Chronic rhinosinusitis is a medical condition caused by inflammation of the nasal cavity and paranasal sinuses. Chronic rhinosinusitis can be caused by anything that leads to chronic inflammation of the nasal cavity and paranasal sinuses including allergies, upper respiratory tract infections, smoking, cystic fibrosis, exposure to irritants, aspirin intolerance, and autoimmune diseases. People with chronic rhinosinusitis are more likely to develop a type of non-cancerous growth in the nasal cavity or paranasal sinuses called a sinonasal inflammatory polyp.
When we breathe, air enters our body through our nose and mouth and travels down a long tube called the trachea into our lungs. The inside of the nose is called the nasal cavity and it helps to warm and clean the air before it reaches our lungs.
The nasal cavity is surrounded by small paired (there is on each side of the face) air-filled spaces called paranasal sinuses that connect to the nasal cavity by small openings. Because the nasal cavity and sinuses are connected to each other, pathologists describe this area of the body as the sinonasal tract. The paranasal sinuses include the maxillary sinus, frontal sinus, ethmoid sinus, and sphenoid sinus.
The inside of the nasal cavity and the paranasal sinuses are lined by specialized epithelial cells that form a barrier called the epithelium. The tissue underneath the epithelium is called stroma and it is made up of blood vessels and small round structures called glands that make a substance called mucin. The epithelium and underlying stroma combine to create a layer of tissue called sinonasal mucosa.
The diagnosis of chronic rhinosinusitis is usually made after a small tissue sample is removed in a procedure called a biopsy. The tissue is then examined under the microscope by a pathologist.
When examined under the microscope, the tissue sample is usually made up of multiple pieces of sinonasal mucosa. Large numbers of specialized inflammatory cells including neutrophils, eosinophils, plasma cells, and lymphocytes are typically seen within the stroma. Pathologists sometimes use the term chronic allergic rhinosinusitis when most of the inflammatory cells within the stroma are eosinophils. The stroma also tends to look white under the microscope because it is full of fluid. This type of change is called edema. Inflammatory cells such as neutrophils and eosinophils may also be seen in the epithelium on the surface of the tissue. When these same features are seen in a growth that sticks out from the surface of the tissue, it is called a sinonasal inflammatory polyp.