Differential diagnosis of localized ACLE

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The diseases, which we may consider in the differential diagnosis with localized ACLE, are acne rosacea, contact dermatitis and photodermatitis, seborrheic dermatitis, dermatomyositis, erysipelas, and delusion of lupus.

2.3.1. Acne rosacea vs ACLE

In its early stages, rosacea may present with a purely erythematous rash on the malar areas that can be very similar to ACLE. The rash may be triggered or aggravated by heat, cold, emotions, and by the ingestion of hot drinks, alcohol, and spicy foods.

Differentiating early rosacea from ACLE only on the basis of the dermatologic evaluation may be very difficult, and therefore the clinical background has to be evaluated because ACLE patients almost always have an active systemic disease.

Over time, a diffuse network of telangiectases may present on the erythematous background, which is characteristic of acne rosacea: nonetheless in patients with SLE who have long been treated with systemic steroids, the atrophy of the skin overlying the malar areas may lead to the appearance of a similar network of telangiectases, and therefore the clinical background remains an essential feature for the differential diagnosis.

In advanced stages of acne rosacea, papules and pustules appear, which are never observed in ACLE, and at this stage clinical differentiation is possible (Fig. 1).

2.3.2. Contact dermatitis vs ACLE

A contact dermatitis of the face may be caused by cosmetics, chemical substances, or plants.

The rash has an acute onset, causes itching, and presents with erythema, vesciculation, oozing, and weeping. Any part of the face may be involved depending on the pattern of exposure to the sen-sitizer (Fig. 2). In severe acute cases, the differentiation with ACLE is easy, but mild subacute cases, in which vesiculation and itching are not relevant, may sometimes create some suspicion.

In such cases, the histology of spongiotic dermatitis and a negative DIF allow for clinical differentiation.

2.3.3. Photodermatitis vs ACLE Drugs or other chemical substances may act as photosensitizers and induce a phototoxic or—in predisposed individuals—a photoallergic reaction resulting in a facial rash resembling ACLE.

The list of possible photosensitizers is very long, comprising many currently used drugs like

Papules And Pustules Rosacea
Figure l. Rosacea: malar erythema with papules and pustules.
Localized Contact Dermatitis Images
Figure 2. Contact dermatitis: acute eruption with a butterfly distribution caused by cosmetic application.

sulfonamides, sulfonylureas, tetracyclines, nalidixic acid, thiazides, non-steroidal anti-inflammatory drugs like piroxicam and ketoprofen, chlorproma-zine, and many others.

Some of these drugs may be frequently prescribed for the treatment of SLE, and considering that some of the patients are not compliant and do not adhere to a strict sun avoidance, the possibility of a photodermatitis has to be kept in mind.

The onset is generally acute, hours (phototoxic reaction) or few days (photoallergic reaction) after ultraviolet exposure, and besides the face, other photoexposed areas may be involved as well, like the dorsa of the hands and feet or the ears, which are generally spared in ACLE, thus allowing for the differentiation. When necessary, histologic examination will reveal a spongiotic dermatitis in photoallergic drug eruptions or vacuolated kera-tinocytes (sunburn cells) and dyskeratosis in a phototoxic reaction (Gilchrest et al., 1981).

2.3.4. Seborrheic dermatitis vs ACLE Seborrheic dermatitis is a very common cutaneous disease presenting as erythemato-squamous plaques, generally located on the face, scalp, presternal area, interscapular region, and occasionally the skin folds. The scales have a characteristic yellowish, non-adherent, greasy appearance. The distribution of the dermatosis and the peculiar scaling generally allow for an easy differentiation from ACLE.

Moreover, in the case of facial involvement, se-borrheic dermatitis frequently affects the naso-labial folds that are—as a rule—spared in ACLE.

In rare instances, the localization on the malar areas and the paucity of scaling may induce some suspicion (Fig. 3), but in any case the plaques tend to have a rather rough and oily surface, which is never encountered in ACLE.

2.3.5. Dermatomyositis vs ACLE

The most frequent initial cutaneous manifestation of dermatomyositis consists of a photosensitive erythematous violaceous eruption (Parodi et al., 2002). When localized exclusively to the face, this rash can be very similar to ACLE (Fig. 4), sharing the same histologic features of an interface dermatitis.

In most of the cases, dermatomyositis patients do not have a sufficient number of clinical and immunological criteria for being classified as SLE, as we would expect in the presence of ACLE.

Differentiation is easier when dermatomyositis-specific cutaneous manifestations (Gottron' papules (Fig. 5), Gottron's sign or the upper eyelid heliotrope rash) are present, if the patient has any clinical evidence of myositis or has any dermatomyositis-specific autoantibodies (anti-Mi-2, anti-synthetases, anti-SRP) (Ghirardello et al., 2005).

2.3.6. Erysipelas vs ACLE Streptococcal infection of the skin may manifest as a superficial cellulitis, appearing as a bright red,

Seborrheic Dermatitis Images Eyebrow
Figure 3. Seborrheic dermatitis: erythematous eruption with a fine yellowish scaling extending to the malar area, the glabella and the eyebrows.
Dermatomyositis Eczema
Figure 4. Dermatomyositis: violaceous erythema on the face resembling ACLE.

edematous plaque with sharply demarcated, elevated, advancing borders. The face is commonly involved with a predilection for the bridge of the nose and the extension to one or both cheeks. The onset is abrupt, with fever and chills. Erysipelas occurs most commonly in children or elderly patients, and has therefore a different age distribution than SLE.

Erysipelas can be considered in the differential diagnosis with ACLE in the case of a bilateral

Gottron Sign Dermatomyositis
Figure 5. Dermatomyositis: Gottron's papules on the dorsal surface of the interphalangeal and metacarpophalangeal joints.

symmetrical involvement of the butterfly area, but the sharp margins, the rapid peripheral extension, the abrupt onset are differential criteria. In the case of erysipelas arising in a SLE patient, the finding of a leukocytosis might be another important element to consider in the differential diagnosis with ACLE.

