Primary biliary cirrhosis: a genetic liver disorder

Primary biliary cirrhosis, also known as primary biliary cholangitis, is a disease characterized by progressive destruction of liver cells, which can lead to a number of serious complications. It is known that there may be genetic susceptibility in the development of this disease, although environmental factors also play a key role in its development.

Before knowing how genes play a role in the risk of primary biliary cirrhosis, it’s important to understand what this disease is, what its main symptoms are and what we can do to prevent it.

 

What is primary biliary cirrhosis?

Primary biliary cirrhosis is a rare autoimmune disease that causes a progressive destruction of the intrahepatic bile ducts, which prevents the outflow of bile. As a consequence, fibrosis of the bile ducts develops and can lead to cirrhosis [3].

In a normal situation, the bile ducts transport the bile produced in the liver to the gallbladder. From there, it continues its journey to the small intestine in order to assist in the digestive process, helping to eliminate cholesterol and toxins from the body [1].

When these ducts are destroyed, bile begins to accumulate, causing liver damage and scarring. This causes a multitude of symptoms and major health problems, including death. Its annual incidence rate is between 0.7 and 49 cases per million inhabitants, while its prevalence ranges from 6.7 to 940 cases per million.  Incidence refers to the number of new cases of the disease that are diagnosed within a specific population during a given period of time, and allows us to measure the risk of developing a disease in the population in which it’s been calculated. Prevalence, on the other hand, refers to the total number of cases in a population, including both new and previously diagnosed cases, and provides an understanding of the burden of a disease in the population. 

Ninety percent of diagnosed cases of primary biliary cirrhosis in the world occur in women. Although it’s a disease that could develop at any age, it’s most prevalent between the ages of 50 and 70. 

Symptoms of primary biliary cirrhosis

In the early stages of the disease, most patients are asymptomatic. Many of them discover that they have this disorder through a routine blood test. Some people even remain symptom-free after diagnosis. In those cases where symptoms do occur, they usually include:

• Fatigue.
• Itching: usually starts on the soles of the feet and palms of the hands and is worse at night.
• Upper right abdominal pain.
• Pain in muscles, bones and joints.
• Dry mouth and eyes.
• Dark coloring of the skin.
• Weight loss for no apparent reason.

In more advanced stages, primary biliary cirrhosis can also produce jaundice, which consists of yellowing of the skin and the conjunctivae of the eyes.

What causes primary biliary cirrhosis?

Primary biliary cirrhosis is known to be caused by a combination of genetic and environmental factors. As an autoimmune disease, it is the body that generates an erroneous response by causing the body to attack its own cells.

Experts believe that this response occurs upon interaction with one or more external factors, increasing the risk of disease when there’s a genetic predisposition [6].  

If we want to prevent primary biliary cirrhosis, we can try to act on some of the actionable risk factors that seem to increase the probability of developing it, which are the following:

• Sex: women are more likely to have it than men.
• Age: most diagnoses occur between the ages of 50 and 70.
• Ethnicity: it is more common in people of Northern European descent.
• Smoking. 
• Some types of infections, such as urinary tract infections.
• Exposure to toxic substances.

 

How do genetics play a role in primary biliary cirrhosis?

 

Genetics can influence the development of primary biliary cirrhosis in several ways. Thanks to scientific research, genetic mutations have been identified in certain genes that are associated with an increased risk of developing this pathology.

A study carried out in people diagnosed with primary biliary cirrhosis has revealed that, in the case of monozygotic twins, the probability that if one of them is diagnosed with the disease, the other will also develop it is 63% [4].

On the other hand, there are also studies showing that siblings of people with primary biliary cirrhosis have 10.5 times the relative risk of developing the disease [4]. It is also known that variations in genes linked to pathways that promote inflammation may be directly involved in the development of this pathology [5]. 

In addition, primary biliary cirrhosis is commonly associated with other diseases of an autoimmune nature, such as Sjogren’s syndrome, scleroderma, Raynaud’s disease and CREST syndrome.

If you want to know what your genes say about your predisposition to primary biliary cirrhosis and a host of other diseases, you can find out with a genetic health test from 24Genetics. With a simple saliva sample, our experts will prepare a complete report for you to know your predisposition to develop, throughout your life, more than 200 pathologies. Click here to access a sample report and check all the information available to you.

 

Bibliography

[1] Primary biliary cirrhosis – University of Illinois Hospital & Health Sciences System [accessed Feb. 2023] Available at: https://hospital.uillinois.edu/es/primary-and-specialty-care/hepatologia-enfermedad-del-higado/%C3%A1reas-de-especialidad/cirrosis-biliar-primaria

[2] Primary biliary cirrhosis – Revista Española de Enfermedades Digestivas print version ISSN 1130-0108 vol.99 no.6 [published Jun. 2007; accessed Feb. 2023] Available from: https://scielo.isciii.es/scielo.php?script=sci_arttext&pid=S1130-01082007000600011

[3] Primary biliary cirrhosis – Redacción Médica [accessed Feb. 2023] Available at: https://www.redaccionmedica.com/recursos-salud/diccionario-enfermedades/cirrosis-biliar-primaria

[4] Primary biliary cirrhosis: new pathogenic mechanisms – J.F. Medina – Gastroenterol Hepatol. 2007;30(Suppl 1):14-8 – Gene Therapy and Hepatology Division. Center for Applied Medical Research (CIMA) and University Clinic. School of Medicine. University of Navarra. Pamplona. Pamplona. Spain. – XXXII National Congress of the Spanish Association for the Study of the Liver [published 2007; accessed Feb. 2023].

[5] Primary biliary cirrhosis (Mells, 2011) – Garrett Dunlap, B.S [published Jul. 2019; accessed Feb. 2023] Available from: https://nebula.org/blog/es/genetica-de-cirrosis-biliar-primaria-mells-2011/

[6] Primary biliary cholangitis – Mayo Clinic staff [published Sep. 2021; accessed Feb. 2023] Available at: https://www.mayoclinic.org/es-es/diseases-conditions/primary-biliary-cholangitis/symptoms-causes/syc-20376874