Lichen amyloidosus as a sweat gland/duct-related disorder: resolution associated with restoration of sweating disturbance

A Case Report of Generalized Non-pruritic Lichen Amyloidosis

We evaluate the rare case of a patient who presented with generalized, non-pruritic lichen amyloidosis. There are three reported cases of generalized and non-pruritic lichen amyloidosis. The lichen amyloidosis subtype of primary localized cutaneous amyloidosis is characterized by keratinocyte-derived amyloid deposition in the papillary dermis, classically presenting as pruritic, hyperpigmented macules coalescing into plaques on the lower extremities. While the pathogenesis is likely multifactorial, chronic scratching has been proposed as an inciting factor. The patient's type of lichen amyloidosis challenges the proposed etiology of chronic scratching leading to amyloid deposition.

Role of basal sweating in maintaining skin hydration in the finger: A long-standing paradox in dry skin resolved

A long-standing paradox in dermatology is why skin dehydration in the fingers can be triggered by repeated water exposure despite the action of water to hydrate skin tissue. Potential clues might be provided by identifying a mechanism through which water is held in the skin of the fingers. We speculated that this mechanism would be impaired after repeated water exposure. Here, we investigated whether there might be glabrous skin-specific water-holding machinery and whether this machinery might be impaired in dry skin/hand eczema. We examined this by using an impression-mould technique, allowing for an accurate quantification of sweat gland/duct activity and optical coherence tomography. Unlike in hairy skin, sweat pores were rarely detected at the folds of the finger at baseline. Surprisingly, after water exposure, sweat pores at the folds opened and those at the ridges closed in healthy controls (HCs). Sweating in the dermal folds of the hands correlated with skin hydration, and decreased in dry skin/hand eczema, suggesting that its impairment may be one of the causes of dry skin. After repeated water exposure, basal sweating response at the folds was exhausted in patients with dry skin/hand eczema as well as HCs. This exhaustion was rescued by exposing individuals to high humidity. Basal sweating defects would be a target for dry skin/hand eczema. Maintaining basal sweating responses in the finger is the best preventive measures in achieving prevention of dry skin/hand eczema.

Herpes simplex virus-induced murine dry skin model through sweating disturbance

BACKGROUND

Given that ocular glands become infected secondarily to herpes simplex virus 1 (HSV-1) keratitis, resulting in the loss of tear production, sweat glands may also be susceptible to HSV-1 infection, resulting in sweating disturbance, which is observed frequently in atopic dermatitis. However, due to the lack of sweat glands on the hairy skin of mice, the role of sweating in the maintenance of skin hydration has not been elucidated.

OBJECTIVE

To determine the relationship between HSV-1 infection of sweat glands and sweating disturbance-induced dry skin.

METHODS

By using the impression mold technique, we examined the sweating response together with the detection of HSV-1 DNA in the sweat glands of footpads, the only area with sweat glands in mice, after local cutaneous HSV-1 inoculation of immunocompetent mice.

RESULTS

The sweating response and skin surface hydration were significantly decreased at 7-14 days post-infection. Sweating disturbance and dry skin was markedly enhanced when HSV-1 inoculation was followed by hyperthermic stress. Both resolved spontaneously and became resistant to a second HSV-1 inoculation, associated with increased anti-HSV-IgG antibodies. HSV-1 DNA was detected in sweat glands and dorsal root ganglia. The sweating response remained decreased after subcutaneous injection with pilocarpine, correlating histologically with marked dilatation of sweat gland lumens. These findings indicate that sweating disturbance is unlikely to be the outcome of nerve damage by HSV-1 infection.

CONCLUSION

Sweating disturbance could be due to HSV-induced dysfunction of sweat glands. We developed a sweating disturbance-induced dry skin mouse model by infection with HSV-1.

2020 guidelines for the diagnosis and treatment of prurigo

Prurigo is a treatment-resistant skin disease characterized by multiple isolated papules/nodules that cause severe itch. Prurigo papules/nodules occur either as primary lesions or as secondary lesions due to persistent scratching. The fundamental concepts and classifications of prurigo have not been sufficiently established, and considerable confusion remains regarding this topic. Clinical guidelines for chronic prurigo in Japan were published in 2012 in an attempt to reduce confusion regarding the concepts of prurigo and to standardize laboratory tests and treatments. However, the diagnostic terms for prurigo and associated concepts have changed over time, and new forms of treatment are under development. We have, thus, updated and revised the guidelines to classify prurigo based on clinical forms and causes, and disease name classifications based on the clinical form have been further simplified, such as prurigo nodularis, prurigo chronica multiformis, and prurigo (not otherwise specified). Expressions for acute, subacute, and chronic forms are not used. These guidelines outline the current concepts and specify treatments for prurigo.

Prurigo nodularis as a sweat gland/duct-related disorder: resolution associated with restoration of sweating disturbance

Little attention has been given to the involvement of sweat glands/ducts in the pathogenesis of prurigo nodularis (PN). According to recent studies, PN is likely to develop under conditions characterized by dry skin, such as atopic dermatitis (AD), suggesting a strong impact of skin dryness on PN development. No therapeutic modalities produced complete resolution of PN without exacerbations. We previously reported that increases in skin dryness by sweating disturbance could initiate the development of AD. We investigated whether sweating responses were impaired in refractory PN lesions; and, if so, we asked whether the PN lesions could resolve by restoring sweating disturbance. Using the impression mold technique, which allows an accurate quantification of individual sweat gland/duct activity, we examined basal sweating under quiescent conditions and inducible sweating responses to thermal stimulus in PN lesions and normal-appearing skin in the same patients before and after treatment with a moisturizer or topical corticosteroids. Sweating disturbance, either basal or inducible, was most profoundly detected in the "hub" structure corresponding to the center of PN papule before the treatment. This sweating disturbance was immunohistochemically associated with the leakage of sweat into the dermis. This disturbance was restored by treatment with a moisturizer. Our limitations include a relatively small patient cohort and lack of blinding. Sweating disturbance could be one of the aggravating factors of PN development. Refractory PN with low skin hydration may resolve by restoring sweating disturbance.

Sweat is a most efficient natural moisturizer providing protective immunity at points of allergen entry

Although there is a growing acceptance that sweat could play a detrimental role in various allergic skin diseases, the possibility that sweat is also involved in maintenance of skin hydration and skin-specific immune responses has not been acknowledged. We initially describe physiological role of sweat in both maintaining skin hydration and thermoregulation. The purpose of this article is to provide the reader with objective evidence that sweating is intimately linked to vital stratum corneum barrier function and usefulness of application of moisturizers in clinical care of allergic skin diseases. This review also covers how sweating disturbance would leave the skin vulnerable to the development of various allergic skin diseases, such as atopic dermatitis. New therapeutic approaches would specifically target such sweating disturbance in these allergic skin diseases.