Most Common Genetic Disorders In Humans

The most common genetic disorders in humans include:

• Achondroplasia
• Cystic Fibrosis
• Down Syndrome
• Duchenne Muscular Dystrophy (DMD)
• Glucose-6 Phosphate Dehydrogenase (G6PD)
• Sickle Cell Anemia
• Thalassemia
• Hemochromatosis
• Myotonic Dystrophy
• Osteogenesis Imperfecta
• Polycystic Kidney Disease

These diseases can sometimes “skip” generations or lie dormant in that generation, but it may manifest in their offspring or their offspring’s offspring.

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 that can be passed down.

The Most Common Genetic Disorders

There are more than 6,000 genetic disorders. Below are some of the most common genetic diseases.

Achondroplasia

Achondroplasia is a common genetic condition marked by slow bone growth due to protein malfunction. A person with this condition may have the following:

• Shorter arms and legs 
• Large head with a prominent forehead and a flat nasal bridge
• Misaligned teeth
• Redundant skin folds on legs and arms

Inheritance Pattern

Achondroplasia is an autosomal dominant trait, meaning that just one copy of the mutated gene is enough to cause it to manifest.⁸

Prevalence

Achondroplasia is the most common mutation when it comes to stature. It occurs every one in 26,000-28,000 births.⁸

How to Prevent or Manage Achondroplasia

Achondroplasia is a disorder that can’t be cured, prevented, or treated. However, complications that may come with it can be addressed and managed.

Here are some treatments that may be administered or carried out for anyone suffering from complications from achodnroplasia:⁸

• Ventriculoperitoneal Shunting – Achondroplasia can often cause increased intracranial pressure due to excess cerebrospinal fluid, which can be painful. A cerebral shunt is used to divert fluid and reduce pressure.
• Decompression Surgery – This is necessary when achondroplasia causes craniocervical junction constriction, which may be dangerous for the spine and the brain.
• Weight Loss – This may be recommended for anyone with achondroplasia who is also suffering from sleep apnea. It may also be good to keep pressure off the joints.
• Growth Hormone Therapy – This can add a few more inches to a person’s short stature—but don’t expect too much growth. Some scientists also recommend doing this at a younger age, while others argue that people should wait until they’re old enough to make an informed decision.
• Spinal Surgery – This may be necessary for anyone with achondroplasia also suffering from kyphosis (a pronounced front-to-back curve of the spine) or spinal stenosis.
• Immunization – Because achondroplasia can increase respiratory risk, ensure that anyone with achondroplasia has all their immunizations covered.

To manage common challenges faced by those with achondroplasia, the following are recommended:⁸

• Environmental Modifications – Lowered light switches, access to stools or stepladders, and even pedal extenders may be necessary for those with achondroplasia, just so it isn’t difficult for them to carry out everyday tasks. Even workplace adjustments, such as smaller keyboards and easy restroom access, can help.
• Community – Achondroplasia may affect how much a person socializes, as some may find it difficult, especially considering how their peers may not fully understand their condition. Because of this, finding like-minded people or those with the same or similar conditions may help those with achondroplasia socialize. Not only is it good for them, but it can also give them a space to voice out their concerns, find information on employment or education, and give them a place to feel accepted.
• Monitoring of Development – Monitoring height, weight, head circumference, and even speech and language development can be a great way to spot whether or not achondroplasia will be significant in someone’s life. It can also prepare them to find ways to find specialists for speech or even decide on growth hormones if they choose. Surgery may also be necessary if height, weight, and head circumference are abnormal.
• Increased Protocols to Minimize the Risk of Spinal Injuries – Children with achondroplasia may be at higher risk of injury, so ensure that they aren’t playing too many high-contact sports at first while their spine is still in development.

Cystic Fibrosis

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.

