BG09 Acquired haemophilia A in mucous membrane pemphigoid: beware of spontaneous bleeding in immunobullous diseases

Abstract Acquired haemophilia A (AHA) is a rare autoimmune disorder characterized by the development of autoantibodies against clotting factor VIII, resulting in abnormal bleeding. It can be triggered by other immunological disorders, such as mucous membrane pemphigoid (MMP), a chronic autoimmune blistering disease that is characterized by mucocutaneous blistering and scarring. The coexistence of AHA and MMP is exceptionally rare and presents unique management challenges, especially in the older or frail patients. A 79-year-old woman presented in September 2023 with a 7-month history of large bullae on both feet and the upper limbs, trunk and oral mucosa. Treatment with doxycycline provided partial improvement. On review 1 year later she had ongoing erosions on the back and severe oral ulcerations causing difficulty eating and significant weight loss. Examination revealed erosions with milia on the upper back, tense bullae on the right hand, and buccal mucosal erosions. MMP was suspected, and treatment was initiated with prednisolone (10 mg once daily), doxycycline (200 mg once daily) and dapsone (50 mg once daily). Direct immunofluorescence (IMF) demonstrated IgG and C3 deposition at the basement membrane zone. Indirect IMF was positive at a titre of 1 : 800 with IgG deposition localized to the roof of salt-split skin. Anti-BP180 and anti-BP-230 antibodies were not detected by enzyme-linked immunosorbent assay, but anti-collagen VII antibodies were raised at 28 U mL−1. This was incongruous with a roof binding pattern on salt-split skin, and is suggestive of circulating antibodies to other basement membrane zone epitopes. Computed tomography imaging showed bilateral pleural effusions and a 6-mm nodule in the right middle lobe, further investigation of which is ongoing. Despite treatment, the patient experienced a flare-up characterized by extensive eroded lesions and numerous tense bullae, some haemorrhagic. Prednisolone was increased to 20 mg once daily and dapsone was replaced with mycophenolate mofetil (MMF) 1 g twice daily, but there was no significant improvement. In November 2024, the patient presented with extensive ecchymosis and cutaneous bleeding. Elevated activated partial thromboplastin time (51 s), reduced factor VIII levels and elevated factor VIII inhibitors confirmed AHA. Prednisolone was increased to 50 mg once daily, MMF was continued and tranexamic acid was added to support clotting. The bleeding episodes resolved and skin lesions were controlled on prednisolone 50 mg. The association of MMP and AHA has only rarely been reported before and is intriguing as both are prototypic antibody-driven diseases characterized by loss of B-cell tolerance. A number of dermatological conditions have been associated with AHA, including immunobullous and autoimmune diseases. Screening for AHA should be undertaken in dermatology patients with autoimmune diagnoses who develop spontaneous or unusual bleeding.