Symptoms:

Females rarely develop symptoms. Males will develop symptoms if they inherit the defective gene. Symptoms usually appear in boys at about age 12, but may begin later.

Muscle weakness of the lower body, including the legs and pelvis area, slowly gets worse, causing:

• Difficulty walking that gets worse over time; by age 25-30 the person is usually unable to walk
• Frequent falls
• Difficulty with running, hopping, and jumping
• Loss of muscle mass

Muscle weakness in the arms, neck, and other areas is not as severe as in the lower body.

Other symptoms may include:

• Breathing problems
• Cognitive problems (these do not get worse over time)
• Fatigue
• Loss of balance and coordination

Signs and tests:

The health care provider will do a nervous system (neurological) and muscle examination. A careful medical history is also important, because the pattern of symptom development resembles that of Duchenne's muscular dystrophy. However, Becker muscular dystrophy gets worse much more slowly.

An exam may find:

• Abnormally developed bones, leading to deformities of the chest and back (scoliosis)
• Abnormality of heart muscle function (cardiomyopathy)
• Congestive heart failure or irregular heartbeat (arrhythmias) - rare
• Muscle deformities, including:
  • Contractures of heels and legs
  • Abnormal fat and connective tissue in calf muscles
• Muscle loss that begins in the legs and pelvis, then moves on to the muscles of the shoulders, neck, arms, and respiratory system

Tests that may be done include:

• CPK blood test
• Electromyography (EMG) nerve testing
• Muscle biopsy or genetic blood test