Inheritance Pattern

Cystic fibrosis is an autosomal recessive disorder, which means two copies of the gene must be present for the disorder to manifest. This means that the parents, even if they carry the gene, may not show signs of it.⁹

Prevalence

Around 30,000 people in the United States have cystic fibrosis, with one in 30 people being carriers.¹⁰

How to Prevent or Manage Cystic Fibrosis

Because of advancements in cystic fibrosis research, treating and managing cystic fibrosis is possible.¹¹

To treat cystic fibrosis, you can opt for the following:¹¹

• Airway clearance therapy
• Mucus thinning medication
• Antibodies

Managing cystic fibrosis has also become easier. You can:

• Ensure you attend your check-ups regularly
• Regular bone and bone density tests
• Ultrasounds and respiratory cultures (if your doctor thinks it’s necessary)
• Proper hygiene
• Maintaining a healthy weight
• Exercise and a good diet

Down Syndrome

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:

• Flattened face
• Small head
• Short neck
• Protruding tongue
• Upward slanting eyelids
• Small ears
• Poor muscle tone
• Broad, short hands
• Short fingers
• Small hands and feet
• Excessive flexibility
• Tiny white spots on the colored part (iris) of the eye called Brushfield’s spots
• Short height

Inheritance Patterns

Most cases of Down syndrome aren’t inherited. More often than not, Down syndrome is caused by a random error during the cell division process.¹²

Prevalence

About one in every 700 people have Down Syndrome.¹³

How to Prevent or Manage Down Syndrome

There is no cure for Down Syndrome, but you can manage the symptoms and make adjustments to suit your lifestyle, like:¹³

• Speech therapy
• Physical therapy
• Community
• Special needs schooling
• Maintaining a healthy weight and eating a good diet

Duchenne Muscular Dystrophy (DMD)

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:

• Muscle weakness as early as two to three years of age
• Enlargement of the calves
• Waddling gait
• Lumbar lordosis or inward curving of the spine

Inheritance Patterns

DMD is X-linked recessive.¹⁴ This means that it’s only passed down via the X chromosome, and both parents need to be carriers.

Prevalence

Men are more likely to inherit DMD, with one in 3600 male infants inheriting the condition.¹⁴

How to Prevent or Manage DMD

There is no direct treatment for the condition itself, only managing and tackling the symptoms that come with it, like:¹⁴

• Glucocorticoid Therapy – A therapy that helps improve muscle function by decelerating skeletal muscle necrosis
• Routine Heart Tests – Staying on top of heart health is particularly important for those with DMD, so monitoring heart tests is necessary to determine phases of cardiomyopathy and what can be done about them
• Doctor-approved Orthopedic Intervention – Certain exercises and stretches will be recommended by your doctor to encourage muscle strength and help avoid discomfort or degeneration
• Good Hygiene, Nutrition, and Exercise – Overall health benefits from a balanced diet, cleanliness, and regular exercise

Glucose-6 Phosphate Dehydrogenase (G6PD)

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. 

Inheritance Patterns

G6PD is X-linked recessive, meaning that men manifest the trait and women are more often carriers.¹⁵

Prevalence

While rare, G6PD mostly affects African American populations in America and those who live in more tropical areas. It’s said to affect around 400 million people worldwide.¹⁶

How to Prevent or Manage G6PD

In most cases, G6PD only becomes a problem when you’re exposed to trigger foods or medicines, so avoidance is key. ¹⁵ You will also need to inform all your healthcare providers of what you’re avoiding so that the G6PD isn’t triggered.

Sickle Cell 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 sickles. These sickle cells are often sticky and rigid, blocking blood flow.

Inheritance Patterns

Sickle cell anemia is an autosomal recessive disorder, which means two copies of the gene must be present in offspring to manifest.¹⁷

Prevalence

There are fewer than 200,000 people in the United States with sickle cell anemia.¹⁷

How to Prevent or Manage Sickle Cell Anemia

Sickle cell anemia can be tricky to manage but not impossible. Here are some of the most widely available treatments and management options:¹⁸

• Bone Marrow Transplant – These transplants are your best bet, as they will fully replace your bone marrow, which is generating “faulty,” sickle-shaped blood cells. Replacing the marrow with one that can create healthy red blood cells is the most straightforward option.
• A Variety of Medications – Medications like Voxelotor can prevent red blood cells from forming into the sickle shape, while others can help curb pain, prevent inflammation, and keep cells from sticking to blood vessel walls.
• Blood Transfusions – These can help with anemia prevention, as well as curb the possibility of complications before any surgeries.

