Hypertensive Crisis: This is the most likely diagnosis given the patient's significantly elevated blood pressure (170/100 mmHg) and symptoms such as a "buzzy" sensation, feeling of increased pressure, and swelling of the hands. The rapid onset and the presence of end-organ damage indicators (e.g., the swelling could indicate fluid retention) support this diagnosis.

Pheochromocytoma: Although less common, this condition involves tumors of the adrenal gland that can cause episodic hypertension, palpitations, sweating, and headache. The patient's symptoms of rapid pulse and severe hypertension could align with this diagnosis, especially if the episodes are episodic.
Primary Aldosteronism: This condition, characterized by excessive production of aldosterone, can lead to hypertension and sometimes edema due to fluid retention. The patient's swelling and hypertension could be indicative of this condition, though it's less likely to present acutely.
Renal Artery Stenosis: This condition involves narrowing of the arteries that supply blood to the kidneys, which can cause severe hypertension. While it's a possible cause of the patient's symptoms, it's less likely to present with such acute onset without other symptoms.

Aortic Dissection: Although the patient denies chest pain, aortic dissection is a life-threatening condition that can sometimes present atypically, especially in younger patients. The absence of classic symptoms does not rule out this diagnosis, and any severe hypertension warrants consideration of aortic dissection.
Pulmonary Embolism: While the patient denies shortness of breath, pulmonary embolism can sometimes present with hypertension and tachycardia. Given the potential for atypical presentations, especially in younger patients, this diagnosis should be considered.
Catecholamine Crisis due to Other Causes (e.g., Cocaine Use, Thyrotoxicosis): These conditions can cause severe hypertension and tachycardia. A thorough history, including substance use and evaluation for thyroid disease, is crucial.

Adrenal Crisis: This condition involves acute adrenal insufficiency, which can sometimes present with hypertension due to fluid retention and mineralocorticoid imbalance. However, it's typically associated with more systemic symptoms such as severe fatigue, abdominal pain, and hypotension, making it less likely in this scenario.
Hyperthyroid Crisis: Although more commonly associated with hypotension, in rare cases, hyperthyroid crisis can present with hypertension. The patient's symptoms of rapid pulse and feeling "off" could be consistent with this diagnosis, but other signs such as exophthalmos, weight loss, and heat intolerance would be expected.