Case description: We report a 75-year-old female with a severe reactivation of DLE after intravenous (IV) eculizumab for treatment of AQP4+ NMO. Her past medical history was remarkable for DLE, in remission for 30 years. She was diagnosed with NMO in late 2019 and started on Rituximab; in mid-2020, she had two exacerbations. At that point she was switched to Eculizumab (900 mg every week). After the third dose, a mild pruritic rash appeared in all extremities; this worsened after the fourth dose and became severe over the next 2 weeks, despite oral diphenhydramine, topical steroid application and discontinuation of eculizumab. Examination revealed well-defined, large (2-3 cm), scattered, pink, inflamed, disciform, ovoid, annular, and polycyclic plaques with trailing scale in arms, legs, and upper back. Dermatology determined this to be a case of DLE. She treated with 50 mg of prednisone 4 times a day for 4 days. Clinical improvement was observed over the following weeks.

The pathophysiology of drug-induced lupus erythematous (DILE) is poorly understood. It is suspected that abnormal expression of inflammatory cells and autoantibodies to multiple autoantigens are necessary for its development., This leads to the deposition of immune complexes in the tissues with stimulatory effects on B cells.^4-6 There exists preliminary evidence documenting autoimmune reactions with the use of IgG2/IgG4 monoclonal antibody.⁷

Rarely autoimmune reactions can be seen with use of eculizumab. Reactivation of DLE could be a possible side effect. Further research is needed to understand the immunogenicity of eculizumab.