Thalassemia

Thalassemia is an inherited blood disorder. It affects your hemoglobin genes, affecting your body’s ability to generate healthy RBCs. 

Symptoms may include:

• Severe anemia
• Fatigue
• Weakness
• Pale or yellowish skin
• Deformities in the facial bones
• Swelling of the abdomen
• Darkly-colored urine

Inheritance Patterns

Thalassemia is an autosomal recessive disorder, which means two copies of the gene must be present in offspring to manifest.¹⁹

Prevalence

Thalassemia is more common in Southeast Asia or in those of Southeast Asian descent. In the United States, up to 5% of people have the gene, with a little less than half being carriers only.²⁰

How to Prevent or Manage Thalassemia

Similar to sickle cell anemia, some of the more straightforward treatment and management options have to do with transfusions and, sometimes, even transplants. Here are some of them:²¹

• Blood Transfusion – Having a regular source of healthy red blood cells is important, especially for those with more severe Thalassemia.
• Iron Chelation Therapy – Regular blood transfusions can cause a build-up of iron in the body, which can be bad for the heart and liver. This treatment removes excess iron to keep the organs functioning even when receiving several transfusions.
• Folic Acid Supplements – Folic acid strengthens and helps build healthy red blood cells. Taking supplements may give your blood cells a boost.
• Bone Marrow Transplant – This ensures that the source of your red blood cells is healthy and can produce proper cells. It will replace your current bone marrow and create healthy cells.

Hemochromatosis

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:

• Cirrhosis or liver damage
• Liver cancer
• Heart problems
• Arthritis or joint pain
• Diabetes

Inheritance Patterns

Hemochromatosis is an autosomal recessive disorder, which means two copies of the gene must be present in offspring to manifest.²²

Prevalence

In the United States, about one in 300 white people have hemochromatosis, with a lower percentage observed in people of color.²²

How to Prevent or Manage Hemochromatosis

Managing hemochromatosis can be done by doing the following:²²

• Blood Removal – Similar to donating or giving blood, a needle is inserted into a vein and used to drain a small amount of blood. This is necessary to help your body remove excess iron.
• Regular Blood Tests – Blood tests will help you monitor your iron levels, alerting you when your iron levels are abnormal.
• Iron Chelation Therapy – This treatment helps remove excess iron in your blood and body. It binds the iron and assists the body in expelling it.
• Balanced Diet and Exercise – A good diet that limits iron consumption is great overall, as well as regular exercise.
• Avoiding Alcohol – Alcohol can cause liver damage, which can aggravate hemochromatosis.

Myotonic Dystrophy

Myotonic Dystrophy is a form of muscular dystrophy. It causes progressive muscle weakness and decline.

Symptoms of myotonic dystrophy include:

• Difficulty letting go of one’s grip (myotonia)
• Weakness of muscles in the hands and feet
• Difficulty swallowing
• Abnormal heart rhythms

Inheritance Patterns

Myotonic Dystrophy is an autosomal dominant disorder, meaning just one copy of the mutated or abnormal allele is enough for you to be at risk.²³

Prevalence

There are about ten cases of myotonic dystrophy in every 100,000 people.²³ It’s more common in those with European ancestry.

