic SCLE

Annular SCLE Tinea incognito Granuloma annulare Erythema multiforme/Rowell's syndrome Erythema annular centrifugum Erythema gyratum repans

Papulosquamous SCLE Cutaneous dermatomyositis Psoriasis

Polymorphous light eruption Pityriasis rubra pilaris Crusted scabies Seborrheic dermatitis Nummular eczema Contact dermatitis Cutaneous T-cell lymphoma

LE is more easily distinguished from cutaneous dermatomyositis due to the frequent presence in acute cutaneous LE patients of overt clinical and laboratory features of systemic LE. The real challenge in distinguishing SCLE from cutaneous dermatomyositis is when the cutaneous dermatomyositis occurs for prolonged periods of time in the absence of muscle weakness (i.e., clinically amyopathic dermatomyositis).

Clinically amyopathic dermatomyositis is a subset of the idiopathic inflammatory myopathies disease spectrum in which the hallmark cutaneous manifestations of dermatomyositis are present for 6 months or longer in the absence of clinically significant muscle weakness (Sontheimer, 2002, 2004b; Sontheimer et al., 2004). The histo-pathological and immunopathological findings in the early course of SCLE and cutaneous dermatomyositis can be quite similar if not indistinguishable. Adding to the confusion with SCLE, in the majority of cases clinically amyopathic dermatomyositis is associated with cutaneous pho-tosensitivity and the production of antinuclear antibodies.

However, when cutaneous LE and cutaneous dermatomyositis become fully expressed clinically there are morphological and regional anatomical differences that can make the distinction between these two entities quite straightforward:

• SCLE only rarely affects the upper eyelids and periorbital areas that are especially targeted by dermatomyositis (i.e., heliotrope erythema).

• SCLE only rarely affects the skin over the bony prominence such as knuckles, elbows, knees, and greater trochanteric area of the lateral proximal thighs that are typically affected in dermatomyositis.

• Gottron's papules and grossly visible finger nailfold telangiectasias do not occur in SCLE to the extent and prominence that they are seen in cutaneous dermatomyositis.

• SCLE typically does not itch while cutaneous dermatomyositis typically itches severely, sometimes with a burning quality. The pruritus of dermatomyositis can be especially severe in the scalp and at night, often to the point of disturbing sleep.

• Poik"ilodermatous skin changes result much more commonly from cutaneous dermato-myositis than cutaneous LE including SCLE.

• While anti-Ro/SS-A antibodies can occasionally be seen in dermatomyositis patients they are typically present in a large majority of SCLE patients.

Some might argue that drug-induced SCLE should be discussed when considering the differential diagnosis of SCLE. While it is quite important clinically to recognize when a drug is precipitating or exacerbating SCLE skin lesions, the author personally considers drug-exposure as another type of environmental stimulus, much like ultraviolet light, that can precipitate or exacerbate SCLE in an immunogenetically predisposed individual.

7. Treatment

The management of patients with new-onset SCLE lesions should include evaluation to rule out underlying systemic disease at the time of diagnosis, then again at 6-12 month intervals, unless the patient develops symptoms that dictate an earlier reassessment. The initial evaluation should include a history, including a careful medication history to rule out drug-induced SCLE (see above), and a review of systems and physical exam to elicit symptoms and signs of underlying systemic disease (i.e., arthritis, serositis, CNS disease, renal disease). Initial laboratory evaluation should include, at the minimum, a complete blood count, platelet count, erythrocyte sedimentation rate, urinalysis, and blood chemistry profile. Additional determinations that can be of help include complement levels (C3, C4, CH50) as well as dsDNA and Sm autoantibodies.

The initial management of all SCLE patients should include education regarding protection from sunlight and artificial sources of ultraviolet light and the avoidance if possible of potentially provocative photosensitizing drugs such as those indicated in Table 1. With regard to specific medical therapy, local measures should be maximized first and then systemic agents used if significant disease activity continues.

7.1. Protection from ultraviolet light

Issues relating to photoprotection in LE patients have been discussed elsewhere in depth by the author (Ting and Sontheimer, 2001).

7.1.1. Physical protection Patients should be advised to avoid direct sun exposure, particularly during the midday hours and during the summer months when the UV component of sunlight is least attenuated by the atmosphere. Tightly woven clothing and hats should be worn in conjunction with broad-spectrum sunscreens to achieve maximal shielding from sunlight. The use of broad-brimmed hats should be encouraged. Several clothing lines offering maximized protection from UV light are currently being marketed. UV light blocking films can be applied to home and automobile windows. Plastic/acrylic shields can be placed over fluorescent light tubes to block the small amount of UVB and UVA radiation that can leak from such sources.

7.1.2. Chemical sunscreens Patients should select broad-spectrum sunscreens that contain agents that block UVB with a sun protection factor (SPF) of 30 or greater. Under everyday usage conditions, the actual SPF of the product is much less than the advertised SPF. This is due mainly to the fact that patients tend to use much less of the product on their skin than is used during the initial laboratory determination of the SPF value for the product. In the USA, preparations containing Parsol 1789/avobenzone and zinc oxide provide the broadest degree of UVA protection, and such products can have added value in SCLE patients. Sunscreen products available in other countries containing the most effective chemical UVA blocker, mexoryl SX, are not yet available in the US (mexoryl SX appears to be more resistant to photodegradation than Parsol 1789/avobenzone). Products should also be selected that are most resistant to being washed off by sweating or bathing. Sunscreens should be applied at least 30min before sun exposure and reapplied after bathing or appreciable perspiration.

Opaque corrective camouflage cosmetic products (e.g., Dermablend, Covermark) are designed to optimally conceal pigmentary changes and scarring. These products offer the dual benefit of being highly effective physical sunscreens as well as aesthetically pleasing cosmetic masking agents for patients suffering psychologically from chronic, disfiguring skin disease as a result of cutaneous LE (Kaye et al., 1991). The proper use of such products can improve the quality of life of patients (Boehncke et al., 2002).

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