Viral infections (e.g., mumps): This is a common cause of salivary gland enlargement in children, particularly in those who have not been vaccinated against mumps. The parotid gland is most commonly affected, and the condition is usually self-limiting.

Recurrent parotitis: This condition involves recurrent episodes of parotid gland inflammation, often due to a bacterial or viral infection. It's more common in children and can cause intermittent salivary gland enlargement.
Sialadenitis: This is an infection of the salivary gland, which can be caused by bacteria or viruses. It can lead to swelling and pain in the affected gland.
Salivary gland stones (sialolithiasis): Although less common in young children, stones in the salivary glands can cause obstruction and subsequent enlargement of the gland.

HIV infection: Salivary gland enlargement can be a manifestation of HIV infection in children, often associated with other systemic symptoms.
Sjögren's syndrome: Although rare in children, this autoimmune disorder can cause salivary and lacrimal gland enlargement, among other symptoms.
Lymphoma: Although uncommon, lymphoma can present with salivary gland enlargement due to lymph node involvement within the gland.

Salivary gland tumors: Both benign (e.g., pleomorphic adenoma) and malignant tumors can cause salivary gland enlargement, but they are rare in young children.
Cystic fibrosis: This genetic disorder can lead to salivary gland dysfunction and enlargement, though it's more commonly associated with respiratory and gastrointestinal symptoms.
Autoimmune disorders (e.g., IgG4-related disease): These conditions can cause salivary gland inflammation and enlargement, but they are rare and often present with other systemic manifestations.