A Rash of Rashes: Multiple Sclerosis, Natalizumab Therapy, Bullous Pemphigoid

Background: To describe the appearance of bullous pemphigoid that occurred during Natalizumab infusions that could be mistaken for an allergic or infusion reaction.

Objectives: Natalizumab discontinuation can occur due to allergic reactions manifest as skin eruptions.

Methods: 51 year old female with relapsing remitting multiple sclerosis complained of skin itching and then developed a multiple skin urticaria shortly after the 73^rdnatalizumab infusion. This was initially considered to be an allergic reaction related to medication. Concurrent oral medications were discontinued but the skin eruptions persisted and evolved to blistering bullae. Despite discontinuation of Natalizumab the skin eruptions persisted and further evolved. Dermatological consultation with biopsy confirmed a diagnosis of bullous pemphigoid. Treatment with Cellcept and steroids were initiated.

Results:  Bullous pemphigoid is an uncommon autoimmune skin disorder seen in <0.001% of the population. Auto-antibodies directed against the cell surface of keratinocytes, producing acantholysis that leads to intraepithelial blisters in the skin and/or mucous membranes can be seen in condition. This disorder can occur independent of other disorders, and has also been related to medications, several autoimmune disorders and has been occasionally reported in patients with Multiple Sclerosis. Although the underlying cause of bullous pemphigoid is unknown, treatment can be helpful but this disorder can also result in increased morbidity and mortality.

Conclusions: Not all skin reactions that occur during or after Natalizumab infusion are allergic and related to therapy. Some skin reactions can be serious reactions necessitating therapy discontinuation due to the need to initiate other therapies. Vigilance as well as prompt and accurate identification of skin reactions, occurring during or thought to be related to infusion, is needed to determine the appropriate course of treatment. Differentiating serious skin reactions from non-serious or unrelated reactions are important so that appropriate treatment and/or modification of treatment plan and infusion care needs are addressed.