Chronic Rhinosinusitis: This is the most common condition affecting the sinuses and nasal cavity, characterized by inflammation of the mucosal lining. It often involves the maxillary and ethmoid sinuses but can also affect the sphenoid sinus and nasal cavity, making it a likely diagnosis given the involvement of the left maxillary, sphenoid sinuses, and nasal cavity.

Allergic Rhinitis: This condition can cause chronic inflammation in the nasal cavity and sinuses, leading to symptoms similar to those described. It's a common condition that could explain the inflammatory mucosal disease, especially if the patient has a history of allergies.
Acute Bacterial Rhinosinusitis: Although typically presenting with more acute symptoms, an acute bacterial infection could cause significant inflammation in the sinuses and nasal cavity. The involvement of the maxillary and sphenoid sinuses could suggest a bacterial etiology, especially if there's a history of recent upper respiratory infection.
Fungal Sinusitis: This could be a consideration, especially in immunocompromised patients or those with a history of fungal exposure. Fungal sinusitis can cause chronic inflammation and might involve multiple sinuses, including the sphenoid.

Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A systemic vasculitis that can present with sinusitis and nasal cavity inflammation. It's crucial to consider this diagnosis due to its potential for severe systemic complications and the need for early treatment.
Sarcoidosis: This systemic disease can cause granulomatous inflammation in the sinuses and nasal cavity. While less common, missing this diagnosis could lead to delayed treatment of a potentially serious condition.
Invasive Fungal Sinusitis: Especially in immunocompromised patients, this condition can be life-threatening and requires prompt diagnosis and treatment.

Churg-Strauss Syndrome (Eosinophilic Granulomatosis with Polyangiitis): A rare autoimmune condition that can cause sinusitis and nasal inflammation, among other systemic symptoms. It's essential to consider this in patients with asthma and eosinophilia.
Relapsing Polychondritis: A rare disease that can cause inflammation of cartilaginous structures, including those in the nose and sinuses. It might present with chronic sinusitis and nasal symptoms.
Sinusitis due to Parasitic Infections: Rare in many parts of the world but could be considered in travelers or individuals from endemic areas, where parasites might cause sinus and nasal inflammation.