MYOLOGY AND MUSCLES

Muscle and disease

When muscle malfunctions or weakens, the consequences can be severe, and even irreversible.

Neuromuscular diseases

There are around 400 of them, with a wide range of causes, and they can affect the muscle, its innervation or its metabolism. They are many and varied, and can impair movement, breathing and cardiac function, leading to disability of varying severity and, in some cases, proving fatal. Most are genetic, although some are autoimmune or inflammatory.

In France, between 40,000 and 50,000 people are living with a neuromuscular disease.

One example: autoimmune myasthenia gravis

What is autoimmune myasthenia gravis? What are its symptoms? What causes it? Are there any treatments?

The answer, in just one minute, from Rozen Le Panse (team leader of the Myasthenia gravis: aetiology, pathophysiology & therapeutic approach team, Center of Research in Myology)

Find out more about the different neuromuscular diseases

Chronic diseases

In many chronic diseases, such as metabolic and cardiovascular diseases, but also cancer and diabetes, a loss of muscle mass and strength is observed, which affects patients’ quality of life and can be directly linked to increased mortality.

For example:

  • months after a stroke, a loss of muscle mass of nearly 4% is seen in the lower limb and 8% in the upper limb, whatever the severity of the stroke.
  • Cancerous tumours, and the aggressive treatments used to fight them, damage and weaken patients’ muscles, whatever the stage of the disease and their nutritional status. Good muscle health is an extremely important factor in prognosis and treatment response in many cancers.
  • Heart failure causes particularly marked muscle deconditioning.

Sarcopenia

It is inevitable: as we age, our muscles waste away. The cause is the gradual depletion of our reserve of muscle stem cells (MuSCs), which keep our muscle mass constant. From the age of 20, 4% of muscle mass is lost every decade. Beyond a certain threshold, from the age of 50, this phenomenon is called sarcopenia.

Sarcopenia is characterised by a progressive, generalised loss of mass, strength and quality across the whole musculature from the age of 50, which can eventually lead to a reduction of more than 30% in initial muscle mass.

Its consequences are many, and include an increased risk of falls (the leading cause of injury-related death in people over 65), as well as dependency and loss of independence.

Recognised as a disease by the World Health Organization in 2016, sarcopenia is thought to affect nearly one in five people over 60.

France Pietri-Rouxel, leader of the Gene therapy for DMD & pathophysiology group, has identified a protein in humans and shown that its expression correlates with the loss of muscle mass in older adults.