Bullous Pemphigoid is an uncommon autoimmune skin disorder characterized by subepidermal blistering. Pathophysiology involves autoantibodies targeted against basal hemidesmosome proteins which trigger an inflammatory cascade and the formation of pruritic urticarial plaques that evolve into bullae. Literature review showed that this autoimmune blistering disease can be seen in neurologic disorders such as Alzheimer’s, Parkinson’s, and multiple sclerosis. We present an exceptionally rare case of bullous pemphigoid and autoimmune encephalitis, treated successfully with methylprednisolone and IVIg.

A 92-year-old previously independent woman presented with confusion associated with visual, auditory, and tactile hallucinations. Her symptoms started shortly after the appearance of a new rash involving her face, arms, and trunk. Neurologic examination revealed pseudobulbar affect with difficulty following commands and a MOCA score of 5/30. Work-up with MRI Brain and EEG was unrevealing. Lumbar puncture demonstrated mild pleocytosis (47/cmm WBC), elevated protein (70 mg/dL) with negative culture, cytology, meningitis/encephalitis, and autoimmune encephalopathy/paraneoplastic panels. Skin punch biopsy results were consistent with bullous pemphigoid. There was clinical suspicion for autoimmune encephalitis in the setting of her autoimmune skin disorder. She was started on empiric high dose methylprednisolone followed by a 2g/kg course of IVIg over 5 days, with robust clinical improvement. Her hallucinations and encephalopathy resolved, and she was discharged at her baseline.

The relationship between autoimmune blistering skin disorders and systemic inflammatory/autoimmune diseases have been described in literature as an “autoimmune diathesis”. This is where similar antibodies and shared epitopes lead to cross-reactivity and inflammation in both systems. This phenomenon has been described when inflammatory conditions combine with neurodegenerative conditions such as Alzheimer's and Parkinson's. However, there remains limited literature regarding the dual development of autoantibody-mediated skin disorders and acute autoimmune encephalitis. Our case highlights the importance of maintaining a high index of suspicion for autoimmune skin disorders triggering CNS autoimmune disease.