Acquired idiopathic generalized anhidrosis: possible pathogenic role of mast cells

Transcriptome profiling of anhidrotic eccrine sweat glands reveals that olfactory receptors on eccrine sweat glands regulate perspiration in a ligand-dependent manner

Sweat maintains systemic homeostasis in humans. Although sweating disorders may cause multifaceted health problems, therapeutic options for sweat disorders have not yet been established. To gain new insight into the mechanism underlying the regulation of perspiration, we compared eccrine sweat gland transcriptomes from hidrotic and anhidrotic lesions from patients with anhidrosis and found out that olfactory receptors were expressed differentially in anhidrotic and hidrotic eccrine sweat glands. We then confirmed OR51A7 and OR51E2 expression in human eccrine sweat glands by in situ hybridization and immunohistochemistry. An alkaline phosphatase-TGFα shedding assay revealed that β-ionone activates G-proteins through OR51A7 or OR51E2. The effect of topically applied β-ionone on sweating was examined with the quantitative sudomotor axon reflex test, which showed that responses to β-ionone differed between sexes. Topical β-ionone attenuated female sweating and augmented male sweating. Taken together, this study suggests that olfactory receptors expressed in eccrine sweat glands may regulate sweating in response to odorous ligands on the basis of sex. These unexpected results indicate that olfactory receptors may modulate sweating and that olfactory receptor modulators may contribute to the management of sweat disorders.

Cholinergic Urticaria: Subtype Classification and Clinical Approach

Cholinergic urticaria (CholU) is a subtype of chronic inducible urticaria with a chief complaint of itching and/or stinging, painful papular wheals that develop simultaneously with sweating. This review specifically focuses on several subtypes of CholU and specifically investigates the relationship between CholU and anhidrosis. We review recent publications and update the evidence around CholU, including the epidemiology, clinical features, diagnostic approaches, physiopathology, subtype classification, and therapeutic approaches. Multiple mechanisms contribute in a complex manner to the development of CholU, including histamine, sweat allergy, cholinergic-related substances, poral occlusion, and hypohidrosis/anhidrosis. A new schematic of the currently known pathological conditions has been created. Specific methods for diagnosing CholU, a provocation test, and evaluation methods for disease severity/activity and disease burden of CholU are summarized. The characteristics of the diseases that should be differentiated from CholU and examination methods are also summarized. The primary finding of this review is that CholU should be categorized based on the etiology and clinical characteristics of each subtype to properly manage and treat the disease. This categorization leads to improvement of therapeutic resistance status of this disease. In particular, a sweating abnormality should be given more attention when examining patients with CholU. Because CholU is not a homogeneous disease, its subtype classification is important for selection of the most suitable therapeutic method. Further elucidation of the pathophysiology of each subtype is expected.

Prognosis after steroid pulse therapy and seasonal effect in acquired idiopathic generalized anhidrosis

Acquired idiopathic generalized anhidrosis is a rare disease with unknown etiology. Sudden loss of sweating function adversely affects young patients' quality of life. Although systemic corticosteroid therapy is the most frequently reported treatment for the disease, its effectiveness is controversial because of the risk of recurrence. To assist clinical decision-making regarding whether to use steroids, we investigated the treatment responsiveness and recurrence rates in patients undergoing steroid pulse therapy and explored factors affecting these rates. We retrospectively collected data of 124 patients who received steroid pulse therapy to calculate the rate of responsiveness to the therapy. We also conducted a time-to-event analysis in a cohort of 57 patients who responded to steroid pulse therapy to estimate the recurrence rate after the therapy. As a result, the response and recurrence rates were 73% and 48%, respectively. Recurrence occurred within 1 year in most patients. The overall effectiveness of steroid pulse therapy was estimated to be 57% considering the recurrence rate. A delay from onset to treatment and younger age appeared to be negative factors for effectiveness. Moreover, we found a significant seasonal effect on both treatment and recurrence: autumn was the worst season for acquired idiopathic generalized anhidrosis in Japan. Our study revealed that steroid pulse therapy can be expected to be effective in half of treated patients. We recommend starting the therapy promptly after the diagnosis; however, it is also worth considering the season for treatment planning.

Clear cell injury associated with reduced expression of carbonic anhydrase II in eccrine glands consistently occurs in patients with acquired idiopathic generalized anhidrosis

Acquired idiopathic generalized anhidrosis (AIGA) is characterized by anhidrosis/hypohidrosis without other autonomic and neurological dysfunctions. It has been believed that AIGA patients usually present no significant morphological alterations in the secretory portion of eccrine glands consisting of clear, dark and myoepithelial cells. However, we have recently revealed morphological damage of eccrine glands in AIGA patients by immunohistochemistry. Moreover, inhibitory side-effects against carbonic anhydrase II (CA II) by the antiepileptic reagent topiramate have been reported to cause heat intolerance mimicking AIGA. To determine the precise morphological changes and CA II expression in eccrine glands of AIGA patients, electron microscopic observation and immunohistochemistry were applied to skin of both anhidrotic (non-sweating) and normohidrotic (sweating-preserved) sites, taken from each patient clinically diagnosed with AIGA. We found consistent clear cell injury in eccrine glands in anhidrotic skin samples of AIGA patients. Electron micrographs demonstrated edematous, swollen and destructive damage in clear cells of eccrine glands from non-sweating areas of almost all AIGA patients. Immunohistochemically, clear cells showed reduced CA II expression that was heterogeneously distributed in non-sweating skin. Some areas showed almost complete loss of CA II expression in spite of preserved dark cells, and others showed mild or moderate loss of it. Selective destruction of clear cells resulting in heterogenous atrophy in AIGA patients may be important to elucidate its etiology.

