Infectious Lymphadenitis: This is often the most common cause of localized lymphadenopathy, resulting from bacterial, viral, or fungal infections. The lymph nodes become swollen in response to an infection in the surrounding area.

Reactive Lymphadenopathy: This occurs in response to a non-infectious, inflammatory process or injury, such as a skin infection, abscess, or even a recent vaccination.
Malignant Lymphoma: Although less common than infectious causes, lymphomas can present with localized lymphadenopathy, especially if the disease is in its early stages.
Metastatic Cancer: Cancer from other parts of the body can spread to the lymph nodes, causing localized lymphadenopathy. The likelihood depends on the primary cancer site and its propensity to metastasize to lymph nodes.

Tuberculosis (TB): TB can cause localized lymphadenopathy, particularly in the cervical or supraclavicular regions. It's crucial to consider TB, especially in individuals from endemic areas or with risk factors for TB exposure.
Cat-Scratch Disease: Caused by Bartonella henselae, this condition typically presents with localized lymphadenopathy near the site of a cat scratch or bite.
Lymphogranuloma Venereum (LGV): A sexually transmitted infection caused by certain strains of Chlamydia trachomatis, LGV can lead to localized lymphadenopathy, often in the inguinal region.

Kikuchi-Fujimoto Disease: A rare, self-limiting condition that primarily affects young women, characterized by localized lymphadenopathy, usually in the cervical region, and is often accompanied by fever and night sweats.
Kimura Disease: A chronic inflammatory disorder that typically presents with localized lymphadenopathy and eosinophilia, more commonly seen in Asian males.
Castleman Disease: A rare disorder that can cause localized lymphadenopathy, characterized by an overgrowth of cells in the lymph node, which can be unicentric (localized) or multicentric (widespread).