Figure 2. Refining the Relationship between Genotype and Phenotype in Complex Inflammatory Diseases.
(a) Traditionally a disease is considered as a single phenotype, with genes or loci conferring risk to two diseases shown as overlapping in a Venn diagram. (b) We propose a new view of the genotype-phenotype relationship in which different sets of loci are responsible for mechanistically distinct subtypes of diseases, and the sum of these subtypes constitutes the overall diagnosis. Here two disease subtypes are indicated for simplicity, but many such sub-types may exist, and sets of overlapping risk loci may be associated with these multiple mechanistically distinct disease phenotypes.