Musculoskeletal pain: This is often the most common cause of chest pain in teenagers, resulting from strained muscles or inflammation in the chest wall. The pain is typically sharp and localized, worsening with movement or deep breathing.

Asthma or allergic reactions: These conditions can cause chest tightness or pain, especially if the girl has a history of allergies or asthma. Symptoms may include wheezing, coughing, and shortness of breath.
Gastroesophageal reflux disease (GERD): GERD can cause chest pain that is often described as burning and may be accompanied by symptoms like heartburn and difficulty swallowing.
Precordial catch syndrome: This condition causes sharp, stabbing pain in the chest that can be quite frightening but is usually harmless and resolves on its own.

Myocardial infarction (heart attack): Although rare in teenagers, it's crucial not to miss this diagnosis, especially if there's a family history of early heart disease or if the patient has risk factors like obesity or smoking.
Pulmonary embolism: This is a blood clot in the lungs that can be life-threatening. Risk factors include recent surgery, immobilization, or a family history of clotting disorders.
Pneumonia or pneumothorax: Infections or air in the chest cavity can cause severe chest pain and are medical emergencies.

Pericarditis: Inflammation of the sac surrounding the heart, which can cause sharp chest pain that improves with sitting up and leaning forward.
Mitral valve prolapse: A condition where the valve between the heart's chambers doesn't close properly, potentially leading to chest pain, though it's more commonly associated with palpitations and murmurs.
Spontaneous coronary artery dissection (SCAD): A rare cause of heart attack, more common in young women, where there's a tear in the artery wall.