Sialadenitis: This is an inflammation of the salivary gland, which can be caused by bacterial or viral infections. It is the most common cause of submandibular gland swelling due to its susceptibility to obstruction by stones or other debris, leading to infection.

Sialolithiasis: Stones in the submandibular gland or its duct can cause obstruction, leading to swelling and potentially infection. This condition is common due to the gland's anatomy, which makes it prone to stone formation.
Benign tumors (e.g., Pleomorphic Adenoma): Although more commonly associated with the parotid gland, pleomorphic adenomas can occur in the submandibular gland, causing swelling.
Submandibular gland cysts: These can be congenital or acquired and may present as a swelling in the submandibular region.

Malignant tumors (e.g., Adenoid Cystic Carcinoma, Mucoepidermoid Carcinoma): Although less common than benign conditions, malignant tumors of the submandibular gland can present with swelling and must be considered to ensure timely diagnosis and treatment.
Lymphadenopathy: Enlargement of lymph nodes in the submandibular region can mimic gland swelling and may be due to infection, autoimmune diseases, or malignancy.
Granulomatous diseases (e.g., Sarcoidosis, Tuberculosis): These conditions can affect the salivary glands, including the submandibular gland, and must be considered, especially in patients with systemic symptoms or known granulomatous disease.

Sjögren's syndrome: An autoimmune disorder that can affect the salivary glands, leading to swelling among other symptoms.
IgG4-related disease: A condition characterized by inflammation and fibrosis in various organs, including the salivary glands, which can cause swelling.
Kimura disease: A rare, chronic inflammatory disorder that can involve the salivary glands and lymph nodes, leading to swelling in the submandibular region.