Immunohistochemical evaluation of keratins and involucrin in differentiating between palmoplantar pustulosis and pompholyx.

BACKGROUND: Palmoplantar pustulosis (PPP) and pompholyx are chronic diseases characterized by pustules and vesicles on the palms and soles. These disorders often have similar clinicopathological features, which lead to diagnostic difficulties. We aimed to investigate the expression patterns of keratins and involucrin in PPP and pompholyx using immunohistochemical staining. METHODS: Skin biopsies from patients with PPP (n = 40) and pompholyx (n = 22) were immunohistochemically analyzed for Keratin 5, 9, 14, and involucrin expression. RESULTS: K5 expression was higher in PPP than in pompholyx, with diffusely positive expression in the basal, spinous, and granular layers. K14 expression did not differ between groups. K9 expression was observed near the pompholyx vesicle (P = 0.014) and stratum spinosum (P < 0.001) but was almost absent around PPP pustules. Involucrin expression was diffused around the PPP pustules and partially around the pompholyx vesicles, but without statistical significance (P = 0.123). Involucrin expression was elevated in the basal layer of the PPP compared with that in the pompholyx (P = 0.023). CONCLUSION: PPP and pompholyx exhibited distinctive differentiation in the expression of K5, K9, and involucrin.

Spongiform pemphigoid: A case series of an uncommon histopathologic pattern.

INTRODUCTION: Bullous pemphigoid is an autoimmune bullous disease characterized by subepidermal separation. We encountered cases of bullous pemphigoid confirmed by direct immunofluorescence study but demonstrating spongiotic dermatitis without subepidermal clefting. Many of them occurred in volar sites, mimicking dyshidrotic dermatitis. METHODS: We retrospectively collected patients who were pathologically and/or immunopathologically diagnosed with bullous pemphigoid from 2002 to 2017. Patients who presented with prominent spongiosis without subepidermal clefting were included and compared with patients who were diagnosed with dyshidrotic dermatitis. RESULTS: A total of nine cases of spongiform pemphigoid out of 385 bullous pemphigoid patients (2.3%) were identified and compared with 15 patients with dyshidrotic dermatitis. Average age of spongiform pemphigoid patients (76 years) was much older than that of the control group (34 years). Microvesicles in the mid- to lower epidermis (P < 0.001), eosinophils exocytosis (P < 0.001), and eosinophils microabscess (P < 0.001) in both the epidermis and papillary dermis were more common in spongiform pemphigoid. CONCLUSION: Spongiform pemphigoid mimics spongiotic dermatitis may result in a pathological diagnostic pitfall. The presence of eosinophil microabscess and exocytosis in the epidermis and papillary dermis were important clues. Immunofluorescence studies should be conducted to confirm the diagnosis of bullous pemphigoid.

The key role of aquaporin 3 and aquaporin 10 in the pathogenesis of pompholyx.

Pompholyx remains a chronic skin affliction without a compelling pathophysiological explanation. The disease is characterized by the sudden onset of vesicles exclusively in the palms and soles which generally resolves. However, the disease may progress and the vesicles may expand and fuse; with chronicity there is deep fissuring. Multiple therapeutic approaches are available, but the disease is often resistant to conventional treatments. Currently, oral alitretinoin is used for patients with resistant chronic disease; however, this therapy is only approved for use in the UK, Europe and Canada. In this paper we wish to put forward a hypothesis: exposure to water and the subsequent steep osmotic gradient imbalance are key factors driving skin dehydration seen in pompholyx patients once the disease becomes chronic. The mechanistic explanation for the epidermal fissuring might lie in the over-expression across the mid and upper epidermis, including the stratum corneum, of two water/glycerol channel proteins aquaporin 3 and aquaporin 10, expressed in the keratinocytes of afflicted pompholyx patients. The over-expression of these two aquaporins may bridge the abundantly hydrated dermis and basal epidermis to the outer environment allowing cutaneous water and glycerol to flow outward. The beneficial effects reported in alitretinoin-treated patients with chronic hand eczemas may be due potential regulation of aquaporin 3 and aquaporin 10 by alitretinoin.

A comparison of inflammatory mediator expression between palmoplantar pustulosis and pompholyx.

BACKGROUND: Both palmoplantar pustulosis (PPP) and pompholyx are clinically characterized by acute eruptions of vesicles or pustules on the palms or soles. OBJECTIVES: This study aims to compare the expression of certain inflammatory mediator genes and proteins between patients with PPP and pompholyx using skin tissue samples. METHODS: Skin biopsies obtained from lesional skin from patients with PPP (n = 7) and pompholyx (n = 5) were analysed by quantitative RT-PCR to measure the mRNA levels of nine genes, including IL-4, IL-8, IL-9, IL-17, IL-22, IFN-γ, CCL-20, granzyme and perforin. For immunohistochemical analysis, 34 paraffin-embedded skin specimens (PPP, n = 22; pompholyx, n = 12) were stained with anti-IL-8, IL-17A, IL-22 and granzyme B antibodies. RESULTS: Of genes analysed, IL-8 and IL-17A mRNA expression levels were significantly higher in the PPP group than the pompholyx group (P = 0.012 in both), whereas the mRNA expression of granzyme B was significantly higher in pompholyx when compared with PPP (P = 0.004). Regarding the IL-17A immunohistochemical staining, tissue from the PPP lesions contained significantly more IL-17A(+) cells in both the epidermis and papillary dermis when compared with pompholyx (P < 0.001 and P = 0.019 respectively). Moreover, the intensity of the IL-8 immunoreactivity was also greater in the PPP skin lesions than the pompholyx tissue (P < 0.001). CONCLUSIONS: IL-8 and IL-17A, both are increased in PPP tissue, may represent important immunologic mediators that help to differentiate this clinical entity from pompholyx. This study may provide useful clues in distinguishing PPP from pompholyx, as well as helping to understand the pathogeneses of these two diseases.