How likely am I to inherit a rare disease?

What Are Rare Diseases?

A rare disease refers to a disease that only affects a small number of people. Also called “orphan diseases” most are rare genetic diseases that are present, though not necessarily symptomatic, from birth.

A disease affecting less than 200,000 people is considered a rare disease in the United States.

This definition and “orphan disease” nickname come from the Orphan Drug Act of 1983, which was passed by Congress to incentivize pharmaceutical companies to create drugs to treat these diseases. They were referred to as “orphans” as no medical company was willing to adopt them and research a cure because too few were affected to be profitable.

Rare diseases are often progressive, chronic, degenerative and life threatening. Many are disabling and patients often lose autonomy in their lives, which compromises their quality of life.

Rare diseases often come with much pain and suffering, affecting both the patient and their family.

Most often, rare diseases do not have a cure. There are about 6,000 to 8,000 rare diseases on record, 75% of which affect children and 85% of which are genetic. The remaining 15% are derived from viral or bacterial infections, environment or allergies or are proliferative or degenerative.

The Genetics of Rare Diseases

Most rare diseases are inherited human diseases, meaning they are genetically passed down. With monikers like Wolman Disease and Rett Syndrome, they are much more rare and unknown than common genetic disorders you’ve likely heard of, such as Lupus or Celiac Disease.

Genetic rare diseases are the result of changes in chromosome of genes. Certain rare diseases are passed down genetically. In other cases, a person may randomly present a rare disease and be the first in their family to experience it.

How Genetic Disorders Are Inherited

But what causes genetic disorders? A mutation in the genes is to blame for genetic disorders. The mutation is often passed down from parents at the time of conception. The chances of a child will contract the rare disease is determined by patterns of inheritance.

Two patterns predict the probability that someone will inherit a genetic disorder. These patterns don’t necessarily guarantee the genetic mutation will be inherited, but the likelihood is high.

The first pattern is based on genetics, which is a predictor for diseases like breast cancer and most autoimmune diseases. The second is around genetic mutations, as is the case with diseases like hemophilia.

Diseases deriving from mutation will present with varying degrees of severity.

Risk of genetic inheritance in humans is based on two things. The first is how many copies—one or two—of the mutated gene are inherited.

In other words, is the gene mutation received from one or both parents? Both parents passing on a gene mutation is one of the causes of genetic disorders in pregnancy.

The second being whether or not the genetic mutation is located in the X or Y sex chromosomes or one of the 22 other non-sex chromosome pairs. Based on the combination of characteristics, disorders are classified as:

• X-linked dominant
• X-linked recessive
• Autosomal dominant inheritance
• Autosomal recessive
• Codominant
• Mitochondrial

These patterns of inheritance mean the question becomes, “How is a dominant genetic disease inherited?” or “How is a recessive gene inherited?” versus the blanket question of, “How is a genetic disorder passed down?”

Percentage of People With Rare Diseases

You may be wondering just how many people experience a rare disease.

We know a disease is considered rare when less than 200,000 people have it, but with 6,000 to 8,000 different kinds, the exposure is significant. In fact, rare disease statistics tell us that about 1 in 10 people in the United States—that’s 30 million Americans—have a rare disease.

If a Genetic Disorder Runs in my Family, How Likely Am I To Inherit a Rare Disease?

If a genetic disorder runs in your family, the first thing you likely want to know is how likely it is that you will experience the same disease. It’s important to know that many factors influence whether someone has a genetic disorder.

How the disorder is inherited is perhaps the most important piece of information in understanding how likely you are to inherit it.

X-linked dominant inheritance

The odds of passing on X-linked genes vary between women and men since women carry two X chromosomes and men only have one. If your father has an X-linked dominant disorder and you are male, you will not be affected.

If you are female, you will definitely inherit the disorder. If your mother has an X-linked dominant disorder, there is a 50 percent chance she has passed it down to you, whether male or female.

X-linked recessive inheritance

Men who have a father with an X-linked recessive disorder will not inherit the disorder. Women will carry of single copy of the mutated gene if their father has the disorder.

If you mother has an X-linked recessive disorder, there is a 50 percent chance you will have the disorder if you are male and a 50 percent chance of carrying the gene if you’re a female.

Autosomal dominant inheritance

You have a 50 percent chance of getting an autosomal dominant genetic disorder if one of your parents has one.

Autosomal recessive inheritance

If both of your parents do not have an autosomal recessive disorder but carry the gene for it, you have a 25 percent chance of inheriting it. There is a 50 percent chance you are a carrier for it.

Codominant inheritance

Codominant inheritance refers to both parents passing down a different version of a certain gene, which in turn both affect the inherited trait. The chances of passing down a codominantly inherited disorder is impossible to predict as it all depends what version of the gene is passed along.

Mitochondrial inheritance

All mitochondria, the center of a cell that produces energy, contain some DNA. Mutations in the mitochondrial DNA lead to genetic disorders. Men and woman can both be affected by these disorders, but only mothers can be carriers for them.

