Photochemotherapy (PUVA) in the treatment of urticaria pigmentosa

Eight patients received PUVA for mastocytosis. Five women had typical adult-onset urticaria pigmentosa, without evidence of systemic disease. Another woman had suspected hepatic involvement while the remaining female had early-onset familial urticaria pigmentosa with morphologically atypical mast cells. The only male patient had cirrhosis with hepatic deposits of mast cells in addition to polycythaemia rubra vera. In all patients, except the man with systemic disease, there was reduced pruritus and wealing and partial to almost complete fading of the macules. The manifestations of urticaria pigmentosa recurred after treatment was discontinued. In both lesional and uninvolved skin there was no significant change in either the mean mast cell counts or mast cell ultrastructure after an average of twenty-seven PUVA exposures. In addition, PUVA did not cause a significant alteration in the histamine content of the skin. The beneficial effect of PUVA in urticaria pigmentosa therefore does not appear to be directly related to a change in mast cell numbers or morphology, or to the histamine concentration in the skin. Urticaria pigmentosa usually presents as a generalized maculo-papular rash which urticates on rubbing (Darier's sign). Many patients are troubled only by the unsightliness of the rash while some complain of pruritus, wealing or flushing. These symptoms are attributed to the release of histamine by mast cells which characteristically occur in increased numbers in the dermis. Symptomatic treatment is often unrewarding, but favourable results have been claimed for cimetidine with or without Hi blockers (Hirschowitz & Groarke, 1979; O'Laughlin & Bredfeldt, 1980) and for oral disodium cromoglycate (Soter, Austen & Wasserman, 1979; Czarnetski & Behrendt, 1981). In 1978, Christophers and colleagues reported that photochemotherapy (PUVA) produced symptomatic relief in all of ten adult patients with typical urticaria pigmentosa. Similarly encouraging results were subsequently reported from other centres (Ortonne et al., 1980; Allevato, Donatti & Cordero, 1980; Granerus, Roupe & Swanbeck, 1981; Väätäinen, Hannuksela & Karvonen, 1981). In this study we examined the effects of PUVA in eight adult patients with urticaria pigmentosa. Although PUVA produced a moderately good clinical response in seven out of these eight patients (reduced pruritus, reduced wealing and faded macules) quantitative studies failed to reveal a consistent effect of PUVA on either the mast cell population density or the histamine concentration in both lesional and clinically uninvolved skin. The findings arc discussed in relation to existing information concerning the effect of ultraviolet radiation (U VR) on mast cells and other constituents of the skin.     

Mast cell density in psoriatic skin. The effect of PUVA and corticosteroid therapy

Summary Numbers and volume fractions of mast cells in nonlesional and chronic lesional skin of psoriatic patients were compared with those of normal control skin. Mast cell densities were similar in psoriatic nonlesional and normal control skin. The superficial dermis of lesional psoriatic skin contained more mast cells than either normal or nonlesional psoriatic skin. Neither PUVA nor corticosteroid treatment for 3–4 weeks significantly reduced mast cell numbers or volume fractions in lesional skin, although both treatments clinically and histologically markedly improved the lesions. The results indicate that the initiation of the healing process in psoriatic plaques is not correlated with the mast cell density. The remaining high mast cell density may be normalized later, or after a longer therapy.     

Histamine-containing mast cells and their relationship to NGFr-immunoreactive nerves in prurigo nodularis: a reappraisal

The mast cell, which is a histamine-containing cell, has been found to have far more functions in skin inflammation than hitherto understood. To investigate the appearance of mast cells in prurigo nodularis, histamine immunohistochemistry in combination with nerve growth factor receptor (NGFr) double-staining as well as electron microscopic studies were performed. The results revealed that the histamine-containing cell number was increased in the lesional dermis. The mast cell size was also increased and the shape had become more dendritic. They tended to contact the epidermis and even infiltrated into it. In the histamine and NGFr double-staining, both an increased histamine-containing mast cell number and an increased number of NGFr-immuno-reactive nerve fiber profiles were revealed in the upper dermis of the prurigo nodularis lesional skin. Mast cells were seen in close vicinity to NGFr-positive nerves and sometimes even seemingly to contact single nerve fibers. At the ultrastructural level, it is obvious that the mast cell bodies become larger, having more abundant cytoplasm and organelles (e.g. mitochondria), but comparatively fewer characteristic granules. Mast cells were often observed to sprout long dendrites, with or without granules. The cells were also frequently seen to contact other cell types, and a mast cell infiltration into the epidermis was also found. The statistical results of mast cell numbers showed a significant increase in prurigo nodularis lesional skin compared to the normal controls. The present results further indicate that mast cells, together with cutaneous nerve fibers, are actively involved in the pathogenesis of the disease.     

