Blood gene expression profiling has led to major advances in the field of 
rheumatology over the last few decades. Specifically, DNA microarray technology 
has been integral in increasing our knowledge of key players in the pathogenesis 
of some rare pediatric rheumatic diseases. Our group, using microarray analysis, 
identified the interferon (IFN) gene signature in pediatric systemic lupus 
erythematosus (SLE) and has published data that suggest high doses of 
intravenous corticosteroid treatment may have benefit over strictly oral 
regimens. Additionally, DNA microarray technology led to our discovery that the 
interleukin (IL)-1 gene signature is associated with systemic juvenile 
idiopathic arthritis (sJIA) and to the use of IL-1 blockade with anakinra in 
this disease. We also reported the biologic rationale for use of anakinra early 
in the disease course. Anakinra is now being used as first-line treatment in 
sJIA in multiple centers. Herein, we review how information obtained from blood 
gene expression profiling has changed our clinical practice.