Why Does Heartburn Occur?
To understand heartburn, let us look at the body's anatomy. The esophagus carries food and liquid to the stomach. A sphincter, or muscular valve, is located at the end of the esophagus at the border between the esophagus and stomach. Known as the lower esophageal sphincter (LES) this muscle contracts much the same as the anus does. The sphincter should maintain a certain pressure to keep the end of the esophagus closed so that stomach juices are not admitted. The LES muscle should only open when food is passed into the stomach.
Two major immune system genes under investigation are interleukin-12 subunit beta ( IL12B ) on chromosome 5q , which expresses interleukin-12B; and IL23R on chromosome 1p, which expresses the interleukin-23 receptor, and is involved in T cell differentiation. Interleukin-23 receptor and IL12B have both been strongly linked with psoriasis.  T cells are involved in the inflammatory process that leads to psoriasis.  These genes are on the pathway that upregulate tumor necrosis factor-α and nuclear factor κB , two genes involved in inflammation.  Recently, the first gene directly linked to psoriasis has been identified. A rare mutation in the gene encoding for the CARD14 protein plus an environmental trigger was enough to cause plaque psoriasis (the most common form of psoriasis).