The different types of muscular dystrophy are distinguished by their symptoms and severity, and by their genetic causes. The primary types are listed here.
Duchenne muscular dystrophy (DMD)
The most common and severe type, DMD, results from lack of dystrophin, a protein required for proper muscle function. Muscle progressively wastes away and is replaced by connective and fatty tissue. Weakness begins in the upper legs and pelvis. People with DMD may also:
• Suffer falls
• Have difficulty rising from lying or sitting
• Waddle when walking
• Have difficulty running and jumping
• Have calf muscles that appear large
DMD appears typically in boys aged three to five and progresses rapidly. Most cannot walk by age 12 and may later need a respirator.
Becker muscular dystrophy
Becker MD is also caused by dystrophin deficiency. Symptoms are similar to DMD, though less severe.
Patients may:
• Suffer falls
• Have difficulty rising from the floor
• Walk on tiptoes
• Have muscle cramping
Becker MD appears primarily in males aged 11-25. Some never need a wheelchair; others become unable to walk in their teens or later.
Myotonic muscular dystrophy
The most common adult form, myotonic MD, affects people aged 20-30. It causes inability to relax muscles following sudden contraction. Other symptoms include:
• Long, thin face and neck
• Swallowing difficulties
• Vision problems, e.g. drooping eyelids, cataracts
• Baldness at front of scalp
• Weight loss
• Increased sweating
• Drowsiness
• Heart problems
• Irregular menstruation
• Infertility/impotence
Limb-girdle muscular dystrophy
Limb-girdle MD usually appears in adolescence or young adulthood. Most patients become severely disabled and can’t walk within 20 years of onset.
Patients may:
• Develop weakness around hips, spreading to shoulders, legs and neck
• Suffer falls
• Have trouble rising from sitting, ascending stairs or carrying items
• Waddle when walking
• Have a rigid spine
Distal muscular dystrophy
Distal MD affects the muscles of the forearms, hands, lower legs and feet. It is caused by defects in the protein dysferlin. Symptoms may include:
• Inability to perform hand movements
• Difficulty extending fingers
• Trouble walking and ascending stairs
• Inability to hop or stand on heels
It typically appears from ages 40-60. It is less severe and progresses more slowly than other forms of MD, but can spread to other muscles. Patients may eventually need a ventilator.
Emery-Dreifuss muscular dystrophy
Emery-Dreifuss MD usually begins in childhood or adolescence, mainly affecting boys.
Weakness begins in the upper arm and lower leg muscles. Patients may also:
• Develop shortening of muscles around joints, preventing free movement
• Have elbows locked in a flexed position
• Develop shoulder deterioration
• Have a rigid spine
• Walk on toes
• Experience mild facial weakness
Heart problems often develop by 30.
Congenital muscular dystrophy
Muscle control problems appear by age two. Patients often need support to sit or stand and may never learn to walk. Some live into adulthood with only mild disability.
Patients may have:
• Shortening of muscles or tendons around joints, preventing free movement
• Scoliosis (curvature of the spine)
• Trouble breathing and swallowing
• Foot deformities
• Intellectual disabilities
Facioscapulohumeral muscular dystrophy (FSHD)
FSHD refers to the areas affected: face (facio), shoulders (scapulo) and upper arms (humeral).
Lack of facial mobility is an early warning sign: difficulty opening and closing the eyes, and inability to smile or pucker the mouth. Other possible symptoms include:
• Muscle wasting that makes shoulders appear slanted and shoulder blades protrude
• Impaired reflexes in the biceps and triceps
• Trouble swallowing, chewing or speaking
• Hearing problems
• Spine with swayback curve
FSHD typically affects adolescents but may occur up to 40. Life span is usually normal; symptoms vary from mild to severely disabling.
Oculopharyngeal muscular dystrophy (OPMD)
OPMD affects muscles around the eyes, and sometimes other muscles. Symptoms usually develop in late middle age, including:
• Vision problems, e.g. drooping eyelids
• Difficulty swallowing
• Muscle wasting and weakness in neck, shoulders and sometimes limbs
• Heart problems
References:
Muscular Dystrophy Association website. www.muscular-dystrophy.org
National Institute of Neurological Disorders and Stroke (NINDS). (2011). Muscular dystrophy: Hope through research.
