Mononucleosis (Infectious Mononucleosis): This condition, caused by the Epstein-Barr virus, is characterized by swollen lymph nodes, fatigue, and can lead to sleep disturbances due to discomfort or other associated symptoms like fever and sore throat.

Strep Throat: An infection caused by Group A Streptococcus, leading to swollen lymph nodes in the neck, sore throat, and potentially trouble sleeping due to throat pain.
Tuberculosis (TB): Although less common in some regions, TB can cause swollen lymph nodes, especially in the neck, and systemic symptoms like fatigue and sleep disturbances.
Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can present with swollen lymph nodes, and systemic symptoms such as fatigue and sleep disturbances due to the disease itself or associated anxiety and stress.

HIV Infection: Early stages of HIV infection can present with swollen lymph nodes and systemic symptoms including sleep disturbances. Missing this diagnosis could lead to delayed treatment and significant morbidity.
Thyroid Cancer: Although rare, thyroid cancer can cause swollen lymph nodes in the neck and systemic symptoms. Early detection is crucial for effective treatment.
Lymph Node Metastasis from Other Cancers: Metastasis to the lymph nodes from other primary cancers (e.g., breast, lung) is a critical diagnosis not to miss, as it significantly affects treatment and prognosis.

Castleman Disease: A rare disorder that involves an overgrowth of cells in the lymph nodes, which can cause swollen lymph nodes, fever, and other systemic symptoms including sleep disturbances.
Kikuchi-Fujimoto Disease: A rare, self-limiting condition that causes swollen lymph nodes, usually in the neck, fever, and might lead to sleep disturbances due to discomfort or other symptoms.
Sarcoidosis: Although more commonly associated with lung and skin manifestations, sarcoidosis can cause swollen lymph nodes and systemic symptoms, including sleep disturbances due to its effects on various body systems.