A woman believes she has “chronic scabies” despite repeated treatments. What is the most likely diagnosis?

The most likely diagnosis for a woman who believes she has "chronic scabies" despite receiving repeated treatments is delusional disorder. In this context, the woman exhibits a fixed false belief that she is suffering from a condition that has been effectively addressed, indicating a delusion. Delusional disorder is characterized by the presence of one or more delusions that persist for a month or longer, and in this case, the belief about chronic scabies fits that description.

This belief persists regardless of contrary evidence, such as the repeated treatments that should have alleviated her symptoms. While it’s necessary to consider other diagnoses, such as schizophrenia, which involves a broader range of symptoms including hallucinations and disorganized thinking, the specific focus on a delusion related to a skin condition is more consistent with delusional disorder.

In contrast, schizotypal personality disorder involves eccentric behavior and thinking but lacks the fixed false beliefs characteristic of delusional disorder. The option of widespread scabies suggests an actual medical condition rather than a belief, which also does not align with her fixed conviction regardless of treatment outcomes.