A 32-year-old woman presents to the psychiatry clinic with her husband, who reports that she has become increasingly suspicious of his fidelity over the past 3 years despite no evidence of infidelity. She frequently checks his phone, questions his whereabouts, and has accused him of having affairs with her friends and colleagues. She is preoccupied with these suspicions and has lost trust in several relationships. She denies hallucinations or delusions unrelated to infidelity. Her mood is euthymic, and she has no history of mood episodes. She works as an accountant and maintains her job performance. What is the most likely diagnosis?

Explanation

## Diagnosis: Paranoid Personality Disorder ### Key Clinical Features **Key Point:** Paranoid personality disorder (PPD) is characterized by a pervasive pattern of distrust and suspiciousness of others, interpreting their motives as malevolent. This patient demonstrates the core features: 1. **Persistent suspiciousness** — unwarranted doubts about the fidelity of her spouse 2. **Preoccupation with hidden motives** — interpreting neutral actions (checking phone, questioning whereabouts) as evidence of betrayal 3. **Reluctance to confide** — loss of trust in relationships 4. **Absence of psychosis** — no hallucinations or delusions unrelated to the theme of infidelity 5. **Functional preservation** — maintains job performance (distinguishes from delusional disorder) ### Diagnostic Criteria (DSM-5) At least 4 of the following in various contexts: - Suspects others of exploiting, harming, or deceiving them - Preoccupied with unjustified doubts about loyalty or trustworthiness - Reluctant to confide in others - Reads hidden demeaning or threatening meanings into benign remarks - Bears grudges; unforgiving of insults or slights - Perceives attacks on their character not apparent to others; quick to counterattack - Recurrent suspicions regarding fidelity of spouse or partner ### Cluster A Classification **High-Yield:** Paranoid PD is a **Cluster A disorder** (odd, eccentric, suspicious). Cluster A disorders include: - Paranoid PD (distrust, suspicion) - Schizoid PD (social withdrawal, emotional detachment) - Schizotypal PD (magical thinking, odd beliefs, social anxiety) ### Differential from Delusional Disorder **Clinical Pearl:** The absence of fixed, unshakeable false beliefs and preserved insight into the possibility of her suspicions being unfounded distinguish PPD from delusional disorder. In delusional disorder, the belief would be held with absolute conviction and would impair functioning more severely. ### Differential from Borderline PD **Warning:** Borderline PD also involves intense fear of abandonment and relationship instability, but the primary feature is emotional dysregulation, impulsivity, and identity disturbance — not pervasive suspiciousness. Borderline patients have unstable moods; this patient is euthymic. [cite:DSM-5 Personality Disorders]