The absence of apoeccrine glands in the human axilla has disease pathogenetic implications, including axillary hyperhidrosis

Hyperhidrosis: A Central Nervous Dysfunction of Sweat Secretion

Hyperhidrosis (HH) is a central nervous dysfunction characterized by abnormally increased sweating due to a central dysregulation of sweat secretion. HH significantly affects the quality of life of patients in their private, social and professional environments. Physiologically, sweating is a mechanism that regulates body temperature, but it may also be triggered by emotional or gustatory stimuli. There are two main types of sweat glands: eccrine and apocrine glands. The central nervous system controls sweat secretion through the release of neurotransmitters into the autonomous nervous system (ANS) that activate the sweat glands. The hypothalamus has two separate neuronal pathways, one for thermoregulation and one for emotions. HH may thus be due to either a neuronal dysfunction of ANS regulation leading to a hyperactivity of the sympathetic nervous system, or to abnormal central processing of emotions. Crucially, there is no dysfunction of the sweat glands themselves. Various pathogenic mechanisms have been proposed to be involved in pathological sweat secretion in HH, ranging from structural changes within the ANS to increased expression of aquaporin 5 and upregulation of activin A receptor type 1 in eccrine sweat glands. Although a genetic predisposition has been demonstrated, it remains unclear exactly which genes are involved. To identify new, potential therapeutic targets and to improve treatment options, a good understanding of the signaling pathways involved, the underlying mechanisms, and the genetic components is essential. In this review we discuss the various aspects of sweat physiology and function that are necessary to explain pathological sweating. Our aim is to raise awareness of the complexity of HH to promote a better understanding of the disorder.

Differential antigen expression between human apocrine sweat glands and eccrine sweat glands

Bromhidrosis has a great negative impact on personal occupation and social psychology. It is not yet clear whether bromhidrosis is caused by apocrine sweat glands or the co-action of apocrine sweat glands and eccrine sweat glands. To distinguish between apocrine sweat glands and eccrine sweat glands, specific antigen markers for apocrine sweat glands and eccrine sweat glands must be found first. In the study, we detected the expression of K7, K18, K19, Na+-K+-2Cl- cotransporter 1 (NKCC1), carbonic anhydrase II (CAII), Forkhead transcription factor a1 (Foxa1), homeobox transcription factor engrailed homeobox1 (En1), gross cystic disease fluid protein-15 (GCDFP-15), mucin-1 (MUC-1), cluster of differentiation 15 (CD15) and apolipoprotein (APOD) in eccrine sweat glands and apocrine sweat glands by immunofluorescence staining. The results showed that K7, K18, K19, Foxa1, GCDFP-15 and MUC-1 were expressed in both apocrine and eccrine sweat glands, CD15 and APOD were only expressed in apocrine sweat glands, and CAII, NKCC1 and En1 were only expressed in eccrine sweat glands. We conclude that CD15 and APOD can serve as specific markers for apocrine sweat glands, while CAII, NKCC1 and En1 can serve as specific markers for eccrine sweat glands to differentiate the two sweat glands.

A Phase 3, Randomized, Multi-center Clinical Trial to Evaluate the Efficacy and Safety of Neu-BoNT/A in Treatment of Primary Axillary Hyperhidrosis

BACKGROUND

Botulinum toxin type A is widely used to treat primary axillary hyperhidrosis and has proven to be an effective and safe approach. Onabotulinumtoxin A was approved by the FDA as a treatment for primary axillary hyperhidrosis. This study aimed to evaluate the efficacy and safety of Neu-BoNT/A in subjects diagnosed with primary axillary hyperhidrosis.

METHODS

The Hyperhidrosis Disease Severity Scale, gravimetric measurement of sweat, and Global Assessment Scale were analyzed at weeks 4, 8, 12, and 16 to determine the effect of treatment. Adverse events, physical examination, and vital signs were monitored.

RESULTS

Subjects treated with Neu-BoNT/A showed statistically significant improvement by all 3 methods at weeks 4, 8, 12, and 16 (P value = 0.00). There were no severe adverse events or significant changes in vital signs, physical examination, or laboratory tests.

