Infectious Mononucleosis (Mono): Caused by Epstein-Barr virus (EBV), it often presents with fever, sore throat, facial rash (especially after amoxicillin use), and lymphadenopathy, including bilateral lymph node enlargement. The combination of these symptoms makes it a leading consideration.

Lupus: Systemic lupus erythematosus (SLE) can present with a malar rash (butterfly-shaped rash on the face), fever, and lymphadenopathy. Although it's more common in women, the presence of a facial rash and systemic symptoms like fever makes it a plausible diagnosis.
Toxoplasmosis: Especially in immunocompromised patients, toxoplasmosis can cause lymphadenopathy and fever. While a rash is less common, it can occur, making toxoplasmosis a consideration, particularly if there's exposure history.
Cat-Scratch Disease: Caused by Bartonella henselae, it typically presents with lymphadenopathy near the site of the cat scratch, but can occasionally cause more generalized symptoms including fever and rash.

Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can present with lymphadenopathy, fever, and sometimes rash. Given the potential severity of lymphoma, it's crucial not to miss this diagnosis, even though it might be less common than infectious causes.
HIV Infection: Acute HIV infection can present with a variety of symptoms, including fever, rash, and lymphadenopathy. The potential for severe immunocompromise and the importance of early diagnosis make HIV a critical "do not miss" diagnosis.
Tuberculosis (TB): Although less common in some regions, TB can cause fever, lymphadenopathy, and occasionally a rash. Given its potential severity and the importance of public health implications, TB should not be overlooked.

Kawasaki Disease: An acute febrile illness of childhood characterized by inflammation in the walls of medium-sized arteries throughout the body, which can lead to lymphadenopathy, rash, and fever. It's rare but important to consider due to the risk of coronary artery aneurysms.
Juvenile Idiopathic Arthritis (JIA): Can present with fever, rash, and lymphadenopathy, particularly the systemic form of JIA. It's a diagnosis of exclusion but should be considered in the appropriate clinical context.
Sarcoidosis: A systemic granulomatous disease that can cause lymphadenopathy, fever, and occasionally skin rashes. It's less common but should be considered, especially in patients with respiratory or ocular symptoms.