Myotonic Dystrophy Type 1 (DM1)

Myotonic Dystrophy Type 1 (DM1), also known as Steinert’s disease, is a hereditary muscle disorder. Approximately 1 in 8,000 people are affected by this condition. The severity of the disease varies widely and is classified into four forms: classical, mild, juvenile, and congenital (inborn).

Forms of DM1

Classical or Adult-Onset Form

The classical form is the most common. Symptoms usually appear between the ages of 10 and 50. Key features include:

• Delayed muscle relaxation (myotonia)
• Progressive muscle weakness starting in the face, jaw, and neck muscles, eventually affecting the arms and legs
• Fatigue is a frequent complaint

Other organs can also be affected, including the heart, lungs, brain, eyes, and gastrointestinal system. Weak facial muscles, loss of initiative, and fatigue often lead to communication difficulties. Life expectancy is typically reduced, with most deaths resulting from heart or lung complications. Regular cardiologist monitoring is essential.

Mild or Late-Onset Form

Symptoms of the mild form begin after age 50 and typically include:

• Cataracts as the primary symptom
• Fatigue and mild muscle weakness in some cases

Life expectancy is generally unaffected.

Juvenile form

Symptoms of the juvenile form appear between early childhood and puberty. Initial signs often include:

• Learning difficulties
• Slurred or unclear speech
• Motor clumsiness

As children start school, additional issues such as concentration problems, increased sleep needs, and behavioral problems may become evident. Gastrointestinal problems are also common. Over time, symptoms resembling those of the classical form develop.

Congenital form

The congenital form is the most severe and occurs almost exclusively when the mother transmits the disease to her child. Symptoms in newborns include:

• Severe muscle weakness at birth
• Feeding and swallowing difficulties due to weak mouth and esophagus muscles
• Delayed mental and motor development

Diagnosis

The diagnosis of DM1 is typically made by a neurologist based on characteristic symptoms such as myotonia and muscle weakness. The most precise method is DNA testing, which can be performed using a blood sample.

Key Considerations

• Early Recognition: Early diagnosis helps manage complications, especially cardiac and respiratory issues.
• Regular Monitoring: Cardiologist evaluations are vital to prevent and address heart-related complications.
• Support for Juvenile and Congenital Forms: Multidisciplinary care is crucial for managing developmental delays and motor skill challenges.