Duchenne muscular dystrophy
Signs and symptoms
Boys with DMD look healthy at birth. Some boys can be late walkers. This means they start to walk on their own after the age of 18 months. There may also be delays in other motor milestones and language development.
Symptoms of muscle weakness become more evident around the age of 2-4 years. From this age, boys with DMD may seem clumsy and fall often. They often have a “funny” run where they cannot lift their legs as much as their peers. They may have trouble hopping and climbing stairs. To get up from the floor, they roll on their tummy and walk their hands up their legs to stand, known as Gowers' Manoeuvre. They might show enlarged calf muscles due to abnormal muscle tissue.
By the time they reach school age, boys with DMD are unable to walk as far or as fast as other children. They get tired when walking long distances and may fall down more than their peers. At this age, they may walk on their toes with their feet apart, knees locked and back arched (“waddling gait”). The muscles of the shoulder and upper arm also become weaker. Children can have difficulty raising their arms above their head.
Children with DMD can also present with behavioural problems or learning difficulties. Not all children with DMD will experience these. Learning difficulties can include:
difficulties with language comprehension
learning to read
problems with counting and arithmetic
short term working memory
There is a higher risk of:
Attention Deficit Hyperactivity Disorder
Autistic Spectrum Disorder
Obsessive Compulsive Disorder.
Unlike muscle weakness, learning difficulties in DMD do not get worse overtime. They are more frequent in boys carrying a mutation in the distal part of the dystrophin gene (after exon 44).
The heart and the diaphragm are also muscles and generally start declining from the age of 10 years. Lung function decline leads to a weak cough and necessitates overnight ventilation. This can lead to full-time dependence on a ventilator.
The current standards of care have increased life expectancy by about 10 years or more. Despite this, some boys and young men with DMD still die in their teens.
Children and adults with DMD can develop behavioural problems. This is in reaction to their condition and not being able to do the things they would like to do. They are also aware of their condition getting worse over time. This can lead to tantrums, aggressiveness or depression.