Differentials
Systemic lupus erythematosus (SLE)
SIGNS / SYMPTOMS
Skin manifestations are a common presentation of SLE. The photosensitive malar or butterfly rash is characteristic. This erythematous rash extends from the cheeks over the bridge of the nose, sparing the nasolabial folds. It can be painful and pruritic, usually lasts a few days, heals without scarring, but often recurs after sun exposure.
The diagnosis is made using 2019 criteria recommended by the American College of Rheumatology and the European League Against Rheumatology.[13]
INVESTIGATIONS
High-titer ANA, anti-double-stranded DNA antibodies, and anti-ribonucleoprotein antibodies are strongly suggestive.
Subacute cutaneous lupus erythematosus (SCLE)
SIGNS / SYMPTOMS
SCLE lesions begin as small, erythematous, slightly scaly papules that evolve into either psoriasiform (papulosquamous) or annular forms. The lesions typically have erythematous crusted margins, usually sparing the face and mostly affecting the neck, arms, and upper torso.
Although telangiectasia may be seen, permanent pigment changes and scarring are absent.
INVESTIGATIONS
Findings on skin biopsy are similar to those of DLE, except that basement membrane thickening is generally absent or minimal.
Psoriasis
SIGNS / SYMPTOMS
Lesions are red, inflamed, silvery-white scaly and circumscribed papules and plaques; often affecting the elbows, knees, extensor limbs, and scalp. Psoriatic nails have a pitted surface, onycholysis, and/or hypertrophic (subungual) changes.
INVESTIGATIONS
Skin biopsy findings include intraepidermal spongiform pustules and Munro neutrophilic microabscess within the stratum corneum.
Polymorphous light eruption (PMLE)
SIGNS / SYMPTOMS
Considered an exclusively photo-triggered dermatosis that can express several clinical forms.
PMLE lesions are usually itchy papules, eczematous plaques, or vesicles. They typically develop within 24 hours of sun exposure and there is often associated urticaria.
INVESTIGATIONS
Skin biopsy shows edema in the upper part of the dermis.
Rosacea
SIGNS / SYMPTOMS
Common chronic disorder of the skin characterized by redness, flushing, and other cutaneous findings that often include telangiectasia, papules and/or pustules, rhinophyma, and general inflammation that can resemble acne.
Typically affects the convexities of the central face, including the nose, cheeks, eyelids, and forehead.
INVESTIGATIONS
Skin biopsy shows nonspecific granulomatous or lymphohistiocytic infiltrate. Associated edema, telangiectasia, and sebaceous hyperplasia may also be present.
Lichen planopilaris
SIGNS / SYMPTOMS
Refers to lichen planus of the hair follicles. Presents with alopecia associated with hyperkeratotic papules and perifollicular erythema with scale.
Typical lichen planus lesions affecting skin, nails, and buccal mucosa may also be present.
INVESTIGATIONS
Skin biopsy shows lichenoid lymphocytic infiltrate under the epidermis.
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