Testing for skin lupus involves looking for characteristic rashes and examining skin samples under a microscope. Common tests include blood tests, skin biopsies, and direct immunofluorescence. Skin manifestations allow doctors to make the diagnosis of cutaneous lupus erythematosus (CLE) which has several different subtypes. The most common skin lupus subtypes are chronic cutaneous lupus erythematosus (CCLE), subacute cutaneous lupus erythematosus (SCLE), and acute cutaneous lupus erythematosus (ACLE).
Looking for Skin Rashes
Doctors will first do a visual inspection looking for rashes characteristic of lupus. Lupus rashes can appear on sun-exposed areas like the face, neck, and arms as well as other locations. The rashes may be flat or raised and can be ring-shaped, scaly, or red. Some rashes cause permanent scarring and hair loss if they damage hair follicles. Images of lupus rashes are shown below:
Some examples of lupus rashes:
– Butterfly rash: Red rash over the cheeks and bridge of nose, resembling a butterfly’s wings. Often appears or worsens with sun exposure.
– Discoid rash: Red, scaly, coin-shaped rashes that can cause scarring and hair loss. More common in African Americans.
– Malar rash: Fixed red rash over the cheeks and nasal bridge. Does not cause scarring.
– Photosensitive rash: Red or purple rash in sun-exposed areas that flares with sun exposure.
– Vasculitis: Purple or red spots due to inflammation of blood vessels under the skin.
– Oral or nasal ulcers: Sores in the mouth or nose.
Who Gets Skin Lupus?
About 70% of people with systemic lupus erythematosus (SLE) will develop some type of skin rash. Skin lupus is more common in women than men. Certain ethnicities are more susceptible like African Americans, Asians, and Hispanics. Skin lupus usually first appears in people ages 20 to 40.
Blood Tests
Doctors will order blood tests looking for autoantibodies characteristic of lupus. Antinuclear antibody (ANA) testing is commonly used to screen for lupus. Around 95% of lupus patients test positive for ANA. However, a positive ANA does not definitively diagnose lupus since many healthy people will have a positive result. If positive, the titer may indicate likelihood of lupus. Higher titers give more weight to a lupus diagnosis.
Specific autoantibodies are more indicative of lupus:
– Anti-double stranded DNA (Anti-dsDNA): Found in 60% of lupus patients, highly specific for SLE diagnosis.
– Anti-Smith (Anti-Sm): Another very specific antibody, positive in about 30% of lupus patients. Strongly linked to kidney involvement.
– Anti-Ro/SSA and anti-La/SSB: Association with skin findings in lupus, like rash and photosensitivity. Positive in 40-70% of cutaneous lupus patients.
Other tests check for low complement levels (C3 and C4), elevated erythrocyte sedimentation rate (ESR), anemia, leukopenia, or thrombocytopenia which can indicate lupus activity. Urinalysis checks for kidney involvement. Doctors may run additional blood tests to rule out other autoimmune and rheumatic diseases.
Blood Test Results in Skin Lupus Subtypes
| Test | Discoid LE | Subacute Cutaneous LE | Acute Cutaneous LE |
|---|---|---|---|
| ANA | Usually negative | Positive in majority | Positive in most |
| Anti-dsDNA | Negative | Variable, may be positive | Variable, may be positive |
| Anti-Sm | Negative | Negative | Negative |
| Anti-Ro/SSA | Positive in 60% | Positive in 70% | Positive in most |
| Anti-La/SSB | Negative | Positive in 15% | Positive in 40% |
| Low complement | Rare | Uncommon | Common |
This table summarizes typical blood test results seen in various skin lupus subtypes. Discoid LE tends to have more negative results while other subtypes have more positive autoantibodies.
Skin Biopsy
Doctors may perform a skin biopsy by taking a small sample of skin in the area of the rash. The skin sample is sent to a pathologist to be examined under a microscope. Findings characteristic of lupus include:
– Interface dermatitis: Inflammatory immune cells gathered around the hair follicles and glands.
– Basement membrane thickening: The bottom layer of the epidermis is thicker than normal.
– Follicular plugging: Keratin accumulates and plugs hair follicles. Can lead to hair loss and scarring.
– Telangiectasias: Dilated small blood vessels in the skin.
– Mucin deposition: Abnormal deposits of mucopolysaccharides in the skin. Shows up as clumps.
It is important for the pathologist to correlate the skin biopsy findings with the clinical context, including the appearance and location of the rashes. Skin biopsies have limitations in diagnosing skin lupus since various other conditions can cause similar changes. But skin biopsy can help support a lupus diagnosis or rule out other diseases.
