High-dose doxepin for the treatment of chronic, intractable scalp pruritus

Itch: Pathogenesis and treatment

Itch pathogenesis is broadly characterized into histaminergic and nonhistaminergic pathways and transmitted via 2 main receptor families: G protein-coupled receptors and transient receptor potential channels. In the skin, itch is primarily transmitted by unmyelinated type C and thinly myelinated type Aδ nerve fibers. Crosstalk between the immune and neural systems modulates itch transmission at the skin, spinal cord, and brain. Among the many known pruritogens, Th2 cytokines, such as interleukin-4, interleukin-13, interleukin-31, and thymic stromal lymphopoietin, are particularly important mediators that signal through shared Janus kinase pathways, representing novel targets for novel itch therapeutics. Emerging evidence has also revealed that the opioidergic system is a potent modulator of itch transmission, with increased μ-opioid activity and decreased κ-opioid activity contributing to itch pathogenesis. Optimal management of itch requires that treatment approaches be tailored to specific etiologic itch subtypes. When the etiology is unknown and patients are given a diagnosis of chronic pruritus of unknown origin, treatment should be guided by the presence of Th2 polarization, often reflected by increased blood eosinophils. In the second article of this 2-part series, we outline our current understanding of itch pathogenesis and discuss available and emerging treatments for itch.

Scalp dysaesthesia and lichen simplex chronicus: diagnostic and therapeutic update with literature review

Scalp dysaesthesia, considered a variant of the cutaneous dysaesthesia syndrome, is characterized by chronic sensory symptoms, including pruritus, pain, burning and stinging in a well‐defined location, without objective findings. Its aetiology is not well elucidated and treatment options are limited, thus it can be challenging and frustrating for both patient and physician. It can be associated with lichen simplex chronicus. In this paper, we review the literature on the pathogenetic factors, diagnostic methods and therapeutic options in the management of scalp dysaesthesia. Dissociation, cervical spine disease and muscle tension seem to be the most important pathogenetic factors. Trichoscopy, reflectance confocal microscopy and biopsy are all helpful for the diagnosis of the disease. Therapies include high‐potency topical or intralesional corticosteroids, capsaicin and topical anaesthetics, sedative antihistamines, tricyclic antidepressants, transcutaneous electric nerve stimulation, botulinum toxin and vitamin B12.