Cognitive theorists believe the disorder to be a result of an underlying belief that other people are unfriendly in combination with a lack of self-awareness. Diagnosis
ICD-10
The World Health Organizations ICD-10 lists paranoid personality disorder under (F60.0). It is a requirement of ICD-10 that a diagnosis of any specific personality disorder also satisfies a set of general personality disorder criteria. It is also pointed out that for different cultures it may be necessary to develop specific sets of criteria with regard to social norms, rules and other obligations.PPD is characterized by at least three of the following symptoms:

excessive sensitivity to setbacks and rebuffs;
tendency to bear grudges persistently (i.e. refusal to forgive insults and injuries or slights);
suspiciousness and a pervasive tendency to distort experience by misconstruing the neutral or friendly actions of others as hostile or contemptuous;
a combative and tenacious sense of self-righteousness out of keeping with the actual situation;
recurrent suspicions, without justification, regarding sexual fidelity of spouse or sexual partner;
tendency to experience excessive self-aggrandizing, manifest in a persistent self-referential attitude;
preoccupation with unsubstantiated "conspiratorial" explanations of events both immediate to the patient and in the world at large.Includes: expansive paranoid, fanatic, querulant and sensitive paranoid personality disorder. Excludes: delusional disorder and schizophrenia. DSM-5
The American Psychiatric Associations DSM-5 has similar criteria for paranoid personality disorder. They require in general the presence of lasting distrust and suspicion of others, interpreting their motives as malevolent, from an early adult age, occurring in a range of situations.
Diagnosis
PSC is generally diagnosed on the basis of having at least two of three clinical criteria after secondary causes of sclerosing cholangitis have been ruled out:
serum alkaline phosphatase (ALP) > 1.5x the upper limit of normal for longer than 6 months
cholangiography demonstrating biliary strictures or irregularity consistent with PSC
liver biopsy consistent with PSC (if available)Historically, a cholangiogram would be obtained via endoscopic retrograde cholangiopancreatography (ERCP), which typically reveals "beading" (alternating strictures and dilation) of the bile ducts inside and/or outside the liver. Currently, the preferred option for diagnostic cholangiography, given its noninvasive yet highly accurate nature, is magnetic resonance cholangiopancreatography (MRCP), a magnetic resonance imaging technique. MRCP has unique strengths, including high spatial resolution, and can even be used to visualize the biliary tract of small animal models of PSC.Most people with PSC have evidence of autoantibodies and abnormal immunoglobulin levels. For example, approximately 80% of people with PSC have perinuclear antineutrophil cytoplasmic antibodies (P-ANCA); however, this and other immunoglobulin findings are not specific to those with PSC and are of unclear clinical significance/consequence. Antinuclear antibodies and anti-smooth muscle antibody are found in 20-50% of PSC patients, and likewise are not specific for the disease,but may identify a subgroup of PSC patients who also have autoimmune hepatitis (i.e. PSC-AIH overlap syndrome).The differential diagnosis can include primary biliary cholangitis (formerly referred to as primary biliary cirrhosis), drug-induced cholestasis, cholangiocarcinoma, IgG4-related disease, post-liver transplantation nonanastomotic biliary strictures,  and HIV-associated cholangiopathy.