CONCLUSION

Neu-BoNT/A can be effectively and safely used for primary axillary hyperhidrosis.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

SLIDE-Novel Approach to Apocrine Sweat Sampling for Lipid Profiling in Healthy Individuals

We designed a concept of 3D-printed attachment with porous glass filter disks—SLIDE (Sweat sampLIng DevicE) for easy sampling of apocrine sweat. By applying advanced mass spectrometry coupled with the liquid chromatography technique, the complex lipid profiles were measured to evaluate the reproducibility and robustness of this novel approach. Moreover, our in-depth statistical evaluation of the data provided an insight into the potential use of apocrine sweat as a novel and diagnostically relevant biofluid for clinical analyses. Data transformation using probabilistic quotient normalization (PQN) significantly improved the analytical characteristics and overcame the ‘sample dilution issue’ of the sampling. The lipidomic content of apocrine sweat from healthy subjects was described in terms of identification and quantitation. A total of 240 lipids across 15 classes were identified. The lipid concentrations varied from 10⁻¹⁰ to 10⁻⁴ mol/L. The most numerous class of lipids were ceramides (n = 61), while the free fatty acids were the most abundant ones (average concentrations of 10⁻⁵ mol/L). The main advantages of apocrine sweat microsampling include: (a) the non-invasiveness of the procedure and (b) the unique feature of apocrine sweat, reflecting metabolome and lipidome of the intracellular space and plasmatic membranes. The SLIDE application as a sampling technique of apocrine sweat brings a promising alternative, including various possibilities in modern clinical practice.

Treatment of axillary bromhidrosis in adolescents by combining electrocauterization with ultrasound-guided botulinum toxin type A injection

The aim of this study is to investigate the efficacy of treatment-combined electrocauterization after removal of apocrine sweat glands with ultrasound-guided (BOTOX) injection for adolescents with axillary bromhidrosis. From January 2015 to January 2018, 90 adolescents with axillary bromhidrosis were recruited and randomly divided into three groups (group A, B, and C). Patients in group A underwent electrocauterization after removal of apocrine sweat glands, patients in group B received ultrasound-guided BOTOX injection, and patients in group C had electrocauterization after the removal of apocrine sweat glands followed by ultrasound-guided BOTOX administration after two weeks. All patients were followed up for one year. The percentages of axillary malodor score at twelve months after treatments compared with pre-operation for group A, group B, and group C were 20.2%, 27.5%, and 12.5%, respectively. Significant statistical differences were observed in changes of axillary malodor score among the three groups at three, six, nine and twelve months postoperatively. Satisfaction rates of group A, group B, and group C were 90.0%, 93.3%, and 96.7%, respectively. The side effects after surgery in group A were similar to group C, and no side effect was observed in group B. One-year postoperative scar formation rate of group A was 16.7%, which was significantly higher than that of group B (0) and group C (6.66%). Combination of electrocauterization after removal of apocrine sweat glands with ultrasound-guided BOTOX injection showed better treatment effects.

Neural control of sweat secretion: a review

BACKGROUND

Humans have 4 million exocrine sweat glands, which can be classified into two types: eccrine and apocrine glands. Sweat secretion, a constitutive feature, is directly involved in thermoregulation and metabolism, and is regulated by both the central nervous system (CNS) and autonomic nervous system (ANS).

OBJECTIVES

To explore how sweat secretion is controlled by both the CNS and the ANS and the mechanisms behind the neural control of sweat secretion.

METHODS

We conducted a literature search on PubMed for reports in English from 1 January 1950 to 31 December 2016.

RESULTS AND CONCLUSIONS

Acetylcholine acts as a potent stimulator for sweat secretion, which is released by sympathetic nerves. β-adrenoceptors are found in adipocytes as well as apocrine glands, and these receptors may mediate lipid secretion from apocrine glands for sweat secretion. The activation of β-adrenoceptors could increase sweat secretion through opening of Ca²⁺ channels to elevate intracellular Ca²⁺ concentration. Ca²⁺ and cyclic adenosine monophosphate play a part in the secretion of lipids and proteins from apocrine glands for sweat secretion. The translocation of aquaporin 5 plays an important role in sweat secretion from eccrine glands. Dysfunction of the ANS, especially the sympathetic nervous system, may cause sweating disorders, such as hypohidrosis and hyperhidrosis.

Reference values for skin microanatomy: A systematic review and meta-analysis of ex vivo studies

BACKGROUND

Few studies have characterized reference values of normal human skin microanatomy parameters.

OBJECTIVE

To quantify histologic measurements of epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density as a function of age and anatomic site.

METHOD

We searched the PubMed, Embase, Web of Science, and Cochrane databases for articles published through May 25, 2017. Two reviewers independently screened 2016 articles; 327 relevant articles and 151 additional articles found via forward or reference citations underwent full-text review by 1 of 4 reviewers for relevance, data extraction, and critical appraisal. Weighted averages, meta-analysis, and meta-regression were used in statistical analysis.

RESULTS

A total of 56 articles were included; when all anatomic locations were used, the overall estimates for epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density were 99.75 μm (95% confidence interval [CI], 83.25-116.25), 955.05 cells/mm² (95% CI. 880.89-1029.21), 1.40 hairs/mm² (95% CI. 0.91-1.89), and 1.28 glands/mm² (95% CI. 0.91-1.64), respectively.

