Disseminated histoplasmosis mimicking post-vaccination side effects in an immunocompromised person with multiple sclerosis.

We describe the case of a gentleman with relapsing-remitting multiple sclerosis and chronic lymphocytopenia secondary to treatment with fingolimod who presented with disseminated histoplasmosis after receiving the third dose of the Moderna coronavirus disease 2019 (mRNA-1273) vaccine. Following the vaccination the patient noted fatigue which worsened over time along with gradual weight loss. A few months later he noted low-grade fever and finally shortness of breath. A diagnosis of disseminated histoplasmosis was performed based on urine, blood, and imaging data. He responded well to prolonged antifungal treatment. Fingolimod was discontinued and replaced with glatiramer acetate. He has been clinically stable until the time of this report, 33 months following symptom onset.