What Causes Rare Diseases?

There are around 7000 rare diseases identified worldwide. In the US a rare disease is defined as one which affects less than 200,000 people. This amounts to around 30 million Americans affected by a rare disease. 

Some rare diseases are the result of a single gene mutation, often known as single gene disorders, their uncomplicated cause means a higher degree of accuracy in identifying them. 

Other rare diseases are the cause of chromosomal anomalies or changes – including microdeletion when a small piece of a chromosome is missing.

Some examples of rare diseases are the result of environmental or external factors. Fetal alcohol syndrome is a rare disease, caused by substance abuse on the part of the mother during pregnancy. 

The causes of rare diseases also include understanding more about how these genetic syndromes are inherited. This is because how a gene change is inherited can impact whether a rare disease will develop, or has a risk of developing within an individual. 

For example – autosomal recessive rare diseases are inherited when each parent passes on to their child a copy of a gene mutation. Children born to parents who are both carriers for an autosomal recessive disorder have a 25% chance of being born unaffected by a rare disease, or a 25% chance of being born affected by a rare disease. 

Other forms of inheritance that can cause a rare disease include autosomal dominant inheritance and x-linked inheritance. 

In some cases, a rare disease is caused by a de novo or new genetic mutation that can be predicted. This might occur at the time the reproductive cells, the egg and sperm, are being created, or during the initial development and growth of the fetus. 

Why is it important to understand the causes?

Improves the accuracy of genetic testing and diagnosis

The more we know about the specific causes of rare diseases, including the precise gene mutation that causes them, the more accurate genetic testing can be developed to diagnose them. 

Before the identification of the precise gene responsible for causing Fragile X syndrome, the FMR1 gene, genetic testing for the disease was not accurate. Now the exact genetic cause of the syndrome is known, testing is almost 99% accurate for diagnosing Fragile X syndrome. 

The more accurately we can diagnose rare diseases, the faster we can get the right care and support to rare disease patients. It reduces the time spent on long, stressful diagnostic journeys, and raises awareness about rare diseases as well. 

Understand more about how rare diseases are inherited

The more we understand how rare diseases are inherited, the better we can help families better understand family planning according to the potential for rare diseases in their children.

For some parents, who are carriers of specific genetic mutations inherited in a specific way, this might mean considering the risks involved, and the chances of their children developing a genetic syndrome, and then making the decision to plan a pregnancy or family planning around this. In some cases, egg or sperm donation may be necessary to reduce the risk of passing on a genetic syndrome, especially if that rare disease is known to be not compatible with life.

Tay-Sachs is a rare disease, the life expectancy of which is only a few years. Its prevalence is especially high among those of European Ashkenazi Jewish descent, and anyone with such a background would be advised to undergo carrier genetic screening before starting a family. 

Genetic counseling and rare disease causes

Genetic counseling is an important support tool that educates patients and families about the causes of rare diseases. They do so to help diagnose genetic syndromes and to help families understand both their genetic health and that of their children. 

Genetic counseling is instrumental in raising awareness about the causes of rare diseases and is helping to encourage more research into the causes of more diseases. This has the potential to benefit all rare disease patients and their families. 

Before consulting a genetic counselor, parents can utilize the Child Development Checker app as an invaluable resource. This app helps assess your child’s developmental and genetic concerns, offering early and accurate insights crucial for effective interventions. Additionally, the “Connect to an Expert” feature provides direct access to experienced genetic professionals for personalized guidance and support. Empower your child’s health management with the Child Development Checker app and connect with experts.