acute unilateral parotitis is usually due to an obstruction stone or acute bacterial parotitis
acute bilateral parotitis is usually due to mumps
alcoholism, sarcoidosis or HIV may cause chronic bilateral parotidomegaly
tumour including lymphoma may cause parotid enlargement +/- facial nerve palsy
60% of all parotid neoplasms are accounted for by the pleomorphic adenoma, while 8% are mucoepidermoid carcinoma, 7% are Warthin's tumour,
recurrent parotitis of childhood is an uncommon syndrome
autoimmune causes are uncommon and usually are bilateral, and mainly affects women
rarely, a range of other conditions may involve the parotid glands