Comment
Diagnosis of BSLE
Bullous systemic lupus erythematosus is a rare cutaneous complication of SLE. It typically affects young black women in the second to fourth decades of life.1 It is a heterogeneous disorder with several clinical variants reported in the literature, and it can be mistaken for bullous pemphigoid, epidermolysis bullosa acquisita (EBA), linear IgA bullous dermatosis, and DH.1-3 Despite its varying clinical phenotypes, BSLE is associated with autoantibodies to the EBA antigen, type VII collagen.1
Current diagnostic criteria for BSLE, revised in 1995,5 include the following: (1) a diagnosis of SLE, based on criteria outlined by the American College of Rheumatology6; (2) vesicles or bullae, or both, involving but not limited to sun-exposed skin; (3) histopathologic features similar to DH; (4) DIF with IgG or IgM, or both, and IgA at the basement membrane zone; and (5) indirect immunofluorescence testing for circulating autoantibodies against the basement membrane zone, using the salt-split skin technique.
Clinical Presentation of BSLE
The classic phenotype associated with BSLE is similar to our patient’s original eruption, with tense bullae favoring the upper trunk and healing without scarring. The extensor surfaces typically are spared. Another presentation of BSLE is an EBA-like phenotype, with bullae on acral and extensor surfaces that heal with scarring. The EBA-like phenotype usually is more difficult to control. Lesions appearing clinically similar to DH have been reported, either as DH associated with SLE (later postulated to have been BSLE) or as herpetiform BSLE.1,4,7-10
Histopathology of BSLE
The typical histologic appearance of BSLE is similar to DH or linear IgA bullous dermatosis, with a predominantly neutrophilic inflammatory infiltrate in the upper dermis and a subepidermal split. Direct immunofluorescence shows broad deposition of IgG along the basement membrane zone (93% of cases; 60% of which are linear and 40% are granular), with approximately 70% of cases showing positive IgA or IgM, or both, at the basement membrane zone. Indirect immunofluorescence performed on 1 M NaCl salt-split skin showed staining on the dermal side of the split, similar to EBA.11
Treatment Options
Rapid clinical response has been reported with dapsone, usually in combination with other immunosuppresants.1,2 A subset of patients does not respond to dapsone, however, as was the case in our patient who tried dapsone early in the disease course but was not effective. Other therapies including azathioprine, cyclophosphamide, mycophenolate mofetil, and antimalarials have been used with some success.3
Rituximab, an anti-CD20 monoclonal antibody, has been used off label to treat BSLE cases that are resistant to dapsone, corticosteroids, and other immunosuppressants.12 Rituximab functions by depleting CD20+ B cells, thus altering the production of autoantibodies and, in the case of BSLE, reducing the concentration of circulating anti–type VII collagen antibodies. Rituximab was approved by the US Food and Drug Administration in 1997 for the treatment of non–Hodgkin lymphoma and later for chronic lymphocytic leukemia, rheumatoid arthritis, granulomatosis with polyangiitis (Wegener granulomatosis), and microscopic polyangiitis.12 Off-label administration of rituximab to treat autoimmune bullous dermatoses has been increasing, and the drug is now approved by the US Food and Drug Administration to treat pemphigus vulgaris (as of June 2018).13
In 2011, Alsanafi et al12 reported successful treatment of BSLE with rituximab in a 61-year-old black woman who had rapid clearance of skin lesions. Our patient had rapid resolution of cutaneous disease with rituximab after the second infusion in a 2-infusion regimen. Interestingly, rituximab is the only agent that has reliably resulted in resolution of our patient’s cutaneous and systemic disease during multiple episodes.
There is little information in the literature regarding the duration of response to rituximab in BSLE or its use in subsequent flares. Our patient relapsed at 2 years and again 3 years later (5 years after the initial presentation). The original cutaneous outbreak and subsequent relapse had classic clinical and histological findings for BSLE; however, the third cutaneous relapse was more similar to DH, given its distribution and appearance. However, the histopathologic findings were the same at the third relapse as they were at the initial presentation and not reflective of DH. We propose that our patient’s prior treatment with rituximab and ongoing immunosuppression at presentation contributed to the more atypical cutaneous findings observed late in the disease course.
Conclusion
We report this case to highlight the heterogeneity of BSLE, even in a single patient, and to report the time course of treatment with rituximab. Although BSLE is considered a rare cutaneous complication of SLE, it is important to note that BSLE also can present as the initial manifestation of SLE.7 As such, BSLE should always be included in the differential diagnosis for a patient presenting with a bullous eruption and symptoms that suggest SLE.
This case also illustrates the repeated use of rituximab for the treatment of BSLE over a 5-year period and justifies the need for larger population-based studies to demonstrate the efficacy of rituximab in BSLE.