**Core Concept**
Formication and delusion of persecution are somatic and psychiatric symptoms, respectively, often seen in psychiatric and neurological disorders. These symptoms are manifestations of altered brain chemistry and function, particularly involving the serotonin and dopamine systems.

**Why the Correct Answer is Right**
The combination of formication and delusion of persecution is characteristic of **Delusional Parasitosis (DP)**. In DP, patients experience tactile hallucinations (formication) and believe that they are infested with parasites or insects. This delusional thinking is often accompanied by a fixed belief in the presence of parasites, despite medical examination and reassurance. The pathophysiology of DP is thought to involve abnormalities in the serotonin and dopamine systems, particularly in the brain's limbic and mesolimbic regions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because formication and delusion of persecution are not typically seen together in **Bipolar Disorder**, although mood disorders can present with somatic and psychotic symptoms. However, the combination of formication and delusional thinking is more specific to Delusional Parasitosis.

**Option B:** This option is incorrect because **Schizophrenia** can present with a range of psychotic symptoms, including delusions. However, formication is not a typical symptom of schizophrenia, and the combination of formication and delusional thinking is more characteristic of Delusional Parasitosis.

**Option C:** This option is incorrect because **Alzheimer's Disease** is a neurodegenerative disorder characterized by cognitive decline, memory loss, and behavioral changes. While patients with Alzheimer's may experience hallucinations, formication is not a typical symptom, and the combination of formication and delusional thinking is more specific to Delusional Parasitosis.

**Option D:** This option is incorrect because **Substance-induced Psychosis** can present with a range of psychotic symptoms, including delusions. However, formication is not a typical symptom of substance-induced psychosis, and the combination of formication and delusional thinking is more characteristic of Delusional Parasitosis.

**Clinical Pearl / High-Yield Fact**
Delusional Parasitosis is often misdiagnosed as a skin condition or a psychiatric disorder, leading to unnecessary treatments. A thorough medical and psychiatric evaluation is essential to diagnose and manage this condition.

**Correct Answer:** C.