2.3.7. Delusion of lupus vs ACLE Delusional beliefs of having a butterfly rash occasionally induce some otherwise healthy subjects to ask for a rheumatological consultation (Fig. 6). In these cases, the differential diagnosis is easier than convincing the patient and sometimes the relatives that share the same delusional beliefs.

2.4. Differential diagnosis of generalized ACLE

The diseases, which we may consider in the differential diagnosis with generalized ACLE are mor-billiform drug reactions and erythema multiforme.

2.4.1. Morbilliform drug reactions vs generalized ACLE

Drug reactions with cutaneous manifestations occur in approximately 2.2% of inpatients according to the Boston Collaborative Drug Surveillance Program (Bigby et al., 1986) and an estimate of the overall reaction rate per course of drug therapy is around 3/1000.

Malar Rash Differential
Figure 6. Delusion of lupus: slight erythema on the malar areas in a perfectly healthy subject with delusional beliefs.

Antibiotics are the most frequent culprit drug, with a reaction rate as high as 8% (Bigby, 2001) and an average latency of around 1 week from the drug administration. The exanthematous pattern is the most frequently observed.

The diagnostic problem arises in a SLE patient who develops a morbilliform drug reaction, which the clinician has to differentiate from generalized ACLE.

In the case of a drug reaction the malar rash is not necessarily present, the distribution is wider than in generalized ACLE with involvement on non-sun exposed areas, the palms and soles; the rash may be unrelated to SLE activity, and there is a history of a drug administration 1-2 weeks before the onset. The biopsy examination may reveal eosinophils in the inflammatory infiltrate as a distinctive feature.

2.4.2. Erythema multiforme vs generalized ACLE

Erythema multiforme is a reaction pattern induced by a variety of stimuli, mainly infections (Herpes simplex, Mycoplasma pneumoniae, and streptococ-cal infections) and drugs. Three form of erythema multiforme can be recognized according to the extent of cutaneous and mucosal involvement: of these, erythema multiforme minor can sometimes be considered in the differential diagnosis with generalized ACLE.

The initial manifestations are round erythema-tous papules, spreading over the extensor surface of the limbs with a symmetrical distribution and can be differentiated from generalized ACLE because of the predominant involvement of the extremities (including palms and soles) and the subsequent spread in a centripetal manner (Fig. 7). Moreover, an isomorphic response may be observed, which is not the case of ACLE.

Over some hours or a few days, the cutaneous lesions enlarge with possible coalescence, and may evolve toward the formation of concentric zones of different colors, thus giving rise to the characteristic 'iris' or 'target lesion' that cannot be confused with generalized ACLE (Fig. 8).

Erythema multiforme may develop in SLE patients, and in these cases the rash is not necessarily related to disease activity. However, if asked, patients may recall an infection or drug administration 1-4 weeks before the onset.

The histopathology of early erythema multiforme lesions is characterized by a lymphocytic infiltrate around the upper dermal vessels, hydropic degeneration and necrosis of basal keratinocytes. The presence of dyskeratotic cells, the inflammatory

Sle Generalized Rash

Figure 7. Erythema multiforme: SLE patient with a widespread, non-photodistributed, erythemato-maculo-papular eruption. The characteristic "iris" or "target" lesions are not evident in the early phases of the rash.

infiltrate sparing the appendages, the absence of hyperkeratosis and epidermal atrophy may be some important differential features.

DIF: IgM and C3 around blood vessels in the superficial dermis and C3 along the dermo-epidermal junction can be present in erythema multiforme as compared to the lesional lupus band test observed in SLE. In those cases of erythema multiforme occurring in a SLE patient, the presence of a non-lesional lupus band test can be superimposed, and therefore DIF is not very helpful in differential diagnosis.

3. Subacute cutaneous lupus erythematosus

3.1. Dermatologic features

SCLE has been originally described as a recurring, superficial, non-scarring type of CLE, occurring in a characteristic distribution on the face, upper part of the trunk, and extensor surfaces of the arms with sparing the inner aspects of the arms and the lateral part of the trunk (Gilliam and Sontheimer, 1981).

Hyperkeratosis may be very prominent (psoriasi-form SCLE) but scales are never as adherent or as thick as in CCLE; moreover SCLE lesions, though

Figure 7. Erythema multiforme: SLE patient with a widespread, non-photodistributed, erythemato-maculo-papular eruption. The characteristic "iris" or "target" lesions are not evident in the early phases of the rash.

Pictures Target Lesions
Figure S. Erythema multiforme: characteristic "iris" or "target" lesion.

persistent for several months, are never as indurated as in CCLE, do not tend to develop scarring and heal with a grayish hypopigmentation and eventually some telangiectases.

Two possible SCLE patterns have been identified: a papulosquamous pattern with psoriasiform lesions that may merge to form wide plaques, and an annular-polycyclic pattern, in which lesions undergo central resolution while extending peripherally to form annular elements that may coalesce producing polycyclic, gyrate configurations. Photosensitivity occurs in the majority of SCLE patients.

The histology shows an interface dermatitis as in other LE-specific cutaneous manifestations, almost indistinguishable from CCLE: the most important difference is the inflammatory infiltrate, which is more sparse and superficial in SCLE and denser and deeper in CCLE (Bangert et al., 1984).

The DIF study of the SCLE lesions generally shows the deposition of immunoglobulins and complement components along the dermo-epidermal junction, and in some cases a granular IgG deposition within the epidermis, due to anti-SSA auto-antibodies (Nieboer et al., 1988).

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