Undiagnosed Delusional Infestation Leading to Severe Self-Inflicted Injuries: A Case Report

Delusional infestation (DI), or delusional disorder, somatic type, is a rare psychiatric condition characterized by a fixed false belief of infestation despite lack of medical evidence. Patients frequently resist psychiatric care due to poor insight and somatic preoccupation, increasing the risk of delayed diagnosis and serious self-harm.

We report the case of a 60-year-old woman with no prior psychiatric history who presented with 11.5% total body surface area (TBSA) second- and third-degree self-inflicted burns resulting from attempts to eradicate perceived skin parasites. She reported a 2-year history of pruritus attributed to "shiny fiberglass bacteria," with associated tactile hallucinations. Extensive medical workup excluded underlying anatomic, inflammatory, or infectious etiologies. The psychiatry consultant diagnosed her with delusional disorder, somatic type. Treatment with low-dose risperidone and doxepin was initiated following empathic, nonconfrontational engagement. Her distress improved, and she demonstrated early signs of insight by the time of hospital discharge.

This case highlights the risk of severe self-injury in DI and underscores the need for timely psychiatric evaluation and a compassionate, collaborative approach. Reframing treatment goals to prioritize symptom relief over delusional challenge may enhance engagement and facilitate recovery.