The Role of Family History in Psoriatic Disease

Genes hold the to key to explaining how the immune system becomes activated in psoriatic disease, an autoimmune condition that includes two specific inflammatory conditions: psoriasis and psoriatic arthritis (PsA). When researchers look for genes specific to psoriatic disease, they try to determine what a gene would do normally, and also, how it behaves in a person who has psoriasis or psoriatic arthritis. The process is a very tedious one for researchers because they believe more than one gene is associated with psoriatic disease development.

Psoriatic disease and all autoimmune diseases are conditions where the immune system attacks healthy cells in the body. Often times, these diseases run in families, and, chances are, you are not the only one in your family that has psoriatic disease. Additionally, family history may also explain disease severity. Here is what you need to know about the role family history plays in the development and progression of psoriatic disease.

Gene-Disease Process

Your genes tell every cell in your body how to act. In doing, they control everything from your height to your hair and eye color. People are different and unique because of gene variations, which are encoded in the sequences of DNA present on the chromosomes in the nucleus of each cell.

Genetic disorders can be caused by a mutation/variant in a single gene or mutations/variants in multiple genes. For some genetic diseases, inheriting the gene variants is not enough to get the disease; certain environmental triggers or factors are required.

Some disorders may be described as “running in the family” if more than one person in the family has the disease. Both common and rare diseases can run in families. Disorders that affect multiple family members are caused by gene mutations passed down from parent to child.

Family History

Your family medical history is a record of health information about you and your close relatives. A complete family history record includes information about three generations of relatives, including children, siblings, parents, aunts, uncles, grandparents, nephews, nieces, and cousins.

Because families have genes, environment, and lifestyle as common factors, these are clues about medical conditions that may run in families. Patterns related to medical disorders among relatives help medical professionals to determine whether you, your family members, and future generations may be at risk for a certain disease.

Family history is especially helpful in providing insight on risk for rare conditions caused by single-gene mutations, including cystic fibrosis and Huntington disease. Interestingly, despite the rareness of single-gene disorders, their inheritance patterns are very well understood, which isn’t the case for other genetic disorders, including psoriatic disease.

An inheritance pattern is the way in which a trait or disease is passed down through the generations. For example, some dominant traits, such as brown eye color, require transmission of a gene variant from only one parent. Recessive traits, on the other hand, require inheriting the gene variant from both parents for the trait to be seen.

Humans have 23 pairs of chromosomes, with 22 of them called autosomes. The 23d pair are the sex chromosomes (X and Y), with females inheriting an X from each parent (and they are XX) and males inheriting an X from the female parent and a Y from the male parent (they are XY).

When a recessive gene mutation is transmitted on the X chromosome, male offspring are more likely than female offspring to display the trait (e.g. color blindness and some forms of muscular dystrophy) because there is no second X chromosome to provide a normal copy of the gene. Female offspring would have an X from each parent, which might mask or modify the condition, depending on whether it is a dominant or recessive condition. As well, there are rare conditions that are only passed on the Y chromosome, so only males inherit them, through their father and paternal line only.

Genes and Psoriatic Disease

According to the National Psoriasis Foundation, up to 10% of the population inherits one or more genes that could increase their risk for developing psoriasis. While psoriatic arthritis has an unknown inheritance pattern, up to 40% of people who get the condition have at least one family who has PsA or psoriasis.

Having a family member with PsA or psoriasis does not mean you will actually develop one or both conditions. The reasons some people with genetic risk do not develop psoriatic disease are that either:

• They don’t have a specific or correct collection of gene features
• They have not had exposure to certain environmental triggers

This means having an increased risk due to genes and family history means a higher chance of developing the condition, but only if certain other characteristics exist. For this reason, it is impossible to predict whether a person will actually develop psoriatic disease.

Genetic Risk

Researchers are continually looking for specific genes and genetic causes related to psoriasis and PsA.

Psoriasis

Research on psoriasis has identified several inflammatory proteins—called cytokines—that are involved in the disease. This inflammatory response is due to gene mutations called alleles. Psoriasis research has led researchers to the belief one specific allele—called HLA-Cw6—might be linked to passing on of the diseases through families. In more recent years, researchers have discovered the presence of HLA-Cw6 alone isn’t enough to cause a person to develop the disease and more research is still needed to understand the relationship between HLA-Cw6 and psoriasis. Further study has led to the identification of around 25 other genes and gene variants associated with the development of psoriasis.

Researchers have been able to identify a rare gene mutation linked to psoriasis, as reported in 2012 in The American Journal of Human Genetics. The rare gene mutations—in a gene called CARD14—are associated with the development of plaque psoriasis, the most common type of psoriasis. It is believed that these mutations can cause plaque psoriasis in people exposed to environmental triggers, such as infections. A second report on the CARD14 mutation finds the mutation is present in large families with multiple family members with psoriatic disease.

Psoriatic Arthritis

Only recently have researchers been able to point to specific gene markers related to PsA. According to one study reported in 2015 in the journal Nature Communications, there are unique gene variants of the IL23R and on chromosome 1 that are specifically linked to the development of PsA.

In identifying these two markers, researchers performed genetic sequence testing on 1,962 people with psoriatic arthritis and 8,923 control subjects without psoriasis or PsA. According to the study’s authors, this discovery could help healthcare providers better identify people with psoriasis who are the most at risk for PsA, push for the development of drugs specifically for PsA, and offer insight as to why some current treatments are better at treating skin symptoms than with treating joint symptoms.

Findings

Genetic studies on psoriatic disease are helpful in giving healthcare providers and their patients an indication of risk for developing PsA, psoriasis, or both. Most of these newer findings are insightful, but they don’t offer answers as to why some people with genetic risk develop psoriatic disease and why others don’t. Further, even the way that genes specific to PsA or psoriasis are passed down from patient to child is still not fully understood.

Disease Effect

Family history may be helpful in determining the effect psoriatic disease has on a person. This effect may include disease severity, musculoskeletal features, and skin characteristics, according to results of a study published in Arthritis Care & Research. The goal of the study was to determine how family history affected disease characteristics in PsA or psoriasis. Of the total 1,393 study participants, 31.9% (444 patients) had a family history of psoriatic disease. These were mostly women, had an earlier disease onset, and had more severe disease, including less potential for remission (a period of little or no disease activity) or minimal disease activity and more deformity, enthesis (inflammation of sites where tendons or ligaments insert into the bone), and nail disease. 

Some of the findings of the researchers were:

• Family history of psoriasis was associated with earlier psoriasis onset and enthesitis. 
• Family history of PsA was associated with lower plaque psoriasis risk and higher deformity risk.
• Family of PsA with family history of psoriasis increased risk for deformity and decreased risk for plaque psoriasis risk.

A Word From Verywell

You can find out about your family medical history for psoriatic disease by talking to relatives who have the condition. Knowing your family history for psoriatic disease can help you to take the steps necessary to reduce your risk for developing psoriatic arthritis or psoriasis. Your family history may also be helpful to your healthcare provider in creating a treatment plan that increases the potential for minimal disease activity and reduces disease complications.

For people who have not been diagnosed, but have a family history of psoriatic disease, knowing family history can help you to take necessary steps to reduce your risk. Your healthcare provider will encourage you to come in for regular check-ups or testing to get ahead of any problems and to treat the disease early should you develop psoriatic disease. Early, aggressive treatment is the key to better outcomes, including remission and reduced risk for complications such as joint damage.

Additionally, it is important to adopt lifestyle changes, such as a healthy diet, getting regular exercise, and not smoking, to reduce your risk. Lifestyle changes can also help with managing psoriatic disease, improving treatment outcomes, and reducing complications.