**Core Concept**
Panic disorder is characterized by recurrent unexpected panic attacks, which are discrete periods of intense fear or discomfort, often accompanied by physical symptoms such as palpitations, sweating, and derealization. These episodes are typically short-lived, lasting between 5-30 minutes, and are often followed by persistent fear of experiencing another episode.

**Why the Correct Answer is Right**
The patient's presentation of sudden onset anxiety attacks with associated physical symptoms such as palpitations, sweating, and derealization is consistent with the diagnostic criteria for panic disorder. The duration of these episodes, lasting 20-25 minutes, is also typical of panic attacks. Furthermore, the patient's fear of experiencing another episode is a hallmark of panic disorder, indicating a significant level of distress and impairment in daily functioning. The absence of any underlying medical condition or other psychiatric disorder that could explain the symptoms further supports a diagnosis of panic disorder.

**Why Each Wrong Option is Incorrect**
**Option A:** Generalized anxiety disorder (GAD) is characterized by excessive and persistent worry about everyday things, which is not present in this case. While GAD can co-occur with panic disorder, the patient's symptoms are more consistent with panic attacks.
**Option B:** Obsessive-compulsive disorder (OCD) is characterized by recurrent, intrusive thoughts (obsessions) and repetitive behaviors (compulsions) aimed at reducing anxiety. The patient's symptoms do not include any obsessive or compulsive features.
**Option D:** Tourette's syndrome is a neurodevelopmental disorder characterized by chronic motor and vocal tics. The patient's symptoms are not consistent with Tourette's syndrome.

**Clinical Pearl / High-Yield Fact**
Panic disorder often co-occurs with other anxiety disorders, such as agoraphobia, social anxiety disorder, and specific phobias. It is essential to assess for these comorbidities when diagnosing panic disorder to ensure comprehensive treatment.

✓ Correct Answer: C. Panic disorder.