Consensus recommendations for the diagnosis and management of delusional infestation: A Delphi study

Delusional infestation (DI) is a psychiatric disorder defined as a fixed false belief of being infested with animate or inanimate material in the absence of objective medical evidence. It presents frequently to dermatology and psychiatry and poses diagnostic and communication challenges.

To develop a Delphi consensus on the definition, diagnostic work-up and management of DI.

Under the auspices of the European Society for Dermatology and Psychiatry (ESDaP), a core expert group drafted 22 statements based on prior survey data and the literature. International experts in DI (dermatology, psychiatry, tropical medicine) participated in two anonymous e-Delphi rounds followed by a consensus meeting. Consensus was predefined as ≥ 75% agreement or disagreement.

Of 47 invited experts, 37 completed round 1 and 34 round 2; 23 joined the final meeting. Consensus was reached for 20/22 statements. Agreements included: (i) defining DI as a psychiatric disorder with fixed beliefs of infestation; (ii) distinguishing primary versus secondary DI; (iii) acknowledging quality-of-life impairment; (iv) examining patient-provided material as useful diagnostically and for rapport; (v) considering blood tests, urine toxicology and selective neuroimaging when indicated; (vi) early and concurrent management of psychiatric and cutaneous aspects; (vii) antipsychotics as first-line treatment, with choice guided by evidence and patient factors; (viii) limited role for long-acting depot formulations and CBT; (ix) importance of dermatology-psychiatry collaboration; and (x) using adapted terminology with patients while ensuring informed consent for antipsychotic prescribing. Non-consensus items concerned explicitly naming the diagnosis to patients and routine use of standardized outcome scales.

This international Delphi consensus statement provides practical, expert-informed recommendations for the assessment and management of DI, and is intended to inform future research and formal guideline development.