What condition is characterized by sharp, knifelike pain that worsens with breathing?

Pericarditis is characterized by sharp, knifelike pain that often worsens with breathing and is typically exacerbated by deep breaths or coughing. This intense pain is due to inflammation of the pericardium, the fibrous sac surrounding the heart. The pain may also be relieved by sitting up and leaning forward, which is a common behavioral response in patients experiencing this condition. The sharpness of the pain is distinctive compared to other possible causes of chest pain, and its relation to breathing makes pericarditis particularly identifiable when diagnosing patients.

In contrast, pneumonia generally presents with pain that can be pleuritic (related to the lung's pleura), but the underlying mechanism and nature of the pain might differ from the sharp, positional variation seen in pericarditis. Angina pectoris usually manifests as a pressure-like or squeezing sensation rather than a sharp pain; it typically occurs in response to exertion or emotional stress. Funnel chest, or pectus excavatum, is a structural anomaly that does not typically present with acute pain, especially not of the sharp, knifelike quality mentioned in the question.