Chapter 10: Inflammatory Skin Conditions
Cutaneous Lupus Erythematosus
What is it?
Cutaneous lupus describes a wide range of skin findings that may or may not be seen in association with systemic lupus. The frequency with which patients have or go on to develop systemic lupus varies widely depending on which type of cutaneous lupus they have:
Acute cutaneous lupus is almost always accompanied by systemic lupus (more than 90% of cases) and includes the classic malar (“butterfly”) rash that most people associate with lupus. However, it may also manifest as a more widespread rash of red macules and papules on the trunk and limbs.
Subacute cutaneous lupus presents in a photodistribution (areas exposed to sunlight such as the face, neck and outer arms) and may be scaly and red (similar to psoriasis) or annular (lesions with a red rim with central clearing). Approximately 50% of patients with this form of cutaneous lupus will meet criteria for systemic lupus at some point in their life. Approximately 20-30% of cases are drug-induced, and may be caused by widely prescribed medications such as terbinafine, minocycline and hydrochlorothiazide.
Discoid lupus is a form of chronic cutaneous lupus. Only around 10% of these patients will have systemic lupus. It presents as scaly red plaques on the head and neck, which may scar leaving dyspigmentation and permanent hair loss. Commonly affected areas include inside the ear and on the nose and cheeks.
Neonatal lupus is seen in newborns due to placental transmission of maternal auto-antibodies against Ro, La and/or U1RNP. It is usually present at birth or shortly thereafter. It presents as round, red, scaly plaques typically located on the forehead and around the eyes. It can be associated with internal manifestations including heart block, liver disease and low platelets.
Non-specific skin findings such as photosensitivity, diffuse non-scarring alopecia, Raynaud phenomenon and dilated blood vessels around the nails may all be seen with lupus but are also frequently seen in other connective tissue diseases such as dermatomyositis and systemic sclerosis.
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How is it managed?
A history and physical (focusing on the signs and symptoms of connective tissue disease such as fevers, joint pain, oral ulcers, Raynaud phenomenon, hair loss, photosensitivity, neurologic symptoms) and laboratory work up (such as CBC, renal function, ANA/ENA, double-stranded DNA, complement levels, and skin biopsy) should be performed to investigate for systemic lupus or other autoimmune conditions.
Patients with all forms of cutaneous lupus are photosensitive and need adequate sun protection. Patients with acute cutaneous lupus are usually systemically unwell and should be managed in consultation with a rheumatologist.
Subacute cutaneous lupus is often treated with topical corticosteroids and/or calcineurin inhibitors. Hydroxycloroquine might be added as a systemic treatment.
Localized and mild forms of discoid lupus can often be managed with sun avoidance and topical or intralesional steroids. Topical calcineurin inhibitors may also be used to avoid prolonged use of topical steroids on the face. Extensive, severe or resistant cases can be treated with systemic agents such as hydroxychloroquine and corticosteroids.
What is in the differential diagnosis?
Subacute cutaneous lupus and discoid lupus might be confused with fungal infections or nummular eczema. The malar rash in SLE can be confused with rosacea or seborrheic dermatitis. Dermatomyositis is an autoimmune disease targeting the skin and/or muscle. There is a wide range of potential skin manifestations, many of which are non-specific and overlap with lupus. However, there are several findings which are more specific: the heliotrope sign describes purple discolouration of the eyelids sometimes accompanied by swelling; Gottron’s papules are red to purple flat-topped papules affecting the dorsal hands, especially the skin over the knuckles (MCPs, PIPs and DIPs); capillary loops and drop-out can be seen at the cuticles. In adults, dermatomyositis is often associated with underlying malignancy but not in juvenile dermatomyositis, a distinct variant of this condition peaking at 8 years of age. The juvenile form also differs in that it frequently presents with calcinosis cutis: hard irregular nodules that form on the elbows and knees and may drain chalky material.
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