Anti-histone antibody is an important immunological marker for the diagnosis of drug induced lupus (DIL). Although anti-histone antibodies are detected in approximately 30% to 60% of patients with systemic lupus erythematosus (SLE), their presence is much higher in DIL patients. They are detected in about 95% of DIL patients, which is more important diagnostically. DIL is clinically similar to SLE, except that the former patients do not have kidney or central nervous system involvement. In addition, DIL patients do not demonstrate the multiple types of antinuclear antibodies (ANAs) often found in SLE patients.