Musculoskeletal Strain: This is the most common cause of muscular pain in adolescents, often resulting from overuse, poor posture, or trauma. The symptoms can be localized to the neck, chest, and shoulder areas due to strain on the muscles and tendons.

Fibromyalgia: A condition characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory, and mood issues. It can present with pain in the neck, chest, and shoulder regions.
Sports Injuries: Adolescents involved in sports are prone to injuries such as strains, sprains, or overuse injuries that can cause pain in these areas.
Stress and Tension: Psychological stress can manifest as physical tension, leading to pain in the neck, chest, and shoulders.

Cardiac Issues (e.g., Myocarditis, Pericarditis): Although less common, cardiac conditions can present with chest pain and must be considered, especially if accompanied by other symptoms like shortness of breath or palpitations.
Pulmonary Embolism: A rare but potentially life-threatening condition that can cause sudden onset of chest pain, which should be considered, especially in the presence of risk factors.
Spinal Cord Injury or Herniated Disk: Conditions that can cause severe pain and neurological symptoms, requiring immediate medical attention.

Polymyalgia Rheumatica: An inflammatory condition that causes muscle pain and stiffness, primarily in the shoulders and hips, but can also affect the neck and chest.
Dermatomyositis: A rare inflammatory disease characterized by muscle weakness and skin rash, which can cause pain in the muscles of the neck, chest, and shoulders.
Neuromuscular Disorders (e.g., Muscular Dystrophy): A group of diseases that progressively weaken the muscles, which can lead to pain and weakness in the affected areas.