Phototherapy of urticaria pigmentosa: Clinical response and changes of cutaneous reactivity,histamine and chemotactic leukotrienes

Summary Ten patients with moderate to very severe urticaria pigmentosa were studied for the therapeutic effect of photochemotherapy (PUVA; six adults) and selective ultraviolet phototherapy (SUP; four adolescents). Despite a high mean PUVA dosage (138.6 ±63.4 J/cm²), only two patients had a very good response, while three had a good response and one had a fair response. On the reduction of the frequency of treatments, the symptoms gradually recurred, and several months after the discontinuation of therapy, the clinical status had reached the level prior to PUVA. The results with SUP were even less encouraging. A number of biophysical and biochemical parameters of the skin were studied in five patients before PUVA treatment, immediately after several months of PUVA treatment and again 5 months after the discontinuation of PUVA treatment. Weal and erythema reactions to intracutaneous skin tests remained unchanged after PUVA, while wealing with topically applied dimethylsulfoxide (DMSO) decreased. Transepidermal water loss was markedly reduced over DMSO weals. Histamine levels, which were elevated in lesional but not in normal skin, dropped with PUVA treatment, but after the discontinuation of treatment, they increased again in the lesions. On reverse-phase high-performance liquid chromatography, two main chemotactic factors, leukotriene B₄ and 5-HETE, were identified in lesional skin. Chemotactic activity was elevated in both lesional and uninvolved patient skin, reached normal levels at both sites after PUVA and maintained these low levels for several months after the discontinuation of treatment. Our data suggest that PUVA has reversible anti-inflammatory effects on human skin, because it increases epidermal-barrier function and decreases the synthesis of mediators of inflammation. These observations show the transitory therapeutic benefit of PUVA in patients with urticaria pigmentosa.     

Quantitative enzyme-histochemical analysis of tryptase- and chymase-containing mast cells in psoriatic skin

Summary Tryptase-containing mast cells have recently been found to be increased in the upper dermis of psoriatic lesions. In the present study, the distribution of chymaseand tryptase-containing mast cells was morphometrically analysed at different dermal levels of lesional and non-lesional psoriatic skin (12 patients) as well as normal human skin. Mast cell tryptase was identified enzyme-histochemically, using Z-Gly-Pro-Arg-MNA as the substrate. For demonstrating mast cell chymase, a simple and specific enzyme-histochemical staining method was developed, using Suc-Val-Pro-Phe-MNA as the substrate. All mast cells positive for chymase were also positive for tryptase and Giemsa stain. Although the number of tryptase-positive mast cells was slightly increased throughout the dermis of lesional psoriatic skin, this increase was most pronounced in the upper dermis immediately beneath, and in close contact with, the epidermis. In contrast, the number of chymase-positive mast cells was clearly decreased in the upper dermis of psoriatic lesions, but not in the deeper dermis, as compared with non-lesional psoriatic skin. In addition, all chymase-positive mast cells observed in the upper dermis were very weakly stained when compared with those in the deeper dermis. No differences were found between non-lesional psoriatic skin and normal skin in which the number of mast cells containing chymase was 72–73% of the number containing tryptase. The present results suggest that T mast cells particularly, containing tryptase but no chymase, proliferate in psoriatic lesions, and that the increase in tryptase activity and the decrease in chymase activitiy in the upper dermis may lead to an imbalance in the biochemical regulatory systems.     

Oral photochemotherapy in lichen planus (LP) and mycosis fungoides (MF): ultrastructural modifications of the infiltrating cells.

