Psychiatrists usually group personality disorders into three groups or clusters; clusters A, B, and C ; narcissistic personality disorder falls under the cluster. A narcissistic personality disorder is a behavioral disorder where a person feels an overly increased sense of self-importance, a condition that affects how you reason, manage situations in life, handle relationships, and your emotional intelligence. Individuals diagnosed with this kind of disorder dream about limitless wins; they also crave excessive attention and admiration. It is common in men than in women.
The medical doctor uses approved methods to determine what kind of personality disorder a person is suffering from to make a diagnosis. These methods are; international Classification of Diseases (ICD-10)  produced by the World Health Organization (WHO) and the Diagnostic and statistical manual (DSM-5)  produced by the American psychiatric association.
A critical factor in diagnosing narcissistic personality disorder is the symptoms the patient shows. Depending on how affected an individual is, the symptoms shown could differ.
Symptoms of Narcissistic personality disorder include: