Psychogenic Pruritus: A Review

by

Stephanie Hu

Boston, MA, USA

on November 17, 2008

4th year Medical Student, Harvard Medical School, Boston, MA, USA

Case Presentation ( David Elpern M.D.) :

This 56 yo woman has a two year history of intense pruritus. She dates the onset to when she was exposed to toxic fumes at work. Since then, she wakes at night excoriating her skin. Other than a mild anemia and eosinophilia, all studies have been unremarkable. She has not worked for the past two years. The is an intelligent person. Divorced, mother of three adult children (one with Turner's Syndrome) she worked in retail and latterly as a security guard. Skin biopsy was not helpful.  Subsequent questioning reveals history of sexual abuse as a child and profound depression.

Reason for presentation:

This sad looking woman is illustrative of some patients that present to us with idiopathic pruritus. She has "The Impulsive Type" described below. After thorough workups by primary care physicians, allergists, dermatologists and often other practitioners, one is left with the diagnosis of "psychogenic pruritus with excoriations." Even with the best therapies these patients are often recalcitrant to therapy. Ms. Hu's paper will help us to understand these patients and formulate therapeutic strategies. Your comments are welcome.

 

Introduction: the Relationship between the Psyche and the Skin

The skin is readily available for inspection and manipulation at any time and can serve, for many patients, as the physical manifestation of their inner psyche

- Considerable evidence suggests that psychologic and psychiatric factors can augment or diminish the sensation of itching (i.e., both mental stress and depression enhance the perception of pruritus)

- A patient’s personality and coping mechanisms may play an important role in the translation of stress into physical dermatologic signs like pruritus

The connection between skin disease and the psyche should not be underestimated

- The liaison among primary care physicians, psychiatrists, and dermatologists can be of great value in the management of these complex patients

Biological Mechanisms of Pruritus

The sensation of pruritus can be provoked by different exogenous agents, including mechanical, electrical, thermal, or chemical stimuli, as well as by endogenous causes.

Impulses are transmitted through specialized itch receptors superficial to those responsible for pain --> specific non-myelinated C fibers --> dorsal horn of the spinal cord --> anterolateral spinothalamic tract --> postcentral gyrus of the cerebral cortex

Endogenous chemical mediators include

o 5HT: regulatory role at supraspinal level and modulation of 5HT3 receptors in dorsal root ganglia (ondansetron found to be effective in Rx of opioid-induced pruritus)

o Histamine: one of the most important peripheral mediators; acts on H1 receptors and directly on epidermal nerve endings to cause pruritus

o Prostaglandin E2 (PGE2): causes pruritus by decreasing threshold of 5HT and releasing histamine

o Neuropeptides (e.g., endogenous opioids, including methionine enkephalin, leucine enkephalin, and β-endorphin)

 Peripherally, mechanisms by which opioids may intensify pruritus include augmentation of histamine’s actions and the production of inflammatory reactions via immune-mediated phenomena

 Central opioids can evoke or augment pruritus independent of their histamine-releasing effect (opiate agonists, such as morphine, can cause itch, while opiate antagonists, such as naloxone, can relieve pruritus)

Definition and Classifications of Psychogenic Pruritus (PP)

- Psychogenic pruritus (PP) is diagnosed when pruritus occurs in the absence of skin pathology or an underlying medical disease, and can thus be classified as being primarily psychogenic in nature

- PP may also occur in conjunction with pruritus due to primary skin disease or systemic illnesses

-PP is characterized as an excessive impulse to scratch, gouge, or pick at normal skin

- There is often a cycle of cutaneous trauma caused by excoriation that leads to skin lichenification, which in turn causes increased Sx’s of pruritus - can be difficult to establish whether itch or scratch came first

- Patients with PP exhibit heterogeneous behavior that can span a compulsivity-impulsivity continuum from purely obsessive-compulsive to purely impulsive, with mixed Sx’s between these poles

