Tuberculosis (TB): Night sweats are a classic symptom of TB, and syncope can occur due to anemia, dehydration, or other complications of TB. The combination of these symptoms, especially in areas with high TB prevalence, makes TB a leading consideration.

Lymphoma: Both night sweats and syncope can be symptoms of lymphoma. Night sweats are part of the "B symptoms" (along with fever and weight loss) that can indicate a more aggressive disease or the need for prompt treatment.
Infective Endocarditis: This condition can cause night sweats due to the infectious process and syncope due to embolic events or heart failure. The combination of these symptoms, especially in intravenous drug users or those with a history of heart disease, should prompt consideration of infective endocarditis.
Anemia: Severe anemia can lead to syncope due to inadequate oxygen delivery to the brain. Night sweats can be associated with chronic diseases that cause anemia, such as chronic kidney disease or malignancies.

Pulmonary Embolism (PE): While PE might not directly cause night sweats, it can cause syncope due to a sudden decrease in cardiac output. If a patient has risk factors for PE (such as recent travel, surgery, or cancer), it's crucial to consider this diagnosis due to its high mortality rate if untreated.
Cardiac Tamponade: This condition can cause syncope due to impaired cardiac filling and subsequent decreased cardiac output. Night sweats could be associated with underlying conditions leading to tamponade, such as malignancy or TB. The high mortality rate of untreated tamponade makes it a "do not miss" diagnosis.
Aortic Dissection: Although night sweats are not a typical symptom, aortic dissection can cause syncope due to severe pain, cardiac tamponade, or disruption of blood flow to the brain. Given its high mortality rate, aortic dissection must be considered in the differential diagnosis of syncope, especially in patients with risk factors such as hypertension or aortic aneurysm.

Pheochromocytoma: This rare tumor can cause episodic hypertension, leading to syncope. Night sweats can occur due to the catecholamine surges associated with the tumor. Although rare, pheochromocytoma is a critical diagnosis to consider due to its potential for severe, life-threatening complications if not treated.
Brugada Syndrome: A genetic disorder that affects the heart's electrical system, potentially leading to syncope and sudden cardiac death. While night sweats are not a direct symptom, the syndrome's severity warrants its inclusion in the differential diagnosis of syncope, especially in young individuals or those with a family history of sudden cardiac death.