A 30 year old man since 2 months suspects that his wife is having an affair with his boss. He thinks his friend is also involved from abroad and is providing technological suppo. He thinks people talk negatively about him. His friends tried to convince him but he is not convinced at all. Otherwise he is normal, doesn’t have any thought disorder or other inappropriate behavior. The most likely diagnosis is which of the following?

**Core Concept**
Delusional disorder is a psychiatric condition characterized by the presence of one or more non-bizarre delusions that last for at least a month. These delusions are not explained by a substance or medical condition and are not a symptom of schizophrenia.

**Why the Correct Answer is Right**
The patient's preoccupation with his wife's alleged infidelity, his boss's involvement, and his friend's technological support, despite being convinced by friends otherwise, suggests the presence of a non-bizarre delusion. This is a classic symptom of delusional disorder, where the individual holds a fixed, false belief that is not shared by others. The lack of thought disorder, inappropriate behavior, or other symptoms of schizophrenia supports this diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Schizophrenia is incorrect because the patient does not exhibit thought disorder, disorganized behavior, or multiple delusions, which are hallmarks of schizophrenia.
**Option B:** Bipolar disorder is incorrect because the patient's symptoms do not meet the diagnostic criteria for a manic or hypomanic episode, and there is no mention of mood swings or other symptoms associated with bipolar disorder.
**Option C:** Post-traumatic stress disorder (PTSD) is incorrect because the patient's symptoms do not involve flashbacks, nightmares, or avoidance behaviors typically seen in PTSD.

**Clinical Pearl / High-Yield Fact**
Delusional disorder is a chronic condition that can be challenging to treat, but cognitive-behavioral therapy and antipsychotic medications can help manage symptoms.

**Correct Answer: C. Delusional disorder**

✓ Correct Answer: B. Persistent delusion disorder