A 26-year-old man is firmly convinced that his hands are contaminated with lethal bacteria despite repeatedly negative cultures. He washes his hands dozens of times daily, has no hallucinations, no formal thought disorder, and functions reasonably between washing episodes. He rejects all reassurance. What is the most appropriate diagnosis?

• A Delusional disorder, somatic type
• B Schizophrenia, paranoid type
• C Illness anxiety disorder
• D Obsessive-compulsive disorder with absent insight or delusional beliefs specifier ✓

Explanation

DSM-5 explicitly allows OCD to be diagnosed even when insight is absent and beliefs are held with delusional intensity, using the absent insight or delusional beliefs specifier. The presence of classic contamination obsessions and washing compulsions keeps the case within OCD rather than delusional disorder. Illness anxiety disorder is excluded because there are true repetitive compulsive rituals centred on contamination fear, not preoccupation with having an illness. Schizophrenia is unsupported by any other psychotic features.

Reference: Diagnostic and Statistical Manual of Mental Disorders, DSM-5 ed.

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Written and medically reviewed by the StethoPrep medical team.