How genetic testing can tell you more about rare disease

Rare diseases

Most diseases have at least some genetic component to them. Many of the more common ones like cancer, dementia, heart disease, and diabetes are usually caused by a complex interplay of a person’s DNA, lifestyle, and environment. But certain conditions—often referred to as “rare” genetic diseases—are 100% (or nearly 100%) caused by genetics. In fact, current estimates suggest there are possibly thousands of such conditions.

By definition, no one rare genetic disease is common—but taken as a group, these types of diseases are not as uncommon as you might think. Even if only a few thousand people have any one rare genetic disease, when you take these diseases as a whole, a sizable part of the world’s population is affected. In fact, as many as 10% of Americans have such a condition.

Luckily, some of these conditions are treatable. Treatment of a rare disease can involve therapeutics or, in some cases, simple lifestyle changes. Take phenylketonuria (PKU), for instance, which is a genetic disease that can be managed simply with a change in diet to avoid foods with phenylalanine. Other diseases, like congenital asplenia—a condition in which an individual is born without a spleen—require continued monitoring to ensure that individuals are taking antibiotics, getting vaccinated to prevent infections, and even getting medical advice for common infections like the flu. For individuals whose rare disease is considered incurable, there may be clinical trials looking for a cure.

With any rare disease, having the right support—and the right knowledge—is key. Many genetic diseases are identified at birth, but some can also present themselves later in life. This means that some people have a disease-causing gene variant, but haven’t yet experienced any symptoms. In these cases, predictive genetic testing can attempt to detect the gene variant before the disease appears. Knowing that you’re predisposed to develop a genetic disorder may help inform your lifestyle and healthcare decisions. (Additionally, carrier screening is a form of genetic testing that can determine a couple’s risk of passing on a disease-causing gene variant to their children.)

Though genetic testing is evolving rapidly, it still has its limits. For example, it can determine if someone has a gene variant linked to a certain disease, though scientists can’t currently say with 100% accuracy how most variants will affect the body. Also, there are cases where a disease is known to be genetic, but the gene causing it hasn’t been identified yet. Testing can, however, often give you key insights that lead to better outcomes with the help of a healthcare professional.

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