In This Article
In This Article
The human genome, or the complete set of DNA in each of our cells, is complex. While a DNA molecule contains instructions on a person’s growth and development, the human genome is subject to changes.1,2
The changes in the human genome can affect molecules that make up the DNA or even chromosomes. They can lead to genetic disorders.
Genetic disorders are conditions caused by gene mutations or changes in a person’s typical DNA sequence.3
DNA mutations may arise due to errors in DNA replication. Environmental factors, such as radiation exposure and cigarette smoking, can also cause gene changes.
DNA contains genetic material. It supplies the code for making proteins that allow the body to perform its functions.
When a change occurs in a part of the DNA, the process of protein-coding is affected. As a result, some bodily functions are also affected.
The impact of DNA changes depends on where the mutations occurred.
Some mutations will have little to no effect. Others can completely alter the body’s cell biology, causing genetic disorders.
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Scientists group genetic disorders into three main categories. The cause or location of the defect determines them.
Single-gene disorders are defects from a mutation in one particular gene. These disorders are often passed down in simple, straightforward ways and can be caused by just a single gene.4
Single-gene disorders are further classified into three types:
Chromosomal disorders are genetic diseases that result from changes in the chromosomes. They are also called chromosomal abnormalities.5
Chromosomes are thread-like structures within a cell’s nucleus or center. Each chromosome has a single DNA molecule tightly wrapped around proteins.
Their primary role is to ensure that the DNA is accurately replicated and distributed during cell division. We each have 23 pairs of chromosomes.
However, an affected person can have extra chromosomes in some chromosomal disorders. An example is Down’s syndrome (or Down syndrome), where a person has an excess copy of chromosome 21.
These are also known as multifactorial inheritance.
Complex disorders are caused by changes that occur in multiple genes. Often, these result from a complex interaction between lifestyle and other external factors.6
Scientists consider cancer to be a complex disorder.
There are more than 6,000 genetic disorders. Below are some of the most common genetic diseases.
Achondroplasia is a common genetic condition marked by slow bone growth due to protein malfunction. A person with this condition may have the following:
Cystic fibrosis is a genetic condition that causes your body to produce thick, sticky mucus. It also affects the secretion of other fluids like sweat and digestive juices.
If you have the cystic fibrosis gene, you may begin to have difficulty breathing as you grow older. The mucus buildup can block your airways.
Down’s syndrome (or down syndrome) is a chromosomal defect that occurs when there’s an extra copy of chromosome 21. It can result in mental disability and delays in development.
A person with down syndrome usually possesses these facial and physical features:
Duchenne Muscular Dystrophy (DMD) is a genetic condition marked by a continuous decline of the muscles. It is caused by mutations in the protein that keeps the muscles intact.
Symptoms of DMD may include:
Glucose-6 Phosphate Dehydrogenase (G6PD) is a genetic condition. The lack of the glucose-6 phosphate dehydrogenase enzyme in your body marks it.
This enzyme helps with the proper function of the red blood cells. An insufficient G6PD enzyme can shorten red blood cells’ lifespan and may lead to hemolytic anemia.
Sickle Cell Anemia is a lifelong condition that can be inherited from both parents. It is a form of sickle cell disease. It affects the structure of your red blood cells (RBCs).
Normal RBCs are round and flexible, allowing them to easily move around the blood vessels. People with sickle cell anemia have deformed RBCs.
Some of their RBCs are shaped like a sickle. These sickle cells are often sticky and rigid, blocking blood flow.
Thalassemia is an inherited blood disorder. It affects your hemoglobin genes, affecting your body’s ability to generate healthy RBCs.
Symptoms may include:
Hemochromatosis is a disorder that causes excessive iron buildup in your body organs. It's also called iron overload. It occurs when the body absorbs too much iron.
Excessive levels of iron are toxic to your body and may cause serious health problems, such as:
Myotonic Dystrophy is a form of muscular dystrophy. It causes progressive muscle weakness and decline.
Symptoms of myotonic dystrophy include:
Osteogenesis Imperfecta is a genetic disorder present at birth or congenital. It is also known as brittle bones disorder.
A person born with this disorder may have weak, easily-fractured, or abnormally formed bones.
Polycystic Kidney Disease (PKD) occurs when numerous cysts grow in your kidney. These clusters or cysts are non-cancerous but are filled with fluid.
They can cause kidney swelling. Over time, they can affect your kidney’s normal function.
A genetic diagnosis is determined through several approaches.
Physical Examination
During a physical exam, a geneticist will conduct a thorough assessment. It may involve measuring distances between eyes, length of limbs, and head circumference.
This is because some genetic disorders are linked to distinct physical traits. Sometimes, facial features can suggest the presence of a genetic condition. Eye exams and neural exams are also performed.
Imaging studies may be used to get a picture of the structures found inside the body, such as:
A person’s medical history provides valuable insights into their health and well-being.
Including past and current health issues, medications, and allergies are all essential.
If you have undergone genetic testing before, you may share your test results with your doctor. It can give them further insights into your health history.
Genetic conditions are often passed down from generation to generation. Information regarding the health of family members is crucial. Family history can provide helpful insights in diagnosing conditions caused by mutations in the DNA.
Genetic counselors or doctors may ask about the health conditions of those closely related to you. These include your parents, siblings, children, and other close family members.
The information they obtain may reveal valuable clues. For example, they can learn the inheritance pattern of a genetic disorder that could potentially run in the family.
Lab tests, such as genetic testing, are used to diagnose genetic disorders. Several types of genetic tests can be used to diagnose a genetic disorder, including:7
Many genetic conditions can now be tested using a screening test and genetic testing. Some examples are newborn screenings and prenatal testing.
But in some conditions where no genetic test is available, it may help sequence the entire genome. Doing this can help locate the genetic variant responsible for the condition.
You can be diagnosed with a genetic disorder at any time within your lifetime. Some features of genetic conditions often appear very early or too late, so it’s essential to keep these tests in mind. The availability of testing may also affect diagnoses.
A diagnosis is very important, even if there’s currently no treatment available. This can help manage expectations and identify advocacy resources and proper support.
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