Psychogenic Itch Responding to Topiramate

Itch (or pruritus) is defined as an unpleasant sensation inducing the desire of scratch. Chronic pruritus ( 6weeks duration) is a major and distressing symptom of many dermatological, systemic, neurological, or psychogenic diseases. A recent study assessed that patients with chronic pruritus carry a significant burden of disease with a substantial impact on quality of life that may be comparable to that of chronic pain. According to the neurophysiologic classification, pruritus can be classified into four major types: pruritoceptive, when itch fibers are activated by pruritogens that stimulate their sensory ending; neuropathic, due to primary lesion or dysfunction along the afferent fibers; neurogenic, generated by central mediators without neuronal damage; and psychogenic, when resulting from a pure central psychic processing in the absence of skin pathology or underlying medical disease. Hence, psychogenic pruritus (PP) is often a diagnosis of exclusion after other possible causes of pruritus have been ruled out. In particular, both PP and neuropathic itch present with no evidence of primary cutaneous lesions (pruritus sine materia), therefore clinical presentation and strategies of treatment can partially overlap. Psychiatric disturbances are common in patients who suffer from chronic itch, revealing a high psychiatric comorbidity in this population. PP can occur along with a known psychological abnormality or concurrently in patients suffering from other types of itch. While PP incidence in the general population is unknown, its incidence in patients seen in dermatology clinics is about 2%. Moreover, there is a female predominance with an average age of onset between 30 and 45 years of age. The typical clinical findings associated with psychogenic pruritus can vary considerably from superficial excoriations, erosions, or even ulcers to thickened hyperpigmented nodules and atrophic scars. Lesions are commonly found on body areas that are most accessible to the hand