Degranulation and shrinkage of dark cells in eccrine glands and elevated serum carcinoembryonic antigen in patients with acquired idiopathic generalized anhidrosis

BACKGROUND

Acquired idiopathic generalized anhidrosis (AIGA) is characterized by anhidrosis/hypohidrosis without other autonomic and neurological dysfunctions. Pathologically, AIGA is considered to usually present no significant morphological alterations in eccrine glands, the secretory portion which consists of clear cells, dark cells, and myoepithelial cells. AIGA patients recently have been reported to show high serum concentrations of carcinoembryonic antigen (CEA).

OBJECTIVE

Our aim is to reveal morphological abnormalities of dark cells and investigate their relationship with serum CEA.

METHODS

We performed comparative analysis of eccrine glands between sweat-preserved and non-sweating skin in four AIGA patients. Serum CEA concentrations in 22 cases with AIGA were measured with healthy volunteers. Furthermore, we semiquantitatively investigated dermcidin, FoxA1 and CEA expression in eccrine glands of 12 cases with AIGA and 5 cases with non-AIGA.

RESULTS

Marked degranulation and shrinkage of dark cells consistently occurred in AIGA. Furthermore, high serum CEA concentrations were found in 14 of 22 AIGA patients (over 60%), but serum CEA levels were not correlated with CEA expression in eccrine glands. Dermcidin expression in dark cells apparently decreased in AIGA patients, severely in those with high serum CEA and moderately in those with low serum CEA, while well-preserved expression was found in non-AIGA subjects.

CONCLUSION

Our study suggests morphological damage and molecular dysregulation of dark cells, leading to impairment of their functions in AIGA patients. Severely damaged dark cells correspond to high serum CEA. Accordingly, these pathological changes in eccrine dark cells may be involved in anhidrosis/hypohidrosis of AIGA.

Cholinergic urticaria: epidemiology, physiopathology, new categorization, and management

PURPOSE

The aim of this study was to review the evidence on the epidemiology, physiopathology, categorization, and management of cholinergic urticaria. We specifically focused on several subtypes of cholinergic urticaria and investigated the relationship between cholinergic urticaria and idiopathic anhidrosis.

METHODS

Using an integrative approach, we reviewed publications addressing the epidemiology, clinical features, diagnostic approach, physiopathology, subtype classification, and therapeutic approach to cholinergic urticaria.

RESULTS

Multiple mechanisms were found to contribute to the development of cholinergic urticaria. This disorder should be classified based on the pathogenesis and clinical characteristics of each subtype. Such a classification system would lead to better management of this resistant condition. In particular, sweating function should be given more attention when examining patients with cholinergic urticaria.

CONCLUSIONS

Because cholinergic urticaria is not a homogeneous disease, its subtype classification is essential for selection of the most suitable therapeutic method.

Acquired idiopathic anhidrosis: a diagnosis often missed

BACKGROUND

Acquired idiopathic anhidrosis (AIA) is an uncommon entity characterized by anhidrosis in the absence of any neurologic or sweat gland abnormalities.

OBJECTIVE

The aim of this study was to characterize the clinical profile in a cohort of patients diagnosed with AIA at a tertiary dermatologic center.

METHODS

We retrospectively evaluated cases seen during a 10-year period. Inclusion criteria included all cases of generalized or partial anhidrosis with no obvious causes, confirmed by provocative starch-iodine sweat test. Ectodermal dysplasias, poral dysfunction from chronic dermatoses, autonomic dysfunction, and drug-induced causes were excluded.

RESULTS

Fifteen Chinese patients were diagnosed with AIA, mostly healthy young men with no significant medical or drug history, with variable extent of body surface area involvement. Serum immunoglobulin E, a complete blood cell count, thyroid function test, and antinuclear antibody levels were unremarkable. Anhidrotic areas revealed normal eccrine appendages with mild perivascular and perieccrine lymphocytic infiltrate. There were no neurologic abnormalities.

LIMITATIONS

This was a retrospective study.

CONCLUSION

Our study shows that AIA seems to be a heterogeneous group with no major dysfunction other than anhidrosis. Proper recognition and evaluation is paramount, especially for at-risk populations, so that appropriate measures on the prevention of heat injuries can be instituted.

New concepts of hive formation in cholinergic urticaria

Patients with cholinergic urticaria (CU) show a number of small, short-lasting hives when their body core temperature increases, usually during sweating following exercise or bathing. The precise mechanism(s) of hive formation in CU has been unclear except for the involvement of acetylcholine. We recently reported that most CU patients show immediate-type skin responses to their own sweat, whereas the rest of CU patients have positive autologous serum skin tests (ASSTs). The former group produced satellite wheals following acetylcholine injection, whereas the latter group produced hives in conjunction with hair follicles. We propose two subtypes of CU: 1) a sweat-hypersensitivity type with strong hypersensitivity to autologous sweat, nonfollicular hives, development of satellite wheals, and lack of positive ASST; and 2) a follicular type with follicular hives and positive ASST, but no hypersensitivity to autologous sweat or satellite wheals. We discuss the mechanisms of hive formation in these subtypes.