Systemic lupus erythematosus in Adult
Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that affects the skin and internal organs and is characterized by pathogenic circulating autoantibodies. Sex and ethnicity are the strongest risk factors for developing SLE, with a 6:1 female-to-male ratio, and black women demonstrating a fourfold higher incidence when compared to whites. Women of child-bearing potential are most commonly affected.
The etiology of SLE is poorly understood, but there is a strong association with autoantibodies and SLE. For example, even though the autoantibodies are not organ specific, only certain organs in a given patient demonstrate end-organ damage. It is hypothesized that a complex interplay between genetic proclivity and environmental influences leads to a perpetuated autoimmune response. Autoantibodies play significant roles in the diagnosis, management, and prognosis of SLE. They are as follows:
- Anti-dsDNA – Highly specific for SLE. Rising levels correlate with increased SLE activity and an increased risk for SLE nephritis. Seen in approximately 55%-65% of SLE patients.
- Anti-Sm – Highly specific for SLE. Seen in approximately 25%-30% of SLE patients. Considerable diagnostic value, but levels do not correlate with disease activity.
- Anti-RNP – Highly specific for SLE. Seen in approximately 5% of SLE patients.
- ANA – Highly sensitive for SLE. Seen in approximately 99% of SLE patients. In other words, it is very rare for an SLE individual to have a negative ANA. Considerable screening value, but levels do not correlate with disease activity.
- Anti-histones – Highly specific for drug-induced SLE.
In regard to classifying cutaneous lesions, specific and nonspecific types exist. Within the group of specific lesions, there are 3 main subtypes based on chronicity, association with SLE, and location/depth of inflammatory infiltrate. They are as follows:
- Acute cutaneous lupus erythematosus (ACLE)
- Transient cutaneous findings typified by malar erythema without scarring
- Strongly associated with systemic findings
- Inflammatory infiltrate seen in the superficial dermis on biopsy
- Subacute cutaneous lupus erythematosus (SCLE)
- Photosensitive cutaneous eruption lasting longer than ACLE but without scarring
- 10%-15% of patients go on to have systemic findings
- Inflammatory infiltrate seen in the upper dermis on biopsy
- Chronic cutaneous lupus erythematosus (CCLE)
- Also known as discoid lupus erythematosus (DLE)
- Chronic discoid lesions with permanent disfiguring scars
- 5%-10% of patients go on to develop systemic findings
- Significant inflammatory infiltrate seen in superficial and deep dermis as well as prominent involvement of the adnexal structures on biopsy
Related topics: Oral lupus erythematosus, Tumid lupus erythematosus
M32.9 – Systemic lupus erythematosus, unspecified
55464009 – Systemic lupus erythematosus
- Drug-induced SLE
- Dermatomyositis – Characteristic heliotrope rash (violaceous plaques surrounding eyes), photodistributed cutaneous eruption, and nailfold changes. Look for elevated serum CK levels and proximal symmetric extremity weakness.
- Rosacea – ANA negative.
- Stevens-Johnson syndrome – Characteristic target lesions, prominent systemic symptoms, but ANA and DIF negative.
- Antiphospholipid antibody syndrome / lupus anticoagulant – Can overlap with SLE; associated with recurrent thromboses and spontaneous abortions, elevated PT time.
- Polymorphous light eruption (PMLE) – Most lesions resolve within several days; skin lesions are located primarily on sun-exposed areas (SLE can occur on sun-exposed and sun-protected areas). Note that previous studies have shown that up to 19% of patients with PMLE can be ANA positive. Hence, an ANA alone may not be sufficient in differentiating PMLE from SLE.
- Phototoxic / photoallergic drug eruptions
- CREST syndrome – Can have overlap with dermatomyositis. Refers to a subset of patients with limited scleroderma.
- Seborrheic dermatitis – No systemic findings. Erythema and scale in sebaceous distribution.
- Systemic amyloidosis
- Contact dermatitis
- Pityriasis rubra pilaris
- Scleroderma – Check for anticentromere antibodies and anti-Scl-70 antibodies. Typified by sclerotic changes in skin not seen in dermatomyositis.
- Graft-versus-host disease – Occurs after allogeneic stem-cell transplantation
- Mixed connective tissue disease – Check for anti-U1RNP antibody. Most patients are positive for this in mixed connective tissue disease.
- Generalized morphea – Asymmetric induration, no Raynaud's phenomenon, no systemic involvement.
- Polymyositis – Without cutaneous findings.
- Acute lesions of erythropoietic protoporphyria may have similar locations, especially on the dorsum of the hands, but usually there is no weakness.
- Tinea faciei – Check potassium hydroxide (KOH); will also be ANA negative.
- Chilblains (perniosis)