As the disease continues to progress through the adolescent years, weakness in the muscles typically accelerates and other signs and symptoms may become apparent:

• Overwhelming fatigue
• Respiratory compromise or muscle weakness leading to respiratory infections
• Grooved tongue (with deep fissures, cracks, and grooves)
• Gradual decline in muscle effectiveness (muscle atrophy)
• Arm and leg weakness
• Joint instability
• Joint dislocation
• Numbness and tingling or pain in hands and feet
• Diminished or lack of deep tendon reflexesA tendon is a tough cord or band of dense white fibrosis connective tissue that unites a muscle with another part (for example a bone) and exerts a reflex action in which a muscle is made to contract by a blow upon its tendon. (areflexia)
• Inability to sense the orientation of body parts and balance issues (proprioception)
• Difficulties with balance and proprioception (inability to sense)
• Decreased response to touch below the knee
• High arches and drop foot (difficulty lifting the front part of the foot) or flat feet