Symptoms of DMD typically begin in early childhood, often between ages 2 and 5, and progress over time. The onset and progression can vary slightly but follow a general pattern:
Early Symptoms (Childhood – 2 to 5 years):
- Developmental Delays: May walk later than average, have difficulty with gross motor skills like running, jumping, and climbing stairs.
- Frequent Falls: Due to muscle weakness, especially in the hips and legs.
- Waddling Gait: An unsteady or waddling walk due to weakness in hip abductor muscles.
- Toe Walking: Walking on the toes or balls of the feet.
- Gowers’ Maneuver: A characteristic way of getting up from the floor, where the child “walks” their hands up their legs to push themselves to a standing position, indicating weakness in the hip and thigh muscles.
- Pseudohypertrophy of Calves: Calf muscles may appear unusually large, but this is due to the replacement of muscle tissue with fat and connective tissue, not true muscle hypertrophy.
- Difficulty with Activities: Trouble keeping up with peers in physical activities.
- Speech Delay: Some children may experience delays in speech development.
- Learning and Behavioral Difficulties: A percentage of individuals with DMD may have some degree of cognitive or behavioral challenges.
Later Symptoms (Late Childhood to Adolescence):
- Progressive Weakness: Muscle weakness spreads from the legs and pelvis to the arms, trunk, and neck.
- Loss of Ambulation: Most individuals with DMD require a wheelchair for mobility by their early teens (around 10-12 years of age).
- Contractures: Shortening of muscles and tendons, leading to fixed deformities at joints, particularly in the ankles, knees, hips, and elbows. This restricts range of motion.
- Scoliosis: Progressive curvature of the spine due to muscle weakness and imbalance.
- Respiratory Weakness: Weakness of the diaphragm and other respiratory muscles leads to shallow breathing, frequent respiratory infections, and eventually respiratory insufficiency.
- Cardiomyopathy: Weakening of the heart muscle, which can lead to heart failure and arrhythmias. This is a major cause of mortality in DMD.
- Feeding Difficulties: As muscles weaken, swallowing can become difficult.
Adult Phase:
Further decline in muscle function, requiring full-time assistance for most activities of daily living.
- Increasing dependence on respiratory support (e.g., non-invasive ventilation).
- Ongoing management of cardiac complications.
