Systemic Lupus Erythematosus (SLE) is a chronic autoimmune condition where the body’s immune system mistakenly produces autoantibodies that target and attack its own healthy tissues and organs. This systemic attack can lead to inflammation and damage in nearly any part of the body, including the joints, kidneys, brain, and blood cells. The skin is one of the most frequently affected organ systems, with an estimated 80% of individuals with SLE experiencing some form of skin involvement. This article explores the range of skin issues associated with lupus to clarify how and when blistering can occur.
Common Skin Rashes Associated with Lupus
The majority of skin symptoms that affect people with lupus do not involve the formation of fluid-filled blisters. These common manifestations are classified into three main types of cutaneous lupus based on their appearance and potential for scarring.
Acute Cutaneous Lupus Erythematosus (ACLE) is often associated with a flare-up of systemic disease and is characterized by a distinctive malar rash. This rash, sometimes called the “butterfly rash,” is a flat or slightly raised redness that spreads across the cheeks and the bridge of the nose, typically sparing the creases next to the nostrils. ACLE lesions are highly sensitive to sun exposure and usually resolve without leaving a scar.
Another common pattern is Subacute Cutaneous Lupus Erythematosus (SCLE), which presents as non-scarring, reddish, scaly patches on sun-exposed areas of the body. These lesions frequently take on an annular, or ring-shaped, configuration or may resemble psoriasis. SCLE tends to appear on the arms, shoulders, and upper torso, generally avoiding the face and knuckles.
Chronic Cutaneous Lupus is primarily represented by Discoid Lupus Erythematosus (DLE), a more aggressive type of skin lesion. DLE lesions appear as thick, scaly, disk-shaped patches that often cause a change in skin color and can plug hair follicles. Unlike the acute and subacute forms, discoid lesions frequently lead to permanent scarring and hair loss in the affected area. None of these frequent cutaneous lupus forms produce true, tense, fluid-filled blisters (bullae).
When Lupus Causes Blisters
While the common lupus rashes are non-blistering, a rare and severe manifestation called Bullous Systemic Lupus Erythematosus (BSLE) directly causes blisters. BSLE is an acquired subepidermal blistering disease that occurs in a very small percentage of individuals who have systemic lupus. The underlying cause is a highly specific autoimmune attack where the body produces autoantibodies that target Type VII collagen. This protein is a major component of the anchoring fibrils, which secure the outer layer of the skin (epidermis) to the layer beneath it (dermis).
When autoantibodies attack Type VII collagen, the connection between the two skin layers weakens, leading to a separation that fills with fluid and forms a blister. The resulting blisters are typically large, tense sacs that can resemble those seen in other autoimmune blistering diseases. These eruptions can appear on normal or reddened skin, and they are commonly found on the trunk, face, and extremities. Ruptured bullae leave behind erosions and crusts that often heal with changes in pigmentation.
BSLE usually develops in people who have an established diagnosis of SLE, often during a period of active systemic disease affecting major organs like the kidneys. However, the blistering eruption can occasionally be the first sign of lupus. While the severity of the blistering does not always align with the activity of the systemic disease, parallel flares are frequently observed.
Distinguishing Lupus Blisters from Other Skin Conditions
The appearance of blisters in a person with lupus presents a diagnostic challenge because not all blistering lesions are caused by BSLE. Clinicians must rule out other common causes of blistering eruptions, which are often more likely than the rare BSLE. Drug-induced bullous reactions are a significant concern, as people with lupus take numerous medications that can trigger skin sensitivity and blistering. Infections, such as a severe herpes zoster outbreak, must also be considered as fluid-filled lesions.
Dermatologists use specific diagnostic tools to determine the precise cause of the blistering. A skin biopsy is performed to analyze a tissue sample under a microscope for characteristic features of a subepidermal blister with a high concentration of neutrophils. Direct Immunofluorescence (DIF) testing is also performed on the tissue to look for deposits of immune proteins, specifically IgG, at the dermal-epidermal junction.
The most definitive step in confirming BSLE is identifying the presence of autoantibodies against Type VII collagen. This process helps differentiate BSLE from other autoimmune bullous conditions, such as bullous pemphigoid, which target different proteins. An accurate diagnosis is necessary because the treatment for BSLE, which often involves high-dose immunosuppression, differs significantly from managing a drug reaction, which requires stopping the causative medication.