Scratching increases epidermal neuronal branching and alters psychophysical testing responses in atopic dermatitis and brachioradial pruritus

Background

Chronic scratching imposes a major stress on the skin and can lead to itch intensity worsening, and consequently, patients may enter an itch-scratch cycle. This repetitive mechanical stress can result in lichenification, worsening of epidermal barrier function, and enhanced cutaneous inflammation. Furthermore, a reduction of intraepidermal nerve fibers was previously described in lichenification.

Aim

The aim of this study was to investigate the influence of chronic scratching on the epidermal neuroanatomy and on sensory changes, in particular the prevalence of hyperknesis and alloknesis in patients after mechanical, chemical, and electrical stimuli.

Methods

Analyses were performed on pruritic lichenified (chronically scratched), pruritic non-lichenified (not chronically scratched), and non-pruritic non-lesional (unaffected) skin areas of patients with inflammatory pruritus, i.e., atopic dermatitis (n = 35), and neuropathic pruritus, i.e., brachioradial pruritus (n = 34) vs. healthy matched controls (n = 64). Our fine-grained spatial skin characterization enabled specifically studying the differential effects of chronic scratching in inflammatory and neuropathic itch.

Results

Analysis of intraepidermal nerve fiber density showed rarefaction of fibers in all three skin areas of patients compared with healthy controls in both diagnoses. Even more, the two pruritic areas had significantly less nerve fibers than the unaffected skin, whereas electrically induced itch was massively increased. Epidermal branching of the remaining nerve fibers in lichenified/chronically scratched skin was increased, particularly in patients with brachioradial pruritus, which may contribute to the pronounced local neuronal sensitivity. Hyperknesis and alloknesis were found to increase independently of lichenification.

Conclusion

Our results indicate that chronic scratching may not affect intraepidermal nerve fiber density but leads to a stronger branching pattern of intraepidermal nerve fibers, which may contribute to local hypersensitivity. The increased sensitivity in the pruritic areas suggests mechanisms of peripheral sensitization, whereas the increased sensation of electrically and chemically induced itch in unaffected skin indicates central sensitization for itch.

Persistent dysesthesias in involuted infantile hemangiomas: An uncommon complication in a common condition

BACKGROUND/OBJECTIVES

Infantile hemangiomas (IHs) are common benign vascular tumors of infancy. IHs tend to grow in the first few months of life and then gradually involute over years, often leaving fibrofatty residua or textural changes in their place. Classically, these lesions are painless throughout their entire natural history; however, we now report on seven patients with involuted IH with intermittent but persistent sensory symptoms.

METHODS

This is a multicenter case series in which members of the Birthmarks Focused Study Group of the Pediatric Dermatology Research Alliance (PeDRA) and the Hemangioma Investigator Group contributed patients with IH and dysesthesias from their clinical practices. Charts were then reviewed to document clinical details.

RESULTS

Seven patients were included, presenting at an average age of 14.6 years (range 3-48 years) for complaints related to discomfort in the region of involuted IH. The majority (6/7) reported pain or tenderness to the area. One patient reported pruritus. All patients reported intermittent symptoms. The length of symptoms ranged between 4 months and 5 years. Treatment was attempted in 5/7 patients. Ice, oral propranolol, topical capsaicin, and intralesional triamcinolone partially improved symptoms.

CONCLUSIONS

Persistent cutaneous dysesthesias were present in seven patients, in most cases many years after completion of involution. Further research is needed to fully elucidate the pathophysiology and optimal treatments for this IH complication.