If you mother has a mitochondrial disorder, you will definitely inherit the disorder. But if your father has it, you will not.

What Are the Chances That my Children Will Inherit a Rare Disease?

Genetic disorders in children present themselves via the same inheritance patterns as your parents passing them on to you—X-linked dominant, X-linked recessive, autosomal dominant inheritance, autosomal recessive, codominant, mitochondrial.

See the rates for passing on genetic disorders by inheritance pattern in the section above (If a Genetic Disorder Runs in my Family, How Likely Am I To Inherit a Rare Disease?) for information on parents passing on genetic disorders to children.

Are Genetic Disorders Preventable?

The prevention of genetic disorders is a tricky thing, which cannot be done without the help of science. Since genetic disorders are inherited, prevention has to occur before conception.

Couples who use IVF with genetic testing can determine which embryos do and, more importantly, do not carry the genes or mutations that lead to certain genetic disorders. Some genetic testing can be done on embryos to determine if a pregnancy may be terminated early on because a genetic issue is found. Preventing genetic disorders naturally is not possible.

Diagnosis of Rare Diseases

Diagnosing a rare disease can be difficult. While some are simple to find through rare disease testing on DNA, others are not as black and white.

Many rare diseases go on as undiagnosed conditions for long periods of time as patients rule out issues through experimenting with treatments. Some people go their whole lives without getting a specific diagnosis for their rare disease.

Genetic Testing for Rare Diseases

Genetic testing for diseases and disorders, also known as DNA testing, is the most common tool to test for rare diseases. Not all rare diseases will show up on this kind of test, but genetic tests have been created to detect thousands of diseases.

Most tests examine single genes to detect genetic disorders. Others look for inherited genetic mutations.

Treatment and Management of Rare Diseases

With thousands of rare diseases, the treat and management of a rare disease is about as far from one-size-fits-all as you can get. With rare diseases, doctors are often fairly in the dark on how to manage and treat them as well.

It’s important for all patients to be their own advocates but arguably even more so for people with a rare disease. In general, rare diseases are never “healed” or “cured” and certainly do not go away, but there is hope to find levels of treatment and management to improve quality of life with a rare disease.

Where to Find Help and Resources for Rare Disease Patients

The National Organization for Rare Disorders is a great resource for rare diseases. The Genetic and Rare Disease Information Center keeps a list of opportunities to get government funding for rare diseases as well as support groups to assist family members in providing help for children with rare diseases. Orphanet offers a list of rare diseases by prevalence.

Genetic Counselors

A genetic counselor is a healthcare professional who is trained to help patients and their families understand genetic disorders. They provide information and support and sometimes serve as advocates on behalf of the patient by referring them to services and resources to assist them.

Misconceptions About Living With a Rare Disease

What it means to live with a rare disease is different for everyone. Rare diseases come in all kinds of forms with a plethora of symptoms—no two experiences are alike.

Since rare diseases are so uncommon, there is a lot of misconception surrounding them. Here are a few:

Doctors give rare diseases lots of attention

Many people with a rare disease feel very alone in their treatment. Because rare diseases show up infrequently, they are not top of mind for doctors and researchers and do not get a lot of attention.

Individuals with rare diseases must advocate extra hard on their behalf to get the attention they need.

Rare diseases “heal” “go away,” or get “cured”

While it’s polite to wish people well, it can be a frustrating gesture for people experiencing a rare disease. Most rare diseases are genetically linked and with a person for their whole lives.

Rare diseases may be managed or stabilized, but never go away completely. Receiving treatment for a rare disease, even when successful, does not mean someone is cured. Rare diseases are a lifelong condition.

Care for rare diseases is covered by insurance

Many make the assumption that individuals with rare diseases are afforded medical treatment through their insurance. This is simply not always the case.

Treatments for rare diseases can be hard to come by and extremely expensive, even with health insurance.

Life can’t be enjoyed if you’re in pain

Some rare diseases cause chronic and sometimes never-ending pain. A person may be in physical pain, but still able to smile and laugh.

Feeling and expressing happy emotions doesn’t mean the pain goes away. And it doesn’t mean that person is “cured.”

A rare disease is an excuse to be lazy

It’s common for individuals with debilitating rare diseases to be unable to work and spend a lot of time at home. Managing a rare disease can feel like a full time job.

The misconception that people have given up or don’t have the will to push through is completely unfair.

Doctors have what it takes to help people with rare diseases

Oftentimes doctors only know as much about a rare disease as a person shares with them. They are often learning alongside the patient as he or she seeks treatment.

All rare diseases are visible

Not all disabilities are visible and neither are rare diseases. Assuming someone is ok because he or she “looks fine” is a bad assessment. Chances are you encounter people with rare diseases quite often and have no idea how they are feeling.

People living with a rare disease miss out on a joyful life

Rare diseases highly influence people’s live, but having a rare disease is not a deal breaker for living a joyful life. Many people with a rare disease lead happy lives filled with reaching goals, fostering relationships and doing things they love.

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