Okay, let's tackle this question. The patient is a 30-year-old woman with sudden onset of breathlessness, anxiety, palpitations, and a feeling of impending doom. Physical exam is normal. The question is asking for the diagnosis.

First, the core concept here is panic disorder. Panic attacks typically present with these acute symptoms without underlying physical causes. The key elements are the sudden onset, the specific symptoms like palpitations and anxiety, and a normal physical exam.

Why is panic disorder the correct answer? Well, panic attacks are characterized by these sudden episodes of intense fear with physical symptoms. The DSM-5 criteria include at least four symptoms occurring abruptly, peaking in minutes. The absence of physical findings suggests no organic cause, which is common in panic attacks.

Now, looking at the other options. If the options were conditions like asthma, heart attack, or hypoglycemia, they would have different presentations. For example, asthma would have wheezing or respiratory issues on exam, a heart attack might show ECG changes or elevated enzymes, and hypoglycemia would have low blood sugar. But since the exam is normal, these are less likely. Another possibility is a phobia, but those are usually triggered by specific situations, not sudden onset without context.

The clinical pearl here is to remember that panic attacks can mimic other medical emergencies, so a thorough differential is important. But when the physical exam is normal and symptoms are acute, panic disorder should be high on the list. Also, the "impending doom" is a classic sign.

So the correct answer is panic disorder. The other options can be ruled out based on the normal exam and symptom profile.

**Core Concept**
This question assesses the recognition of **panic disorder** as a cause of acute, unexplained symptoms like breathlessness, palpitations, and anxiety. Key clinical features include sudden onset, absence of physical pathology on examination, and the presence of "impending doom," aligning with DSM-5 criteria for panic attacks.

**Why the Correct Answer is Right**
Panic attacks are characterized by abrupt onset (minutes), peak intensity within 10 minutes, and a cluster of somatic and psychological symptoms (tachycardia, diaphoresis, dyspnea, fear of losing control). The normal physical exam rules out cardiac, pulmonary, or metabolic causes (e.g., myocardial infarction, asthma, hypoglycemia). The "feeling of impending doom" is a hallmark of panic disorder, distinguishing it from other anxiety disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** *Asthma* would present with wheezing or prolonged expiratory phase on exam.
**Option B:** *Myocardial infarction* would show ECG changes or elevated troponins.
**Option C:** *Hypoglycemia* would present with confusion, tremors, and low blood glucose.
**Option D:** *Generalized anxiety disorder* involves chronic, non-sudden anxiety, not acute panic symptoms.

**Clinical Pearl / High-Yield Fact**
Never forget that **panic attacks can mimic life-threatening emergencies**, but a normal physical exam and labs (e.g., ECG, glucose) help confirm the diagnosis. Use the **"5-10-15" rule**: if symptoms resolve within

✓ Correct Answer: A. Panic attack