LIMITATIONS

There was significant data heterogeneity across studies, possibly because of differences in histological techniques and absence of standardized microanatomy definitions.

CONCLUSIONS

We established summary estimates for normal human skin microanatomy parameters.

The secretory clear cell of the eccrine sweat gland as the probable source of excess sweat production in hyperhidrosis

Primary hyperhidrosis is characterized by excessive sweating in palmar, plantar and axillary body regions. Gland hypertrophy and the existence of a third type of sweat gland, the apoeccrine gland, with high fluid transporting capabilities have been suggested as possible causes. This study investigated whether sweat glands were hypertrophied in axillary hyperhidrotic patients and if mechanisms associated with fluid transport were found in all types of axillary sweat glands. The occurrence of apoeccrine sweat glands was also investigated. Axillary skin biopsies from control and hyperhidrosis patients were examined using immunohistochemistry, image analysis and immunofluorescence microscopy. Results showed that glands were not hypertrophied and that only the clear cells in the eccrine glands expressed proteins associated with fluid transport. There was no evidence of the presence of apoeccrine glands in the tissues investigated. Preliminary findings suggest the eccrine gland secretory clear cell as the main source of fluid transport in hyperhidrosis.

Primary focal hyperhidrosis: current treatment options and a step-by-step approach

Primary focal hyperhidrosis is a common disorder for which treatment is often a therapeutic challenge. A systematic review of current literature on the various treatment modalities for primary focal hyperhidrosis was performed and a step-by-step approach for the different types of primary focal hyperhidrosis (axillary, palmar, plantar and craniofacial) was established. Non-surgical treatments (aluminium salts, local and systemic anticholinergics, botulinum toxin A (BTX-A) injections and iontophoresis) are adequately supported by the current literature. More invasive surgical procedures (suction curettage and sympathetic denervation) have also been extensively investigated, and can offer a more definitive solution for cases of hyperhidrosis that are unresponsive to non-surgical treatments. There is no consensus on specific techniques for sympathetic denervation, and this issue should be further examined by meta-analysis. There are numerous treatment options available to improve the quality of life (QOL) of the hyperhidrosis patient. In practice, however, the challenge for the dermatologist remains to evaluate the severity of hyperhidrosis to achieve the best therapeutic outcome, this can be done most effectively using the Hyperhidrosis Disease Severity Scale (HDSS).

Dilation of apocrine glands. A forgotten but helpful histopathological clue to the diagnosis of axillary Fox-Fordyce disease

Fox-Fordyce disease is a condition with protean histopathological alterations whose pathogenesis remains a mystery. Although recent studies have addressed histological changes specific of this disease, including perifollicular xanthomatosis, no attention has been given to apocrine acini dilation as an adjunct histopathological finding to the diagnosis. Moreover, although previous efforts were done to demonstrate that perifollicular foamy histiocytes harbor apocrine secretion content, this concept has not been proved to date. In this study, we report 2 cases harboring prominent dilation of apocrine coils with mucinous content. Such mucinous content showed mucin profile identical to the dermal mucin deposits in both cases. Of note, perifollicular foamy histiocytes demonstrated cytoplasmic mucin, supporting the suggestion that these cells phagocytose apocrine secretion. Although not specific, apocrine coil dilation is another histopathological feature of Fox-Fordyce disease and it may be used as a low-power magnification clue for the correct diagnosis. We also propose that the so-called perifollicular xanthomatosis may be composed of muciphages or mixed cell (muciphages/xanthomatous) population, an issue that should be further investigated in future studies.

[Novel adverse effects of laser-assisted axillary hair removal]

BACKGROUND

Several adverse effects of depilatory laser may now be commonly expected in relation to skin type and anatomic location. We report and analyse unusual events in patients undergoing laser-assisted axillary hair removal, including hyperhidrosis, bromhidrosis and leukotrichia.

OBJECTIVE

The aim of this study was to examine a large patient population, assess the frequency of these adverse effects, and establish a correlation with different hair-removal laser protocols.

PATIENTS AND METHODS

A retrospective case-control study of patients undergoing laser-assisted axillary hair removal was conducted to determine the incidence of these adverse effects in relation to skin type and types of laser used.

RESULTS

Hyperhidrosis, bromhidrosis and leukotrichia were seen in 11, 4, and 2% of patients respectively. Hyperhidrosis was significantly less frequent in patients with skin types III and IV than in those with skin type II or V. Combined diode and alexandrite laser sessions were associated with a significantly higher incidence of hyperhidrosis compared to diode or alexandrite sessions alone. Regarding bromhidrosis and leukotrichia, no significant correlation with age, skin type or laser settings was revealed by the statistical analysis.

CONCLUSION

Hyperhidrosis, bromhidrosis and leukotrichia are likely new adverse effects of laser-assisted axillary hair removal.