Drug-Induced Lupus Associated with Clozapine

Clinical Presentation and Serological Findings

The European Society of Cardiology guidelines recommend monitoring for signs of drug-induced lupus-like syndrome, including arthralgia, muscle aches, joint pain or swelling, pericarditis, pleuritis, rash, or fever, and suggest ANA testing and drug discontinuation if suspected 2
A speckled pattern on antinuclear antibody (ANA) testing can occur in drug-induced lupus (DIL), although homogeneous patterns are more typical 1
The homogeneous staining pattern is typically associated with systemic lupus erythematosus (SLE) and DIL, reacting with histones and DNA 1
When interpreting ANA results, both the pattern and titer should be reported, with a screening dilution of 1:160 on conventional HEp-2 substrates often suitable for adult populations being evaluated for systemic autoimmune rheumatic diseases 4

ANA testing is an important tool in the diagnosis of DIL, and the pattern and highest dilution should be reported 4
In cases of suspected DIL with negative ANA, testing for histone antibodies may be valuable as they are present in most active DIL cases 4