Sialadenitis: This is an inflammation of the salivary gland, often caused by bacterial or viral infections. It's the most common cause of salivary gland enlargement and can be acute or chronic.

Sialolithiasis: This condition involves the formation of stones within the salivary glands, which can cause obstruction and subsequent enlargement of the gland.
Benign Salivary Gland Tumors (e.g., Pleomorphic Adenoma): These are common, non-cancerous tumors that can cause enlargement of the salivary gland.
Mumps: A viral infection that can cause parotid gland enlargement, especially in children.

Malignant Salivary Gland Tumors: Although less common than benign tumors, cancers such as mucoepidermoid carcinoma or adenoid cystic carcinoma can cause salivary gland enlargement and have significant implications for treatment and prognosis.
Sjögren's Syndrome: An autoimmune disorder that can cause inflammation and enlargement of the salivary glands, among other symptoms.
HIV-Associated Salivary Gland Disease: Patients with HIV can experience salivary gland enlargement due to various conditions, including lymphoepithelial lesions.

Sarcoidosis: A systemic disease that can cause granulomatous inflammation in various organs, including the salivary glands, leading to their enlargement.
IgG4-Related Disease: A condition characterized by elevated IgG4 levels and can cause inflammation and enlargement of the salivary glands, among other organs.
Granulomatosis with Polyangiitis (formerly known as Wegener's Granulomatosis): A rare autoimmune disorder that can affect various parts of the body, including the salivary glands, causing their enlargement.