Duchenne muscular dystrophy

Biology

Duchenne muscular dystrophy

Eléonore Vallier Isaure Ecomard

Introduction

Historical aspect

Genetic explanations

summary

Consequences

Research/treatment

QUIZZ

introduction

Duchenne dystrophy is :

• a rare genetic muscular dystrophy

• characterized by atrophy (=decrease in the volume of an organ or tissue)

• and degeneration of skeletal, smooth, and cardiac muscles,

• which occurs gradually from childhood onwards.

This disease is also called DMD or Duchenne myopathy.

Next

Beware of the trap! Double-click on the circles to access the text.

History

Numerous research conducted over time on Duchenne muscular dystrophy has led to a gradual understanding of the condition. Today, it is fairly well known.

Timeline

1986-1987

1852

1950-1960

1990-2002

1861

continue

Click on the white part of the speech bubble to view the information

Genetic explanation

Step 0

Step 2

Step 3

Step 1

As usual

Muscle degeneration

Absence of dystrophin

Mutation

Next

Genetics

• Onset: symptoms appear at 3–5 years
• Childhood: loss of walking around 10–12 years, increasing muscle weakness
• Adulthood: severe disability, respiratory and heart complications
• Life expectancy: previously 15–20 years → now 30–40+ years
• The disease gradually worsens over decades.

• Mostly boys (because the disease is X-linked)
• Girls are usually carriers but rarely affected

• Age of onset:

-Symptoms appear around 3–5 years old -The disease worsens during childhood and adolescence

• Are they all over the world?

-Yes, it affects people worldwide -All ethnic groups are concerned

• Are they numerous?

-Rare disease: about 1 in 3,500–5,000 boys -Thousands of patients worldwide

Who are the patients ?

Title

Use this side to give more information about a topic.

Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.

Subtitle

How long does the disease last?

Title

Write a brief description here

COnsequences

Next

COnsequences

• Early stage:

-difficulty running, climbing stairs, frequent falls

• Later:

-loss of walking ability (often around 10–12 years old) -need for a wheelchair

• Daily care includes:

-medical follow-up (heart, lungs) -physiotherapy -assistance for daily activities

• Increasing loss of independence over time

• Progressive muscle weakness → Legs are affected first, then arms and trunk, leading to increasing difficulty with walking and daily movements.
• Loss of mobility → Wheelchair use often becomes necessary in adolescence; dependence for daily activities such as dressing, bathing, and eating.

• Respiratory issues → Weakening of breathing muscles increases the risk of lung infections and may require respiratory support.

• Heart problems → Cardiomyopathy can develop, raising the risk of heart failure.

• Skeletal problems → Scoliosis, joint stiffness, and contractures limit mobility further and can cause pain.

Use this side of the card to provide more information about a topic. Focus on one concept. Make learning and communication more efficient.

Overall consequences

Title

Use this side to give more information about a topic.

How is their daily life?

Title

Subtitle

Write a brief description here

Next

Treatments

1. Current Treatments

2. Ongoing research

Next

Quizz

Next

Next

Next

Next

Thank you for your attention !

Understanding the Genetic Nature of the Disease

It becomes understood that the disease is:

• hereditary

• linked to the X chromosome

This explains why:

• it almost exclusively affects boys

• women are often carriers without being affected

Ongoing research

Mutation of the DMD gene

Location: X chromosomePrecise issue: Mutation in the DMD gene → Often a deletion (most common), but can also be duplication or point mutation

• What happens to the gene?

-The mutation disrupts the genetic instructions: -The reading frame is often shifted -The code becomes incorrect -The protein cannot be properly produced

• Consequence:

No dystrophin is made, or it is incomplete and non-functional

Curent treatments

Muscle degeneration

• What happens over time?

Muscle fibers are repeatedly damaged

• Repair is ineffective:

-Muscle cannot regenerate properly -Damage accumulates

• Long-term consequences:

Muscle tissue is replaced by: -fat -fibrotic (scar) tissue

• Result:

-Progressive muscle weakness -Loss of mobility -Later: respiratory and cardiac complications

As usual: a protein called dystrophin

Location: X chromosomePrecise position: DMD gene →It is one of the largest genes in the human body

What does dystrophin normally do?Dystrophin is an essential protein that:

• Stabilizes the muscle cell membrane
• Protects muscle fibers during contraction
• Connects the internal muscle structure (cytoskeleton) to the surrounding support tissue

Care and treatments

• Introduction of corticosteroids:

-slow down loss of strength -prolong walking ability -improve life expectancy

• Improved medical care:

-respiratory -cardiac -orthopedic

Edward Meryon (United Kingdom)

• First clear clinical description
• Understands that:

-the disease is hereditary -it mainly affects boys

• Also analyzes muscles after death

Major breakthrough

• Discovery of the DMD gene on the X chromosome
• Identification of the missing protein: dystrophin
• The mechanism is finally understood:

-without dystrophin, muscle fibers are fragile -they break during effort -and do not repair properly → muscle degeneration

Guillaume-Benjamin Duchenne de Boulogne (France)

Provides the most complete description

• Links symptoms, progression, and muscle involvement

• His work becomes the medical reference

• The disease is named after him

Absence of dystrophin

• What changes in muscle cells?

Dystrophin is missing

• What does this cause?

-The muscle cell membrane becomes fragile -It is easily damaged during contractions

• Cellular effects:

-Small tears appear in the membrane -Calcium enters abnormally into the cell -This activates damaging processes inside the cell