**Question:** Delusion in which the person believes the he is suffering from some serious illness is

A. Delusional disorder
B. Schizophrenia
C. Schizoaffective disorder
D. Dissociative disorder

**Core Concept:** Delusions are fixed, false beliefs that are not based on reality and are resistant to logical argumentation. They are a core feature of psychotic disorders.

**Why the Correct Answer is Right:** The correct answer is Delusional disorder, which is characterized by persistent, fixed ideas or beliefs that are not based on reality and do not coincide with the patient's age, culture, or social status. In this case, the delusion is related to the person's own health condition and leads them to believe they have a serious illness.

**Why Each Wrong Option is Incorrect:**

A. Schizophrenia: Schizophrenia involves a range of symptoms, including disorganized thinking, hallucinations, and paranoia, but the delusions are not specifically about the person's own health condition.
B. Schizoaffective disorder: This disorder combines psychotic symptoms with mood disturbances (mania or depression), but the delusion is not specifically about the person's own health condition.
C. Dissociative disorder: Dissociative disorders involve a dissociation of identity or a sense of self, not specifically about the person's own health condition.

**Clinical Pearl:** It is essential for medical students and healthcare professionals to understand the difference between various mental health disorders, including their core features and distinguishing characteristics. Recognizing these distinctions helps in providing appropriate diagnosis, treatment, and support to patients with delusional disorders.

**Correct Answer:** D. Delusional disorder

Delusional disorder is a specific type of delusion where the patient has a persistent belief that is not based on reality and does not coincide with the patient's age, culture, or social status. In this case, the delusion is specifically about the person's own health condition. This type of delusion can lead to intense fear and anxiety related to the imagined illness, leading to unnecessary medical consultations and expensive medical tests.