A significant fever in patients with cancer is always a serious concern. Though it usually indicates the presence of an infection, a source is sometimes difficult to detect – and is not always found – even after an extensive investigation. This often leaves the caring physician perplexed and concerned. As cancer patients undergo several types of treatments such as antineoplastic chemotherapy, immunotherapy, targeted therapy, radiation therapy, surgery, and blood transfusions, the differential diagnosis for fever can become more complicated and requires a carefully measured evaluation. Among the variety of causes of fever, one of not uncommon etiology is fever of paraneoplastic manifestation, which is a febrile condition occurring as a result of the biologic effects from cancer itself.

Precision Medicine is an emerging approach for disease treatment and prevention that takes into account individual variability in genes, environment, and lifestyle. Autoimmune diseases are those in which the body's natural defense system loses discriminating power between its own cells and foreign cells, causing the body to mistakenly attack healthy tissues. These conditions are very heterogeneous in their presentation and therefore difficult to diagnose and treat. Achieving precision medicine in autoimmune diseases has been challenging due to the complex etiologies of these conditions, involving an interplay between genetic, epigenetic, and environmental factors. However, recent technological and computational advances in molecular profiling have helped identify patient subtypes and molecular pathways which can be used to improve diagnostics and therapeutics. This review discusses the current understanding of the disease mechanisms, heterogeneity, and pathogenic autoantigens in autoimmune diseases gained from genomic and transcriptomic studies and highlights how these findings can be applied to better understand disease heterogeneity in the context of disease diagnostics and therapeutics.