Frequency of latent tuberculosis in patients with multiple sclerosis screened for the prescription of alemtuzumab

Introduction: Tuberculosis is a leading infectious cause of death in the world and patients receiving immunosuppressants are at an increased risk of the disease. Alemtuzumab was associated with high incidence of tuberculosis in Asian patients with hematologic malignancies and autoimmune cytopenias, but little is known about the need to screen for latent tuberculosis in patients with multiple sclerosis before alemtuzumab in South America. Objective: To define the frequency of latent tuberculosis in patients with multiple sclerosis screened for the prescription of alemtuzumab in a country endemic for tuberculosis. Methods: We reviewed medical records of 24 patients with multiple sclerosis as routine before the prescription of alemtuzumab in our service in São Paulo, Brazil, from 2022 to 2023. We collected age, sex, disease duration and median EDSS to characterize our sample. Our main outcome was the frequency of latent tuberculosis, defined as positive PPD tests defined by more than 5 mm in the absence of clinical or radiological signs of active tuberculosis. Results: Out of 24 patients, 4 (16,6%) presented with latent tuberculosis. Our sample was predominantly male (3:1), with a median age of 33 years old, median disease duration of 7,25 years and median EDSS of 3,5. Conclusion: One in six patients with multiple sclerosis presented latent tuberculosis in our sample, reinforcing the need of screening and, if deemed necessary, treating for latent tuberculosis when planning to start alemtuzumab.