Linear IgA bullous dermatosis associated with immunotherapy.

Linear IgA bullous dermatosis (LABD) is a rare mucocutaneus blistering autoimmune disease caused by IgA autoantibodies. Its clinical manifestation can be indistinguishable from bullous pemphigoid (BP), a similar autoimmune bullous disease caused by IgG and IgE autoantibodies. Although BP has been reported as an adverse cutaneous effect of immunotherapy, LABD has rarely been associated with immunotherapy in the literature. We present the case of a 67-year-old woman with metastatic ovarian cancer receiving anti-PD1 and anti-CTLA4 with new onset pruritic tense bullae to the trunk, hands, elbows (in annular distribution) that occurred after immunotherapy. Skin biopsy showed subepidermal blister with abundant neutrophils on H&E histology, and linear IgA staining at the basement membrane on direct immunofluorescence consistent with the diagnosis of LABD. The condition did not improve on initial prednisone taper, but blisters rapidly resolved a few days after initiation of dapsone therapy. We favor that our patient's LABD is secondary to her immunotherapy. Our case highlights the importance of both H&E histology and direct immunofluorescence in diagnosis of blistering disorders in patients on immunotherapy to help in choosing the most effective treatment option in an attempt to avoid discontinuation of immunotherapy.