What is Neurogenic/Psychogenic Pruritus?
Neurogenic and psychogenic pruritus are two distinct categories of chronic itch without primary skin lesions: neurogenic pruritus arises from pathology anywhere along the afferent nervous system pathway (nerve damage or dysfunction), while psychogenic pruritus (functional itch disorder) is triggered, worsened, or sustained by psychological factors as the primary mechanism. 1, 2
Neurogenic (Neuropathic) Pruritus
Key Defining Features
- Neurogenic pruritus results from lesions or dysfunction of afferent neural pathways, presenting with characteristic sensory symptoms including burning, paresthesia, stinging, and tingling sensations. 3, 4
- The itch is typically described as a "deep" or "internal" sensation rather than superficial, often with localized distribution corresponding to a specific dermatome. 4
- Skin biopsy may reveal reduced intraepidermal nerve fiber density, confirming small fiber neuropathy when diagnosis remains uncertain. 4
Common Underlying Causes to Investigate
- Peripheral nerve compression, central nervous system lesions, small fiber neuropathy (often associated with metabolic syndrome and diabetes mellitus), and cervical spine pathology should be systematically evaluated. 3, 4
Psychogenic Pruritus (Functional Itch Disorder)
Diagnostic Criteria
The British Association of Dermatologists recognizes functional itch disorder as a distinct clinical entity with specific diagnostic criteria: 1
Compulsory criteria (all must be present):
- Generalized pruritus without visible primary skin lesions
- Chronic duration (>6 weeks)
- No somatic cause identified after thorough investigation 1
Optional criteria (at least 3 must be present):
- Chronological relationship with psychologically significant life events
- Intensity variations associated with stress
- Worsening at night 1
Psychological Mechanisms
- Pruritus can be directly triggered by psychological factors through well-documented neurological pathways, including stress activating neural circuits in the hippocampus and subcortical structures. 1
- Negative emotions (rage, fear, annoyance, embarrassment) can trigger or worsen itching through these pathways. 1
- Visual and verbal suggestion alone can elicit pruritus, demonstrating the powerful mind-body connection in this disorder. 1
- Opioids, acetylcholine, and dopamine are likely involved in mentally-induced itch phenomena. 5
Critical Distinction Between the Two
The key differentiating factor is the primary mechanism: neurogenic pruritus stems from demonstrable nerve pathology (structural or functional damage to sensory pathways), while psychogenic pruritus has psychological factors as the primary driver with no identifiable nerve damage. 2, 6
Common Pitfall to Avoid
- Patients with no primary cutaneous lesions are frequently prematurely diagnosed as having a psychiatric disorder when they may actually have neuropathic pruritus requiring neurological investigation. 3, 2
- A thorough evaluation for neuropathic causes must be completed before attributing pruritus to psychological factors alone. 3
Quality of Life Impact
- Both conditions significantly reduce quality of life in a manner comparable to chronic pain, with deranged sleep patterns, feelings of stigmatization, and distorted body image frequently developing. 1
- The psychosocial burden is substantial regardless of etiology, with anxiety and depression commonly coexisting. 4, 7