Inherited Diseases: Which Conditions Can Be Passed Down Through Your Family?

"My father has Thalassemia. Will I have it too?"

"My baby was diagnosed with G6PD deficiency. Is it inherited?"

"My aunt had breast cancer because of the BRCA gene. Should I get tested?"

These are common questions that many people ask, especially when planning a family or after learning that a relative has been diagnosed with a genetic condition.

The truth is that not every disease is inherited, but some conditions can be passed from parents to their children through genes.

Understanding inherited diseases allows individuals and families to make informed healthcare decisions, seek appropriate screening, and take preventive measures before symptoms appear.

In this article, we'll explain what inherited diseases are, how they are passed down, common examples, and when you should consider genetic testing.

 

What Are Inherited Diseases?

Inherited diseases, also known as hereditary diseases, are medical conditions caused by changes (mutations) in genes that are passed from parents to their children.

Genes act as the body's instruction manual. They determine characteristics such as eye colour, blood type, and many aspects of how our bodies function.

Sometimes, a gene contains a mutation that affects how the body develops or works. This mutation can be inherited, increasing the likelihood of certain medical conditions.

Not everyone who inherits a genetic mutation will develop a disease. Some people become carriers, meaning they carry the altered gene but do not experience any symptoms. However, they may still pass the gene on to their children.

 

Inherited Diseases vs Family History: What's the Difference?

Many people assume that any disease running in the family is inherited, but that's not always true.

There is an important distinction between inherited diseases and diseases with a family history.

Inherited Diseases

These are directly caused by changes in genes that are passed from parents to children.

Examples include:

• Thalassemia
• G6PD Deficiency
• Hemophilia
• Spinal Muscular Atrophy (SMA)
• Cystic Fibrosis

Diseases Influenced by Family History

Conditions such as diabetes, high blood pressure, heart disease, and some cancers may occur more frequently in families because of a combination of genetics, shared lifestyle, and environmental factors.

Having a family history increases your risk but does not guarantee that you will develop the disease.

 

How Are Genetic Diseases Passed Down?

Every person inherits one copy of each gene from their mother and one from their father.

Depending on the condition, inherited diseases may follow different inheritance patterns.

The most common include:

1. Autosomal Recessive Inheritance

A child must inherit the faulty gene from both parents to develop the disease.

If both parents are carriers:

• 25% chance the child is affected
• 50% chance the child is also a carrier
• 25% chance the child inherits neither faulty gene

Thalassemia is one of the best-known examples.

2. X-linked Inheritance

Certain diseases are carried on the X chromosome.

These conditions often affect males more severely because males have only one X chromosome.

Hemophilia and some forms of G6PD deficiency follow this inheritance pattern.

3. Autosomal Dominant Inheritance

Only one copy of the altered gene is needed for a person to develop the disease.

Examples include:

• Huntington's disease
• Familial Hypercholesterolemia

 

Common Inherited Diseases

1. Thalassemia

Thalassemia is one of the most common inherited blood disorders in Malaysia.

It affects the body's ability to produce healthy haemoglobin, leading to anaemia.

Symptoms may include:

• Persistent tiredness
• Pale skin
• Delayed growth in children
• Enlarged spleen

Many individuals are Thalassemia carriers and remain healthy without symptoms. However, if both parents are carriers, there is a risk of having a child with severe Thalassemia.

2. G6PD Deficiency

G6PD deficiency is an inherited enzyme disorder that affects red blood cells.

Most individuals live normal lives, but exposure to certain medications, foods (such as fava beans), or infections may trigger the destruction of red blood cells (haemolysis).

In Malaysia, newborn babies are routinely screened for G6PD deficiency because early diagnosis helps prevent complications.

3. Hemophilia

Hemophilia is a genetic bleeding disorder where the blood does not clot normally.

People with Hemophilia may experience:

• Prolonged bleeding after injuries
• Easy bruising
• Bleeding into joints

The condition mainly affects males and is usually inherited through the mother's X chromosome.

4. Spinal Muscular Atrophy (SMA)

SMA is a rare inherited condition that affects the nerves controlling muscle movement.

Symptoms often begin during infancy or childhood and may include:

• Muscle weakness
• Difficulty sitting or walking
• Problems swallowing or breathing

Carrier screening can identify couples at risk of having a child with SMA.

5. Familial Hypercholesterolemia (FH)

Familial Hypercholesterolemia is an inherited condition that causes extremely high cholesterol levels from birth.

Without treatment, affected individuals have a much higher risk of developing heart disease at a young age.

Unlike lifestyle-related high cholesterol, FH requires lifelong medical management.

6. BRCA Gene Mutations

Mutations in the BRCA1 and BRCA2 genes significantly increase the risk of breast and ovarian cancer.

Not everyone carrying a BRCA mutation will develop cancer, but knowing your genetic status allows doctors to recommend appropriate screening and preventive strategies.

 

Who Should Consider Genetic Testing?

Genetic testing may be recommended if:

• You have a family history of inherited diseases.
• You or your partner are planning to have children.
• A previous child has been diagnosed with a genetic disorder.
• Multiple family members have the same medical condition.
• There is a strong family history of early-onset cancers.
• You have experienced recurrent miscarriages.
• You belong to an ethnic group with a higher prevalence of certain inherited conditions, such as Thalassemia.

 

Why Is Genetic Screening Important Before Pregnancy?

Many inherited diseases can be passed to children even when both parents appear healthy.

Carrier screening before pregnancy helps couples understand their genetic risks and allows them to make informed reproductive decisions.

Early awareness supports better pregnancy planning and healthcare management.

Can Inherited Diseases Be Prevented?

Genes cannot be changed, but knowledge can make a difference.

While inherited diseases cannot always be prevented, early identification allows:

• Better disease management
• Earlier treatment
• Personalised health monitoring
• Informed family planning
• Reduced complications
• Appropriate lifestyle modifications

For many hereditary conditions, early diagnosis leads to significantly better health outcomes.

 

Frequently Asked Questions (FAQ)

Q1: If my parent has an inherited disease, will I definitely have it?

Not necessarily. Your risk depends on the specific condition and how it is inherited. Some people inherit the altered gene but become carriers without developing symptoms.

Q2: Is Thalassemia contagious?

No. Thalassemia is an inherited blood disorder and cannot be spread through physical contact, food, or air.

Q3: Should couples undergo genetic screening before marriage or pregnancy?

Genetic screening is particularly valuable for couples with a family history of inherited diseases or those from populations where certain genetic conditions are more common. It helps identify carrier status and supports informed family planning.

Q4: What's the difference between genetic testing and a health screening?

Health screening evaluates your current health and looks for early signs of disease, such as diabetes, high cholesterol, or liver problems. Genetic testing analyses your DNA to identify inherited conditions or genetic risks that may affect you or your future children.

 

Understanding Your Genes Is the First Step Towards Better Health

Your genes are a part of your health story, but they do not determine your future.

Understanding inherited diseases empowers you to take proactive steps through early screening, informed family planning, and personalised healthcare. Whether you are planning to start a family, have a known family history of genetic conditions, or simply want to better understand your health risks, timely assessment can make a meaningful difference.

At Prinz Klinik, we are committed to preventive healthcare through comprehensive health screening and selected genetic testing services. Our experienced doctors provide personalised consultations to help you understand your family history, interpret your risks, and recommend appropriate screening options based on your individual needs.

Taking action today can help protect not only your own health but also the health of future generations.