Six patients (5 with mycosis fungoides and 1 with lichen planus) treated with PUVA, were subjected to biopsy of lesional skin before and during oral photochemotherapy. Ultrastructurally, a reduction in the density of cellular infiltrate was observed in the superficial dermis. In the same areas, necrotic cellular changes were observed. PUVA therapy exercises its beneficial effect by direct destruction of these cells.     

Quantitation of tryptase- and chymase-containing mast cells in cutaneous lichen planus.

The distribution and density of tryptase- and chymase-positive mast cells in lesional and non-lesional cutaneous lichen planus (LP) was analysed. For this, enzyme-histochemical staining techniques and morphometrical measurements were applied. In non-lesional LP skin, chymase-positive cells (TC mast cells) showed a distribution similar to that found in both non-lesional psoriatic skin and in normal skin. Tryptase-positive cells (reflecting both T and TC mast cells), however, were increased in number in the upper dermis of non-lesional LP skin. In lesional LP skin, there were fewer chymase-positive cells in the upper dermis, whereas there were more tryptase-positive cells. In the upper dermis, no differences in the number of tryptase containing cells were detected between lesional and nonlesional LP skin. In lesions of LP and psoriasis, tryptase-positive mast cells are increased but differ in their distribution in the papillary dermis. In psoriatic lesions, tryptase-positive cells are frequently observed in epidermal contact, a feature very rarely seen in LP lesions. The present results suggest that the increased numbers of T mast cells in the upper dermis of nonlesional LP skin may be involved in initiating the LP lesion. It seems unlikely that mast cells could be responsible for the epidermal basal cell damage, though T mast cells do participate in the general inflammatory reaction.     

Histochemical and immunohistochemical study in melasma: evidence of damage in the basal membrane

The pathogenesis of melasma has not been clearly elucidated. Using Fontana Masson; diastase-resistant periodic acid-Schiff stains; and immunohistochemistry to stem cell factor (SCF), its receptor c-kit, anti-mast cell tryptase, and anti-collagen type IV antibody, we evaluated melasma lesions and compared them with perilesional skin and photoprotected skin. Samples were taken from lesional and photoprotected nonlesional skin in 24 patients. In other 24 patients, we took biopsies of lesional and perilesional skin. With Fontana Masson, we observed many pigmented basal cells protruding into the dermis of the melasma skin. Periodic acid-Schiff stain and anti-collagen type IV showed damage on the basal membrane in 95.5% and 83%, respectively, in melasma lesion. The immunoreactivity of SCF and the prevalence of mast cells were increased in the dermis of melasma compared with perilesional dermis. The expression of c-kit was significantly increased at lesional epidermis; a frequent protrusion of c-kit-positive basal cells into the dermis was evident in 70% versus that in 29% of perilesional skin. The expression of c-kit was increased at lesional dermis of melasma compared with perilesional skin. We found a low correlation between c-kit expression and prevalence of mast cells; these were increased in melasma skin. The results may suggest a role of SCF, c-kit, and mast cells in the pathogenesis of melasma. We were surprised by the unexpected evidence of damage to basal membrane (BM), which could facilitate the fall or the migration of active melanocytes and melanin into the dermis allowing the constant hyperpigmentation in melasma.     