Table 1. Subtypes of Psychogenic Pruritus

Compulsive type	Impulsive type	Mixed type
1. Skin excoriation is performed to avoid increased anxiety or to prevent a dreaded event or situation and/or is elicited by an obsession (i.e., obsession about contamination of skin)	1. Skin excoriation associated with arousal, pleasure, or reduction of tension	1. Skin excoriation has both compulsive and impulsive features
2. It is performed in full awareness	2. It is performed at times with minimal awareness (i.e., automatically)
3. It is associated with some resistance to performing the behavior	3. It is associated with little resistance to performing the behavior
4. There is some insight into its senselessness or harmfulness	4. There is little insight into its senselessness or harmfulness
Examples: delusions of parasitosis and other forms of MHP, neurotic excoriations, and cutaneous compulsions	Examples: depression-induced, anxiety-induced, chronic tactile hallucinosis

Epidemiology of PP

- Incidence of PP in the general population is unknown; however, its incidence is 2% in patients seen in dermatology clinics

- There is a female predominance with average age of onset between 30 and 45 years of age

Psychiatric Co-Morbidities of PP: Clues to Etiology

- Depression, anxiety, somatoform disorders, mania, psychosis, and substance abuse have been associated with itch

o Some studies suggest depression may be the primary clinical state in PP

o Body dysmorphic disorder, trichotillomania, kleptomania, and borderline personality were also reported in patients with PP

o One recent study in 360 patients postulated that itching, like pain and numbness, may be a symptom of somatoform dissociation

o Another study found that 32% of hospitalized patients with schizophrenia and affective disorders reported suffering from itch after other causes of itch were ruled out --> suggests that PP may be a common Sx among psychiatric patients

- OCD is a common co-morbid condition in psychogenic pruritus

o Pruritus associated with obsessive-compulsive spectrum disorder is characterized as that of recurrent, intrusive thoughts that lead to compulsive skin picking, hair pulling, and excoriations

o Mast cell degranulation and cytokine release is seen with the itch-scratch cycle --> recurrent itching can lead to an itch-scratch cycle releasing pruritogenic factors, further contributing to the obsessive-compulsive interplay

Clinical Features of PP

- The secondary skin changes associated with PP are commonly found on body areas that are most accessible to the hand, such as extensor sources of the arms and legs, abdomen, thighs, and upper parts of the back and shoulders, with the face being the most common site

- The secondary skin signs may be in varying stages of evolution and may vary in number from a few to several hundred;

o Often, patients report picking, rubbing, scratching, or inserting objects to relieve the pruritus --> lesions may be painful, bleed, and ulcerate with delayed healing due to recurrent picking.

o However, the itch could also occur without any skin signs

- Patients suffer from low self image and have difficulties coping with aggression; also experience shame or embarrassment about behavior and often do not disclose habit to doctors or relatives

- Clues for psychogenic etiology of pruritus

o Autoerotic pruritus: pt derives pleasure from the itch-scratch cycle --> The pruritus is thought from a psychoanalytic viewpoint to be the expression of an unconscious sexual drive

o Paroxysmal pruritus: occurs in short bursts as opposed to a more chronic pattern of itching, and may indicate a psychogenic process (although this can be present in neurogenic pruritus as well)

o PP is typically associated with cessation of Sx’s during sleep

Diagnosis

- PP is a Dx of exclusion and can be made after ruling out other causes of pruritus (i.e., due to systemic or dermatologic disease) that may mimic this condition

- No clear definition of PP in the DSM-IV (term “psychogenic pruritus” is not used),

The French Psychodermatology Group proposed the following diagnostic criteria for PP:

3 compulsory criteria

1. Localised or generalised pruritus sine materia ( without primary skin lesions0
2. Chronic pruritus (>6 weeks)
3. No somatic cause

3/7 optional cirteria

1. A chronological relationship of pruritus with one or several life events that could have psychological repercussions
2. Variations in intensity associated with stress
3. nocturnal variations
4. prominance during rest or inaction
5. Associated psychological disorder
6. Pruritus that could be improved by psychotropic drugs
7. Pruritus that could be improved by psychotherapy