How to Prevent or Manage Myotonic Dystrophy

There is no direct treatment for myotonic dystrophy, just ways you can manage your symptoms. You can opt for any of the following:²³

• Respiratory Pump Machines – Breathing assistance throughout the night can be beneficial, especially via machines with detachable face masks.
• Cataract Surveillance – Cataracts are common in those with myotonic dystrophy, so make sure to monitor your eyes for any. You can get them removed with surgery.
• Monitoring for Behavioral Abnormalities – Those with myotonic dystrophy may often develop some behavioral problems and learning deficiencies. Special education and counseling can be helpful.
• Various Medications – Several medications can help with heart problems, insulin resistance, and even trouble with grip that can arise from myotonic dystrophy.

Take note that those with myotonic dystrophy may not react well to general anesthesia. Remind any surgeon or healthcare provider of your myotonic dystrophy if you’re getting any surgery done.

Osteogenesis Imperfecta

Osteogenesis Imperfecta is a genetic disorder present at birth or congenital. It is also known as brittle bone disorder. 

A person born with this disorder may have weak, easily fractured, or abnormally formed bones.

Inheritance Patterns

Osteogenesis Imperfecta is an autosomal dominant disorder, which means just one copy of the mutated or abnormal allele is enough for you to be at risk.²⁴

Prevalence

Osteogenesis Imperfecta occurs in one in 20,000 people, pretty evenly across gender and race.²⁴

How to Prevent or Manage Osteogenesis Imperfecta

There is currently no cure for Osteogenesis Imperfecta. You can try the following to manage the symptoms:²⁴

• Physical Therapy – This is done to minimize fractures and disabilities and to strengthen muscles
• Counseling – For any emotional or mental toll the disorder may take
• Regular Check-ups – Do these with all the doctors involved, from your geneticist to orthopedists
• Intramedullary Rodding – This treatment deals with inserting rods into the bones for strength and leg positioning

Polycystic Kidney Disease

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.

Inheritance Patterns

There are two types of PKD: Dominant and Recessive. As the name implies, dominant polycystic kidney disease is an autosomal dominant disorder, meaning that just one copy of the mutated or abnormal allele is enough for you to be at risk.²⁵ Recessive polycystic kidney disease is autosomal recessive, meaning two corrupted copies are necessary for it to manifest.

Prevalence

The dominant version is more prevalent, affecting one in 500 to 1,000 people. The recessive version only affects one in 20,000 to 40,000 people.

How to Prevent or Manage Polycystic Kidney Disease

There is no cure for PKD, but ways to manage it:²⁵

• Antihypertensive Medication – People with PKD often develop hypertension (usually one of the first signs). Keeping it at bay is for the best.
• Dialysis – This helps your kidney filter waste products much more efficiently, usually done for those who may not be eligible for a full renal transplant just yet.
• Renal Transplant – The diseased kidney/s is/are replaced by a healthy one or healthy set of kidneys to ensure better function.
• Avoid Caffeine, Smoking, and Alcohol – These vices can significantly damage the kidneys and affect function.
• Antibiotics for UTIs – UTIs are common in those with PKD, so taking antibiotics for them when the need arises is important.

What are 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.

Types of Genetic Disorders

Scientists group genetic disorders into three main categories. The cause or location of the defect determines them.

Single-Gene Disorders 

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: 

• Autosomal dominant disorders happen when a person has only one altered copy of the applicable gene. The other copy remains normal.
• Autosomal recessive disorders occur when a person has two altered versions of the applicable gene.
• X-linked disorders occur when a defective gene is present on the X chromosome. They often affect males since they possess only one X chromosome. 

Chromosomal Disorders

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.

Complex Disorders 

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. 

How are Genetic Disorders Diagnosed?

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: 

• Magnetic resonance imaging (MRI)
• Computerized tomography (CT) scans
• X-rays 

Medical History

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.

You may share your test results with your doctor if you have undergone genetic testing before. It can give them further insights into your health history.

Family 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.

Laboratory Testing

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

• Cytogenetic testing — used to detect structural defects in chromosomes
• Biochemical testing — used to test protein functions
• Molecular testing —  detects defects in DNA sequencing

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.

When Are Genetic Disorders Diagnosed?

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.