Multidrug therapy (WHO/MDT) in multibacillary leprosy consists of treatment with rifampicin, dapsone and clofazimine. However, adverse effects can cause the patient to abandon treatment. We report on a patient who presented agranulocytosis and hemolytic anemia associated with this treatment regime. We also examined the importance of laboratory exams for diagnosis and follow-up of the patient, and for early detection of adverse effects, with a view to improving adhesion to treatment and contributing to the eradication of Hansen's disease as a public health issue.