Which finding would support a diagnosis of drug-induced lupus?

Which finding would support a diagnosis of drug-induced lupus?

• A. Antihistone antibodies
• B. Antibodies to Smith antigen
• C. Presence of RF
• D. Antibodies to SS-A and SS-B antigens

Answer: (A)

Drug-induced lupus is an autoimmune reaction triggered by certain medications. The finding that most strongly supports this diagnosis is antihistone antibodies. These antibodies are commonly seen in drug-induced lupus and help distinguish it from idiopathic systemic lupus erythematosus, where anti-dsDNA and anti-Smith antibodies are more typical. Antibodies to Smith antigen are highly specific for SLE and point away from drug-induced lupus. Rheumatoid factor is nonspecific and can be seen in many conditions, not particularly indicative of drug-induced lupus. Antibodies to SS-A and SS-B are associated with Sjögren syndrome (and can appear in some SLE cases), but they do not specifically indicate drug-induced lupus.

Drug-induced lupus is an autoimmune reaction triggered by certain medications. The finding that most strongly supports this diagnosis is antihistone antibodies. These antibodies are commonly seen in drug-induced lupus and help distinguish it from idiopathic systemic lupus erythematosus, where anti-dsDNA and anti-Smith antibodies are more typical. Antibodies to Smith antigen are highly specific for SLE and point away from drug-induced lupus. Rheumatoid factor is nonspecific and can be seen in many conditions, not particularly indicative of drug-induced lupus. Antibodies to SS-A and SS-B are associated with Sjögren syndrome (and can appear in some SLE cases), but they do not specifically indicate drug-induced lupus.