Abstract Brazil has the second largest number of leprosy cases in the world; nevertheless, late diagnosis is common. We report the case of a male patient with pain and numbness in both hands and feet for six years with positive rheumatoid factor and anticardiolipin under rheumatoid arthritis treatment for five years. Examination revealed diffuse cutaneous infiltration and leonine facies, characteristic features of lepromatous leprosy. Autoantibodies such as rheumatoid factor and anticardiolipin are markers of rheumatic autoimmune diseases, but their presence is also described in leprosy. We report the present case in order to alert health professionals to remember leprosy, even in areas where the disease is considered eliminated as a public health problem, avoiding misinterpretations of serologic findings and misdiagnosis.