Reactive Lymphadenitis: This is the most common cause of cervical lymphadenopathy, often resulting from a viral upper respiratory tract infection. The lymph nodes are typically tender, mobile, and less than 1 cm in size.

Tuberculosis: A significant cause of cervical lymphadenopathy, especially in endemic areas or in individuals with risk factors such as immunocompromised states. Symptoms can include fever, night sweats, and weight loss.
Streptococcal or Staphylococcal Infections: Bacterial infections can cause lymphadenopathy, often associated with signs of infection like redness, warmth, and swelling in the affected area.
Toxoplasmosis: Especially in immunocompromised patients, toxoplasmosis can cause cervical lymphadenopathy. It's often associated with other systemic symptoms.
Mononucleosis (Infectious Mononucleosis): Caused by Epstein-Barr virus, it can lead to lymphadenopathy, fever, and sore throat.

Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can present with cervical lymphadenopathy. It's crucial to consider this diagnosis, especially in the absence of infectious symptoms or if the lymphadenopathy is persistent or growing.
Metastatic Cancer: Cancers of the head and neck, lung, or breast can metastasize to cervical lymph nodes. A thorough examination and history are essential to identify risk factors or primary tumor sites.
HIV: Human Immunodeficiency Virus infection can cause persistent generalized lymphadenopathy. Identifying HIV is critical due to its significant implications for patient management and prognosis.

Sarcoidosis: A systemic granulomatous disease that can cause lymphadenopathy, among other symptoms like skin lesions, eye involvement, and pulmonary symptoms.
Kikuchi Disease (Histocytic Necrotizing Lymphadenitis): A rare, self-limiting condition that predominantly affects young women, presenting with cervical lymphadenopathy and fever.
Castleman Disease: A rare disorder that can cause lymphadenopathy, often associated with systemic symptoms like fever and weight loss. It can be unicentric (localized) or multicentric (systemic).
Kimura Disease: A chronic inflammatory disorder that can cause lymphadenopathy, typically in the head and neck region, and is often associated with eosinophilia and IgE elevation.