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Most Common Genetic Disorders In Humans
Updated on November 15, 2023
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Most Common Genetic Disorders In Humans

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.

Most Common Genetic Disorders In Humans 2

The Most Common Genetic Disorders

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:

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

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.

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

Duchenne Muscular Dystrophy

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

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.  

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 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:

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


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

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

Osteogenesis Imperfecta

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

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.

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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.

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.

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.

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.

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Updated on November 15, 2023
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7 sources cited
Updated on November 15, 2023
  1. Deoxyribonucleic Acid (DNA).” National Human Genome Research Institute.
  2. Our Genome Changes Over Lifetime, And May Explain Many 'Late-onset' Diseases.” Science Daily.
  3. Genetic Disorders.” National Human Genome Research Institute.
  4. Single Gene Disorders.” University of Utah.
  5. Genetic Disorders.” Cleveland Clinic.
  6. Medical Genetics: Multifactorial Inheritance.” University of Rochester Medical University.
  7. Understanding Genetics: A District of Columbia Guide for Patients and Health Professionals.” National Center for Biotechnology Information.
Dr. Dhingra
Dr. Harshi Dhingra
Medical Reviewer
Dr Harshi Dhingra is a licensed medical doctor with a specialization in Pathology. Dr. Dhingra has of over a decade in diagnostic, clinical, research and teaching work, including managing all sections of Pathology laboratory including histopathology, cytology, hematology and clinical Pathology.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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