Direct Immunofluorescence
This special lab test looks for deposition of antibodies and immune complexes in a skin sample. A fresh biopsy of perilesional skin is taken (near the edge of a rash). The tissue is frozen and stained with fluorescent antibodies that bind to deposited immunoglobulins.
Positive DIF findings in lupus patients may include:
– Granular deposits of IgG at the dermal-epidermal junction
– Deposits of IgM, IgA, and/or C3 in a similar pattern
– Glomerular IgM deposits in the superficial vascular plexus
Not all lupus patients will have positive DIF. Testing can be negative in up to 40% of cases. DIF helps support the diagnosis when positive, but cannot rule out skin lupus if negative. It offers additional evidence when evaluating skin rashes of unclear etiology.
Making the Diagnosis
Doctors integrate findings from the history, physical exam, and tests to determine a diagnosis. Diagnostic criteria have been developed to guide the diagnosis of cutaneous lupus erythematosus. Examples include the Gilliam criteria, Kuhn criteria, and some proposed criteria modifications.
The most commonly used are the Gilliam criteria which require:
1. One major criterion: Classic discoid rash, photosensitive rash, nasal/oral mucosal lesions
2. At least one minor criterion: Facial redness/edema, positive ANA, positive DIF, scarring/pigmentary changes, hair loss, oral/nasal lesions
3. No exclusion criteria: Skin graft stabilization, morphea, drug reaction, viral rash, etc.
Diagnosis is made if the patient meets one major and one minor criteria without exclusion criteria. The criteria help differentiate lupus from other skin diseases with similar lesions. However, diagnostic criteria alone cannot conclusively diagnose – clinical judgment from experienced dermatologists remains important.
Treatment
Treatment focuses on managing current skin disease and preventing flares in skin lupus patients. Options include:
– Sun protection: Sunscreen, sun avoidance, protective clothing and hats. A core part of treatment.
– Topical corticosteroids: Applied directly to rashes to reduce inflammation. Mild forms for face and genitals.
– Topical immunomodulators: Topical tacrolimus or pimecrolimus to reduce inflammation.
– Antimalarials: Hydroxychloroquine improves skin lesions and prevents flares.
– Systemic agents: Oral corticosteroids, immunosuppressants, biologics for severe/resistant cases.
Treatment is tailored to the individual based on symptoms, severity, and type of skin lesions. Mild skin disease may respond to topical creams alone, while systemic medications are warranted for extensive involvement. Lifestyle measures like smoking cessation and emotional support also help.
Monitoring and Follow-up
Ongoing monitoring and follow-up care is important in skin lupus patients. Follow-up visits allow evaluation of whether treatment is working and if adjustments are needed. Monitoring aims to:
– Assess activity and progression of skin lesions
– Check for appearance of new or atypical rashes
– Screen for systemic involvement
– Evaluate any medication side effects
– Provide patient education on photoprotection, skin care, and recognizing flare signs
Patients should follow-up twice yearly at minimum when skin disease is stable. More frequent visits, such as every 3 months, are warranted if active skin disease remains uncontrolled. Regular follow-up allows optimization of therapy to improve disease control and quality of life in skin lupus patients.
Prognosis and Complications
With proper treatment, the prognosis for most cutaneous lupus is good. Many patients achieve adequate control of skin manifestations. However, the chronic relapsing nature of lupus means ongoing diligence is required. Stopping medications can lead to flares. Poorly controlled skin disease carries complications:
– Scarring and hair loss: Discoid lesions often scar and scar tissue lacks hair follicles. Scars are permanent.
– Increased photosensitivity: Leads to more rashes, irritation, and limits outdoor activities. Impacts quality of life.
– Skin infections: Open sores from lupus lesions are prone to infection which requires antibiotics.
– Skin cancer: Long term photosensitivity increases melanoma risk. Patients need regular skin checks.
– Joint disease: 10-15% of chronic cutaneous lupus patients develop arthritis. May indicate progression to SLE.
– Kidney disease: Skin lupus can sometimes spread to kidneys as lupus nephritis, detected by urine tests. Requires aggressive immunosuppression.
With attentive treatment guided by an experienced dermatologist, most patients do well long term. But complications highlight the need for ongoing vigilance and follow-up care.
Conclusion
Diagnosing skin lupus involves clinical evaluation of rashes, blood tests for autoantibodies, skin biopsy, and direct immunofluorescence. Characteristic interface dermatitis on biopsy and deposited immunoglobulins on DIF help support the diagnosis. Treatment aims to control current lesions and prevent new flares using sun protection, topical agents, antimalarials, and systemic medications. With an individualized treatment plan and regular follow-up care, prognosis for skin lupus is generally positive. However, complications like scarring, infections, and systemic spread emphasize the need for ongoing monitoring and diligent photoprotection in lupus patients.