## **Core Concept**
The question pertains to the identification of pathognomonic features of maxillary sinusitis, which is an inflammation of the maxillary sinus, one of the paranasal sinuses. Pathognomonic features are signs or symptoms that specifically point to a particular disease. In the context of maxillary sinusitis, these features help in diagnosing the condition accurately.

## **Why the Correct Answer is Right**
The correct answer, ., implies that facial pain, particularly in the cheek area (infraorbital region), and tenderness are pathognomonic features of maxillary sinusitis. This is because the maxillary sinus is located in the maxillary bone, and inflammation of this sinus causes pain and tenderness in the overlying facial structures. The pain may also radiate to the teeth, especially the upper molars, due to the close proximity of the sinus floor to the dental apices.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Although headache can be a symptom of maxillary sinusitis, it is not pathognomonic as it can occur in many other conditions.
- **Option B:** Similarly, nasal discharge can be associated with maxillary sinusitis but is not specific to this condition alone.
- **Option D:** While facial swelling might occur in severe cases of maxillary sinusitis, it is not as specific or commonly recognized as a pathognomonic feature compared to facial pain and tenderness.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that maxillary sinusitis often presents with referred pain to the upper teeth due to the close anatomical relationship between the sinus floor and the dental apices. This can sometimes lead to dental consultations initially. A thorough history and physical examination, including nasal endoscopy and imaging studies like X-rays or CT scans, are crucial for an accurate diagnosis.

## **Correct Answer:** . Facial pain and tenderness.