Primary biliary cirrhosis describes a chronic disease characterized by inflammation of the bile ducts in the liver. The bile ducts carry bile, a yellowish-brown substance produced by the liver, to the gallbladder and then to the small intestine to aid in the breakdown of fats. Inflammation of the bile ducts inhibits the flow of bile causing bile to build up in the liver, which can damage liver tissue. Although the exact cause of primary biliary cirrhosis remains unknown, several factors contribute to the disease.
Genetic Factors
Doctors classify primary biliary cirrhosis as an autoimmune disease. In autoimmune diseases, the immune system attacks the body's own tissues. As with many autoimmune diseases, primary biliary cirrhosis can occur due to genetic factors.
The genetic component of primary biliary cirrhosis is complex, meaning that there is likely not one gene mutation associated with the disease. Instead, changes to several different genes, either alone or in combination, lead to a susceptibility for developing the disease.
It can be difficult to distinguish between the effects of a shared environment and genetic factors. One of the best means for determining the effects of genetics is the comparison of the disease in identical twins, which share the same genetic material, and fraternal twins, which share genetic material the same as any sibling relationship. Information published in 2008 in "Clinical Liver Disease" reveals that 63 percent of identical twin pairs in a study both developed the disease, revealing a strong genetic factor.
Environmental Factors
Although patients with primary biliary cirrhosis possess a genetic susceptibility for the disease, researchers believe that genetics combined with an environmental trigger, such as an infection, may be the actual cause of the abnormal immune response, explains MayoClinic.com. Many women report suffering from urinary tract infections often caused by the intestinal bacteria E. coli prior to the onset of primary biliary cirrhosis. Exposure to certain chemicals may also trigger the onset of primary biliary cirrhosis. Additionally, excessive alcohol consumption may contribute to the disease because alcohol can damage the liver, leaving it susceptible to inflammation.
Primary biliary cirrhosis most commonly occurs between the ages of 40 and 60 and affects more women than men, according to the National Digestive Diseases Information Clearinghouse.
Autoimmune Response
The problems in primary biliary cirrhosis begin with inflammation in the smallest ducts of the liver. T cells invade and destroy the liver cells within these bile ducts, causing inflammation and triggering the production of proteins that attract more T cells, according to MayoClinic.com. This ongoing cycle of immune response leads to damaged liver cells and the buildup of scar tissue. As scar tissue builds up, liver function decreases, leading to complications such as vitamin deficiencies, cognitive impairments, enlarged spleen, bleeding and bruising.
