I’ve got a really talented group of trainees this past month and Leah Laageide gave a fantastic Clinical Problems in Consultation Psychiatry (CPCP) on Psychogenic Pruritus. She’s interested in Dermatology and is working on research project already with one of the Dermatology faculty.
In fact, she had more than one presentation she volunteered to deliver. The other was on Neurodermatitis, which was also fascinating and was on Lichen Simplex Chronicus. Although I’m a general hospital psychiatrist, I occasionally get called to various outpatient clinics, and Dermatology is one of them. Psychiatric problems involving the skin are not uncommon. One of the more challenging issues is Delusional Disorder, somatic type, one example of which is delusional parasitosis. There was an excellent recently published review:
Vulink, N. C. (2016). “Delusional Infestation: State of the Art.” Acta Derm Venereol 96(217): 58-63.
Patients with a delusional infestation (DI) have an overwhelming conviction that they are being infested with (non) pathogens without any medical proof. The patients need a systematic psychiatric and dermatological evaluation to assess any possible underlying cause that could be treated. Because they avoid psychiatrists, a close collaboration of dermatologists and psychiatrists, who examine the patient together, seems to be a promising solution. It helps to start a trustful doctor-patient relationship and motivates the patient for psychiatric treatment. We here review diagnostic criteria, classification of symptoms, pathophysiology and treatment options of DI. Antipsychotic medication is the treatment of choice when any other underlying cause or disorder is excluded. Further research is needed to assess the pathophysiology, and other treatment options for patients with DI.
This particular disorder may also include so-called Morgellons disease, in which patients complain of similar symptoms and about which there is some controversy as to whether or not it’s primarily a psychiatric disorder. As for the neurobiology of DI, research seems to show that it’s correlated with disrupted medial prefrontal control over somato-sensory representations. And as Leah points out, multiple brain regions may be involved in the genesis of pruritus.
Paus, R., et al. (2006). “Frontiers in pruritus research: scratching the brain for more effective itch therapy.” J Clin Invest 116(5): 1174-1186.
This Review highlights selected frontiers in pruritus research and focuses on recently attained insights into the neurophysiological, neuroimmunological, and neuroendocrine mechanisms underlying skin-derived itch (pruritogenic pruritus), which may affect future antipruritic strategies. Special attention is paid to newly identified itch-specific neuronal pathways in the spinothalamic tract that are distinct from pain pathways and to CNS regions that process peripheral pruritogenic stimuli. In addition, the relation between itch and pain is discussed, with emphasis on how the intimate contacts between these closely related yet distinct sensory phenomena may be exploited therapeutically. Furthermore, newly identified or unduly neglected intracutaneous itch mediators (e.g., endovanilloids, proteases, cannabinoids, opioids, neurotrophins, and cytokines) and relevant receptors (e.g., vanilloid receptor channels and proteinase-activated, cannabinoid, opioid, cytokine, and new histamine receptors) are discussed. In summarizing promising new avenues for managing itch more effectively, we advocate therapeutic approaches that strive for the combination of peripherally active antiinflammatory agents with drugs that counteract chronic central itch sensitization.
Shaw, R. J., et al. (2007). “Psychiatric medications for the treatment of pruritus.” Psychosom Med 69(9): 970-978.
OBJECTIVES: To review the use of psychiatric medications in the treatment of pruritus. METHODS: A literature review was conducted using the key words pruritus, psychiatric, and treatment. RESULTS: Three categories of pruritus are described: dermatologic, systemic, and psychogenic. Peripheral and central nervous system mechanisms of pruritus are reviewed. Conventional dermatologic treatments for pruritus are contrasted with some of the common psychopharmacologic treatment modalities that include anxiolytic, antidepressant, and antipsychotic agents. A treatment algorithm is offered to help guide the treatment of patients with pruritus. CONCLUSIONS: Psychiatric medications have been used successfully in the treatment of pruritus that is associated with both psychocutaneous and systemic disorders, which are resistant to conventional treatment.
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