Bullous Pemphigoid in Patients with Amyotrophic Lateral Sclerosis: A Retrospective Study of 1,067 Cases.

Background　Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that affects motor neurons. Bullous pemphigoid (BP) is an autoimmune blistering disease associated with autoantibodies against BP180 and BP230. Previous studies have suggested an increased incidence of BP in patients with ALS. However, the neurological status and disease severity of patients with ALS at the time of BP onset remain insufficiently characterized. This study aimed to investigate the frequency and clinical characteristics of BP in patients with ALS.Methods　In this retrospective study, we reviewed the medical records of 1,067 patients with ALS who were admitted to our institution between April 2010 and May 2025. Patients who developed BP after the onset of ALS were identified. BP was diagnosed by dermatologists based on clinical findings and, when available, by immunological or histopathological examinations. Disease severity at BP onset was assessed based on the ambulatory status and ventilatory support requirements.Results　Seven of the 1,067 patients (0.66%) developed BP after ALS onset. The median interval between ALS and BP onset was 8.0 years (IQR 5.0-16.5). At BP onset, four patients (57.1%) were bedridden, four (57.1%) required tracheostomy and invasive ventilation, and two (28.6%) required non-invasive ventilation. Five patients (71.4%) required enteral feeding. The median age at BP onset was 68.0 years (IQR, 64.0-72.5). BP180 antibody testing was positive in three of the six patients. The lesions most commonly involved both the extremities and the trunk.Conclusion　BP may occur more frequently in ALS patients than in the general population. Clinicians should consider BP when evaluating cutaneous lesions in patients with ALS.