Pulmonary Embolism (PE): Although the patient is young and healthy, PE can occur in anyone, especially if there are underlying risk factors not mentioned (e.g., recent travel, family history of clotting disorders). Pleuritic chest pain, which worsens with deep breathing and can radiate to the back, is a classic symptom. However, the relatively low pulse rate and high saturation might slightly lower the suspicion, but it's still a critical diagnosis to consider due to its potential lethality.

Pneumonia: Could present with pleuritic chest pain, especially if the pneumonia involves the pleura. However, one might expect additional symptoms like fever, cough, or sputum production, which are not mentioned.
Pleurisy: Inflammation of the pleura can cause sharp, stabbing chest pain that worsens with breathing. It can be idiopathic or associated with viral infections, and the presentation could fit, although the lack of other symptoms (like fever or cough) makes it less clear.
Musculoskeletal Pain: Costochondritis or musculoskeletal strain could cause chest pain that might be perceived as pleuritic, especially if it involves the areas where the ribs meet the vertebrae in the back.

Aortic Dissection: Although less common in a young, healthy individual without known risk factors like hypertension, it's a diagnosis that could be catastrophic if missed. The pain is often described as tearing and can radiate to the back, but it typically does not have a pleuritic characteristic.
Pulmonary Hypertension: Could lead to chest pain, but it's usually more chronic and associated with other symptoms like exertional dyspnea.
Cardiac Ischemia/Myocardial Infarction: Less likely in a young, healthy male without risk factors, but it's a critical diagnosis not to miss. The pain of myocardial infarction can sometimes be pleuritic, especially if there is associated pericarditis.

Pneumothorax: Could cause pleuritic chest pain, but one might expect more significant distress and lower oxygen saturation levels, especially if the pneumothorax is large.
Lung Cancer: Extremely rare in a healthy 35-year-old male without risk factors, but could cause pleuritic pain if the tumor involves the pleura.
Empyema or Complicated Parapneumonic Effusion: These conditions involve fluid accumulation in the pleural space, often as a complication of pneumonia, and can cause pleuritic chest pain. However, additional symptoms like fever, weight loss, or productive cough would typically be present.