Therapeutic Options for PP

• Three categories of therapeutic options are available for pts with PP:
• CNS-specific therapy (choice depends on the underlying psychopathology)
• Doxepin
• Rx of choice for PP provoked by underlying depression; also used for neurotic excoriations and cutaneous compulsions
• Alprazolam
• Most beneficial when underlying psychopathology for the pruritus is anxiety
• Buspirone
• Also useful for anxiety-induced PP
• Pimozide
• Rx of choice for delusions of parasitosis and other forms of MHP
• Atypical antipsychotics (i.e., risperidone)
• Have been used to treat pts with delusions of parasitosis
• TCA’s (i.e., clomipramine)
• Effective against the obsessive-compulsive behavior and co-existing depression seen with neurotic excoriations and cutaneous compulsions
• SSRI’s (i.e., fluoxetine, fluvoxamine, sertraline, paroxetine)
• May benefit both pruritus and depression and have less association with side effects such as sedation and cardiac conduction problems
• Effective against the obsessive-compulsive behavior and co-existing depression seen with neurotic excoriations and cutaneous compulsions
• Paroxetine is esp. useful in pts w/ OCD
• Opioid antagonists (i.e., naltrexone)
• Shown to be effective against some cases of central pruritus
• Ondansetron
• Topical therapy
• May be less effective due to predominantly central nature of the pruritus in PP, but may be used empirically to distinguish central from peripheral cause, and may enhance effects of centrally active agents in conditions with both components
• Agents:
• Doxepin cream
• Capsaicin cream
• Topical anesthetic cream (EMLA, pramoxine)
• Supportive therapy
• Can be combined with any of the above treatments to provide symptomatic relief, augmenting anti-pruritic activity and increasing patient comfort
• Agents:
• Emollients (compounds with urea 5-10%, lipid preparations, ammonium lactate lotion)
• Menthol 0.5-2% and camphor 0.2-5% lotions
• Cold compresses with moisturizers
• Occlusion with Unnaboot, Duoderm, or malleable (non-latex) gloves
• Intralesional steroid injection
• Laser therapy
• Cryotherapy
• Goeckerman therapy
• UV (light) therapy (UVB or PUVA)
• Non-pharmacologic management may include psychotherapy, hypnosis, relaxation training, biofeedback, operant conditioning, cognitive-behavioral therapy, meditation, affirmation, stress management, and guided imagery
• The impact of such treatments for pruritus is unclear at this point, although these modalities have been successful by some reports

References

1. Arnold LM, Auchenbach MB, McElroy SL.  Psychogenic excoriation: clinical features, proposed diagnostic criteria, epidemiology, and approaches to treatment.  CNS Drugs 2001; 15: 351-359.
2. Krishnan A, Koo J.  Psyche, opioids, and itch: therapeutic consequences.  Dermatologic Therapy 2005; 18: 314-322.
3. Yosipovitch G, Samuel LS.  Neuropathic and psychogenic itch.  Dermatologic Therapy 2008; 21: 32-41. 
4. Misery L, Alexandre S, Dutray S, Chastaing M, Consoli SG, Audra H, et al.  Functional itch disorder or psychogenic pruritus: suggested diagnosis criteria from the French Psychodermatology Group.  Acta Derm Venereol 2007; 87: 341-344.
5. Shaw RJ, Dayal S, Good J, Bruckner AL, Joshi SV.  Psychiatric medications for the treatment of pruritus.  Psychosom Med 2007; 69: 970-978.
6. Koo JY, Ng TC.   Psychotropic and neurotropic agents in dermatology: unapproved uses, dosages, or indications.   Clin Dermatol. 2002 Sep-Oct;20(5):582-94.
   

   Table 2.  CNS-Specific Therapy for Psychogenic Pruritus (adapted from Krishnan A, Koo J. Psyche, opioids, and itch: therapeutic consequences. Dermatologic Therapy 2005; 18: 314-322)