Systemic onset juvenile arthritis (SoJIA) is another disease with systemic involvement that greatly benefi ted from the study of blood transcriptional profi les with the development of both therapeutic and diagnostic modalities [14, 16, 36, 37] . Diseases with specifi c organ involvement have also been the subject of signifi cant, yet not always extensive, blood profi ling eff orts. Blood signatures have, for instance, been obtained from patients with Following extraction, RNA is used as a template and amplifi ed in a labeling reaction. The labeled material captured by the microarray is imaged and relative abundance determined based on the strength of the signal produced by the fl uorochromes that serve as reporters in this assay. The Nanostring technology measures RNA abundance at the single molecule level. RNA serves as starting material for this assay, which does not involve the use of enzymes for amplifi cation or labeling. Capture and reporter probes form complexes in solution with RNA molecules. These complexes are captured on a solid surface and imaged. Molecule counts are generated based on the number of reporter probes detected on the image. The reporter consists of a string of seven fl uorochromes, with four diff erent colors available to fi ll each position. Up to 500 diff erent transcripts can be detected in a single reaction on this platform. For RNA sequencing (RNA-seq) the starting RNA population must fi rst be converted into a library of cDNA fragments. High throughput sequencing of such fragments yields short sequences or reads that are typically 30 to 400 bp in length. For a given sample tens of millions of such sequences will then be uniquely mapped against a reference genome. The density of coverage for a given gene determines its relative level of expression. Similarities and diff erences between these technology platforms should be noted. For instance, microarrays and Nanostring technologies rely on oligonucleotide probes to capture complementary target sequences. Nanostring and RNA-seq technologies measure abundance at the single molecule level, with results expressed as molecule counts and sequence coverage, respectively. Microarray and RNA-seq technologies require extensive sample processing, which include amplifi cation steps. dsDNA, double-stranded DNA. Nanostring RNA-seq multiple sclerosis [38, 39] . Given the inaccessibility of the brain, blood constitutes a particularly attractive source of surrogate molecular markers for this disease. Th ese eff orts have yielded a systemic signature and identifi ed potential predictive markers of clinical relapse and response to treatment [40] [41] [42] . Transcriptional signatures have also been generated in the context of dermatologic diseases. In this case, the target organ being readily accessible, eff orts have been focusing on profi ling transcript abundance in skin tissues [43, 44] . However, systemic involvement has been recognized in recent years to be an important component of autoimmune skin diseases and unique blood transcriptional profi les have also been identifi ed in patients with, for example, psoriasis [45] [46] [47] .