Mastering differential diagnosis is a cornerstone of excelling on the USMLE. It's the process of systematically identifying and ranking potential diseases or conditions that could explain a patient's signs and symptoms. This skill is crucial for accurate patient management and forms the basis of clinical reasoning.

A robust differential diagnosis begins with a thorough understanding of the patient's presentation. This includes their chief complaint, history of present illness, past medical history, family history, social history, and a comprehensive review of systems. Physical examination findings are equally vital in narrowing down possibilities.

Several mnemonic devices and frameworks can aid in generating comprehensive differentials, especially for common presentations. These help ensure you don't overlook critical diagnoses.

While frameworks are helpful, true mastery comes from developing strong clinical reasoning skills and pattern recognition. This involves connecting constellations of symptoms, signs, and lab findings to specific disease entities. The more cases you review and the more you practice, the better you become at identifying these patterns.

Common mistakes include premature closure (settling on a diagnosis too early), anchoring bias (over-reliance on initial information), and failing to consider rare but critical diagnoses. To avoid these:

• Always maintain a broad differential, especially in the initial stages.
• Actively seek disconfirming evidence for your leading diagnoses.
• Review your differentials with a critical eye, asking 'What else could this be?'
• Stay updated on common and emerging disease patterns.

The best way to hone your differential diagnosis skills is through consistent practice. Utilize question banks, case studies, and clinical vignettes. For each case, pause before looking at the answer and generate your own differential, then compare it to the provided solution and explanations. Understanding why certain diagnoses are more likely than others is key.