Under the Surface: A Case of Secondary Delusional Infestation With Mood-Congruent Psychotic Features in a 56-Year-Old Woman.

Delusional infestation (DI) is an uncommon phenomenological syndrome characterized by the fixed, false conviction of being infested by living organisms, which often results in significant disease burden through social isolation and self-destructive behaviors. This case explores a 56-year-old woman with HIV and a history of bipolar disorder who presented with suicidal ideation and profound distress attributed to a believed parasitic infestation following a recent dose escalation of her prescribed amphetamine. The patient exhibited classic manic features, including hypergraphia and pressured speech, alongside formication and extensive scalp excoriations complicated by a secondary Pseudomonas aeruginosa wound infection. A thorough workup, including a CD4 count of 515 cells/μL and neuroimaging, effectively excluded organic etiologies and HIV-associated opportunistic infections, confirming a diagnosis of bipolar I disorder, current manic episode with mood-congruent psychotic features, with delusional infestation as the predominant psychotic content, likely exacerbated by stimulant uptitration. Management focused on a multidisciplinary approach utilizing divalproex sodium for mood stabilization and olanzapine for its antipsychotic and sedative effects, while amphetamines were discontinued. By employing a communication strategy of "empathetic neutrality," which involved validating the patient's distress without confirming the delusion, the clinical team established a therapeutic alliance that fostered cognitive flexibility. By discharge, the patient demonstrated a significant reduction in distress and improved functionality, even as a degree of delusional conviction persisted. This case highlights the importance of the dopaminergic hypothesis in DI pathophysiology and illustrates that clinical success in such complex cases is often defined by reduced morbidity and improved quality of life rather than the total eradication of the delusion. It contributes to the limited literature regarding the interplay of comorbid bipolar disorder, stimulant use, and secondary DI.