5 Things to Know About Rare Diseases and Genetic Testing - Dr Anup Rawool

The World Health Organization (WHO) defines a rare disease as one that affects fewer than 65 individuals per 100,000 people. While different countries may classify rare diseases differently based on their unique population demographics, healthcare systems, and available resources, this remains the widely accepted standard definition.

Globally, there are an estimated 7,000 to 8,000 rare diseases, with approximately 450 rare diseases officially recorded in India across tertiary hospitals. This indicates that around 60 million people in India are living with rare diseases.

Here are five key insights into rare diseases and the crucial role of genetic counselling in their diagnosis and treatment:

1. Rare diseases are heterogeneous in terms of signs, symptoms, and origin

Rare diseases are characterised by highly variable and complex signs and symptoms. Even different individuals with the same disease can experience different symptoms, ranging from mild to severe, with slow or rapid progression.

Rare diseases are predominantly genetically driven, although they can also result from bacterial or viral infections, or environmental factors. This variability makes diagnosing rare diseases challenging, often requiring advanced technologies, such as genomics, to identify genetic mutations and provide accurate diagnosis.

2. Family history can hold genetic clues for rare disease diagnosis

Family history is a critical factor in understanding the origin and inheritance patterns of rare diseases. Sharing your family's medical history with your doctor can help identify potential risks and inform the need to take genetic testing and counselling.

Early diagnosis and intervention can significantly improve outcomes for individuals affected by rare diseases.

3. Genetic insights on rare diseases can personalise further treatment

Genetic testing can pinpoint the specific gene mutation responsible for a rare disease, providing valuable information to personalise treatment strategies.

While a cure may not be available for all rare diseases, treatment options are not always prohibitively expensive. For example, some conditions may require affordable medications, such as Vitamin B12, which the patient may need to take long-term.

However, identifying the most effective treatment requires knowing the specific genetic mutation, which can only be determined through genetic testing. This makes genetic testing essential for selecting the right therapy for each patient.

4. NIPT and New-born screenings help identify rare diseases as early as possible

Non-invasive prenatal testing (NIPT) is a screening method that analyses a small blood sample from the expectant mother to examine the DNA of the unborn child.

This test can detect chromosomal abnormalities such as Down syndrome, trisomy 18, trisomy 13, and chromosome microdeletions or duplications. It can also identify single-gene disorders, including thalassemia, cystic fibrosis, sickle cell anaemia and neurodevelopmental disorders.

In contrast, newborn screening facilitates early diagnosis of various rare diseases through a simple blood test from the baby’s heel or a urine test.

Early detection allows for timely intervention, significantly improving health outcomes and preventing long-term complications. By enabling prompt treatments such as medication, dietary adjustments, or other personalised therapies, early screening ensures a healthier future for the child.

5. Advancements in rare disease diagnosis

Advancements in genomics, such as next-generation sequencing (NGS) and whole-genome sequencing (WGS), are transforming the diagnosis of rare diseases.

These technologies enable faster, more comprehensive, and cost-effective genetic analysis, making testing more accessible to a wider population.

As a result, individuals can receive quicker diagnoses and benefit from better-informed treatment decisions. With ongoing technological progress, we can anticipate even more precise, personalised approaches to diagnosing and managing rare diseases in the future.