Differential Diagnosis for an 18-Year-Old Female with Fever and Chest Pain Radiating to the Left Arm

Single Most Likely Diagnosis

• Viral Pericarditis: This condition is characterized by inflammation of the pericardium, often due to viral infections. The symptoms of fever, chest pain (typically sharp and improving with sitting up and leaning forward), and radiation to the left arm are consistent with pericarditis. The age and acute onset also support this diagnosis.

Other Likely Diagnoses

• Pneumonia: Given the fever and chest pain, pneumonia is a plausible diagnosis. The pain could be pleuritic, especially if it worsens with deep breathing or coughing, which could radiate to the left arm if the left lower lobe is involved.
• Costochondritis: Inflammation of the cartilage that connects the ribs to the sternum can cause sharp pains in the chest that may radiate to the arm, especially with movement or deep breathing.
• Gastroesophageal Reflux Disease (GERD): GERD can cause chest pain that may radiate to the arm, often accompanied by a burning sensation in the chest and throat, especially after eating.

Do Not Miss Diagnoses

• Myocardial Infarction (MI): Although less common in young females, MI can occur, especially with risk factors such as hypercoagulable states or drug use. The presentation can be atypical, making it crucial not to miss.
• Pulmonary Embolism (PE): Sudden onset of chest pain and fever could be indicative of a PE, especially if there's a history of recent immobilization, surgery, or family history of clotting disorders.
• Aortic Dissection: A life-threatening condition where there is a tear in the aorta's inner layer. The pain is often severe, tearing, and radiates to the back or arm.

Rare Diagnoses

• Pneumothorax: Air in the pleural space can cause sudden chest pain and shortness of breath, which might radiate to the arm if the pneumothorax is large enough to irritate the nerves.
• Esophageal Rupture: A severe condition that can cause chest pain radiating to the back or arm, often accompanied by difficulty swallowing and severe retching.
• Thoracic Outlet Syndrome: Compression of the nerves or blood vessels between the collarbone and first rib can cause pain in the chest and arm, but it's less likely to be associated with fever.