Abstract
Eculizumab is a biologic medication used for the treatment of complement-related disorders including anti-acetylcholine receptor antibody-positive generalized myasthenia gravis. It targets C5 complement, preventing its cleavage into active terminal components. Thus, vaccination against encapsulated organisms is advised before starting this treatment. C5 also has a critical role against Cryptococcus neoformans infection. Here, we present a case of a 34-year-old man with a history of myasthenia gravis who was treated with prednisone and azathioprine in addition to eculizumab that was added to his regimen about a year ago, and who came to the hospital with headache, and was found to have Cryptococcus meningitis with disseminated cryptococcosis. The patient was negative for human immunodeficiency virus. He was treated with antifungal medications, and his condition improved. Although rarely reported, it is important to have a low threshold for diagnosis of cryptococcosis in patients on eculizumab given its complement inhibition mechanism of action.