Myotonic dystrophy

The most severe form of DM1 is the congenital type, which can affect babies even before birth.

 Symptoms are always noticeable at birth, although they can be more or less severe. Babies with Congenital myotonic dystrophy present at birth with:

• Low muscle tone (described as “floppy babies”)
• Reduced mobility in the arms and legs
• Breathing problems
• Feeding difficulties due to facial weakness and weak sucking
• Facial weakness (open mouth and reduced facial expressions)
• Club foot  (talipes) can be present
• Gastrointestinal problems   

 Babies with Congenital myotonic dystrophy can be very ill. They may need respiratory support and feeding support through a feeding tube. There is a high risk of mortality during the first year of life, usually due to respiratory complications. 

 Children who overcome their initial breathing and feeding problems usually make progress. They go on to achieve all motor milestones (they learn to sit and to walk); however, they are often delayed when compared to peers. They can present with learning difficulties, which can be severe. They will also develop other myotonic symptoms:

• Skeletal muscles:
  • Low muscle tone improves over time.
  • Often have a delay in their motor development compared to healthy children.
  • Children will usually reach motor milestones (being able walk). 
• Facial weakness with open mouth and poor facial expression. As they keep their mouth open, drooling might be an issue, especially in young children.
• Usually described as “clumsy”:
  • They may have frequent falls.
  • Show muscle weakness, causing difficulties in running or climbing stairs.
  • Muscle weakness and wasting progress over time.
  • Clubfeet often improve with time and physiotherapy input.
  • Some children might need special shoes or walking aids.
  • Children with congenital myotonic dystrophy may need to use a wheelchair; they can become tired very suddenly and difficult to manage.  
• Respiratory (breathing) complications are common (in at least 50% of children with congenital myotonic dystrophy) and continue throughout their life. Affected children have a higher risk of respiratory complications during chest infections. In severe cases, children may need ventilator support.
• Feeding problems often resolve with age, although failure to thrive is common.
• Children are often late in achieving bladder and bowel control. This usually improves with time, but bowel problems (constipation and diarrhoea) can persist.
• Cognitive involvement is often the main feature in older children. It can manifest in different ways but cognitive involvement can be severe. It includes:
  • Learning difficulties  
  • Attention Deficit Hyperactivity Disorder
  • Autism Spectrum Disorder
  • Anxiety disorders
  • Behavioural problems
  • Depression

Speech involvement is common and can present with delayed speech and speech problems. They can have particular difficulty with clear pronunciation.

Congenital myotonic dystrophy usually occurs when the mother has DM1. She might not be aware of this and then passes it on to her child in a more severe form. The child's father can also pass on the disease but is very rare for a child to have the congenital form when they inherit the condition from their father.