**Core Concept**
Trichotillomania is a psychiatric disorder characterized by a long-term, repetitive, and compulsive behavior of pulling out one's own hair, resulting in noticeable hair loss. This behavior is often a coping mechanism for stress, anxiety, or other emotional distress.

**Why the Correct Answer is Right**
The correct answer, "Associated with patchy hair loss," accurately describes a key feature of trichotillomania. Individuals with trichotillomania typically exhibit patchy areas of hair loss due to the consistent pulling of hair from specific regions of the scalp or body. This behavior can lead to noticeable hair thinning or bald patches, often in a non-uniform pattern. The hair loss is usually accompanied by a strong sense of guilt, shame, or anxiety related to the behavior.

**Why Each Wrong Option is Incorrect**
**Option A:** Irresistible desire to set fire is a characteristic of pyromania, a different psychiatric disorder. While individuals with pyromania may exhibit a strong desire to set fires, this behavior is distinct from the hair-pulling behavior associated with trichotillomania.

**Option B:** Irresistible desire to steal things is a feature of kleptomania, another distinct psychiatric disorder. Kleptomania involves a compulsive urge to steal items, often without any apparent need or benefit, which is not related to the hair-pulling behavior of trichotillomania.

**Option D:** Pathological gambling is a separate psychiatric disorder characterized by compulsive and excessive gambling behavior, often leading to significant personal and financial problems. This behavior is unrelated to the hair-pulling behavior of trichotillomania.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of trichotillomania is the presence of "excoriation" or skin damage resulting from the hair-pulling behavior, which can lead to secondary infections or scarring.

**✓ Correct Answer: C. Associated with patchy hair loss**