Dermatology MCQ - Inflammatory Dermatoses - Bullous systemic lupus erythematosus

A 28-year-old woman with a known history of systemic lupus erythematosus presents with a widespread, vesiculobullous eruption. The lesions are tense and are located on both sun-exposed and non-sun-exposed skin, including the trunk. Direct immunofluorescence of perilesional skin is performed. Which of the following immunofluorescence patterns is most characteristic of Bullous Systemic Lupus Erythematosus (BSLE)?

A. Linear deposition of IgG and C3 along the dermo-epidermal junction
B. Granular deposition of IgG and C3 along the dermo-epidermal junction
C. Intercellular deposition of IgG throughout the epidermis (fishnet pattern)
D. Granular deposition of IgA in the dermal papillae
E. Linear deposition of IgA along the dermo-epidermal junction

Correct Answer: A. Linear deposition of IgG and C3 along the dermo-epidermal junction

Explanation

Bullous Systemic Lupus Erythematosus (BSLE) is an autoimmune blistering disease that occurs in patients with established SLE. The blistering is due to an autoimmune response against type VII collagen, the primary component of anchoring fibrils, which is identical to the target antigen in epidermolysis bullosa acquisita (EBA).

• Direct Immunofluorescence (DIF) Findings: The hallmark of BSLE on DIF is a continuous, linear band of IgG and/or C3 deposited along the dermo-epidermal junction. This "lupus band" in BSLE is linear, which helps distinguish it from the more common non-bullous cutaneous lupus. While a positive lupus band test (granular deposition) can be seen in both lesional and non-lesional sun-exposed skin in SLE patients, the linear pattern is highly specific for the bullous variant.

Why other options are incorrect

• B. Granular deposition of IgG and C3 along the dermo-epidermal junction: This is the classic "lupus band" seen in non-bullous cutaneous lupus erythematosus (e.g., discoid lupus, subacute cutaneous lupus). It is not the characteristic finding for the vesiculobullous eruption of BSLE.

• C. Intercellular deposition of IgG throughout the epidermis (fishnet pattern): This is the pathognomonic DIF finding for pemphigus vulgaris and foliaceus, which are clinically distinct from BSLE.

• D. Granular deposition of IgA in the dermal papillae: This is the characteristic DIF finding in dermatitis herpetiformis, which is associated with celiac disease.

• E. Linear deposition of IgA along the dermo-epidermal junction: This is the hallmark of Linear IgA Disease, a separate autoimmune blistering condition.

Key Associations for Bullous Systemic Lupus Erythematosus (BSLE)

• Pathogenesis & Histopathology: Autoantibodies (predominantly IgG) target type VII collagen in the sub-lamina densa region. Histology typically shows a neutrophilic-rich inflammatory infiltrate with microabscesses in the dermal papillae and a subepidermal blister, resembling dermatitis herpetiformis or Linear IgA Disease. Direct immunofluorescence is diagnostic.

• Diagnostic Criteria: Requires a diagnosis of SLE, a vesiculobullous eruption, histology compatible with a subepidermal blistering disease, and a DIF showing linear or granular IgG, IgA, or IgM at the basement membrane zone. Negative serology for other bullous diseases (e.g., BP180, BP230) and confirmation of anti-type VII collagen antibodies (via salt-split skin indirect immunofluorescence or ELISA) support the diagnosis.

• Differential Diagnosis: The main differentials include other subepidermal blistering diseases such as Epidermolysis Bullosa Acquisita (EBA) (shares the same target antigen), Bullous Pemphigoid, Dermatitis Herpetiformis, and Linear IgA Disease.

• Management & Prognosis: BSLE often indicates active systemic disease. Management involves controlling the underlying SLE with systemic immunosuppressants. Dapsone is frequently used as a first-line treatment for the blistering itself due to its rapid effect on neutrophilic inflammation. Other agents include colchicine, corticosteroids, and more potent immunosuppressants like mycophenolate mofetil or rituximab. The prognosis is generally that of the underlying SLE.