Mast cell tryptase and chymase in developing and mature psoriatic lesions

The number and distribution of mast cells in nonlesional and lesional skin samples from 13 psoriatic patients were analyzed enzyme- and immunohistochemically. Mast cell tryptase was stained with the sensitive substrate Z-Gly-Pro-Arg-4-methoxy-2-naphthylamide, and chymase with Suc-Val-Pro-Phe-MNA and monoclonal B7 anti-chymase antibody. In addition, healthy-looking skin from 27 psoriatic patients was tape-stripped resulting in induction of the Köbner response in 9 patients. Sequential biopsies were taken before and after (7, 14 and 21 days) tape-stripping, and both tryptase and chymase were stained enzyme-histochemically. In nonlesional psoriatic skin, 70 ± 24% (mean ± SD) of the mast cells contained chymase enzyme activity, and 78 ± 18% chymase immunoreactivity. About 10% of the chymase-immunoreactive cells lacked chymase activity. In lesional psoriatic skin, tryptase-positive cells were increased in number throughout the dermis but especially beneath the epidermis. Chymase immunoreactivity paralleled the tryptase activity, whereas chymase activity was strongly diminished both in terms of mast cell numbers and in staining intensity in the papillary dermis. The apparent inactivation of chymase may be due to the action of the chymase inhibitors, ₁-antitrypsin and ₁-antichymotrypsin, localized immunohistochemically in mast cells of lesional and nonlesional psoriatic skin. In the developing psoriatic lesion, mast cells displaying chymase activity were already 27–38% decreased in number in the upper dermis on day 7 after tape-stripping, along with the first clinical signs of psoriasis. Earliest alterations in tryptase-positive cells were observed on day 14 as increased mast cell contacts with the epidermis combined with only a slight increase in mast cell numbers in the upper dermis. During the development of a psoriatic lesion, TC mast cells (tryptase⁺, chymase⁺) increase in number in the upper dermis, but chymase becomes inactive at an early stage. The abundant presence of active trypase but inactive chymase in the upper dermis may have a potential role in psoriasis since both of these enzymes can process several biologically active peptides and proteins.     

Photohardening of polymorphic light eruption patients decreases baseline epidermal Langerhans cell density while increasing mast cell numbers in the papillary dermis

The pathogenesis of polymorphic light eruption (PLE) has been linked to a lack of UV‐induced immune suppression. To determine the role of Langerhans cells (LC), mast cells and regulatory T cells, biopsies from PLE patients were taken from exposed sites in spring before and after photohardening with 311 nm or PUVA as well as again in summer. Skin sections were assessed for the presence of Langerin/CD1a+ LC and CD3+, CD4+, CD25+ or FoxP3+ T cells and mast cells. Photohardening transiently decreased the density of epidermal LC and significantly increased a low baseline mast cell density in the papillary dermis of PLE patients. Baseline T cell numbers in the skin were low, and there was no difference in PLE patients among any time point. This suggests that LC suppression together with recruitment of mast cells into photohardened skin may be a key cellular event underlying the mechanism by which phototherapy protects from PLE.     

Dermal mast cells in mastocytosis: fixation, distribution and quantitation

The mast cell distribution and number were studied in skin biopsies of 18 mastocytosis patients and 10 controls. The biopsies were stained for mast cells with toluidine blue at pH 0.5. The number in the upper dermis of lesional abdominal skin was at least twice as high as that of normal adjacent skin. Fixation in iso-osmotic 0.6% formaldehyde and 0.5% acetic acid, revealed more mast cells than conventional 4% formaldehyde fixation. Staining for 5 days, when compared to the normal for 30 min, increased the number of demonstrable mast cells just as did the change in fixation. Conventional formaldehyde fixation thus partially blocks the dye-binding of cutaneous mast cells, about 20% of the cells escaping detection. The degree of aldehyde blocking was similar in lesional and normal skin. A more pronounced blocking of dye-binding has been demonstrated previously in gut mucosal mast cells. Whether the blocking of dye-binding is an expression of heterogeneity in dermal mast cells remains to be determined.     

Microdialysis of histamine in the skin of patients with mastocytosis

Mastocytosis represents a group of disorders characterized by the proliferation and accumulation of mast cells in tissue. The aim of the present study was to examine whether the interstitial histamine concentration in the skin is increased in mastocytosis patients and whether it correlates with the number of mast cells, the amount of metabolite N-methyl-imidazole acetic acid in the urine and the tryptase in serum. In 7 mastocytosis patients on a standardized diet, the analysis of histamine was performed on microdialysates obtained from catheters positioned intracutaneously in involved and uninvolved skin. N-methyl-imidazole acetic acid in the urine was collected for 24 h. Biopsies for analyses of mast cells were taken from skin adjacent to the microdialysis catheters. The histamine concentrations were 42+/-14, 12+/-3 (P<0.05) and 8+/-2 nmol/l (mean+/-SEM, n=7) in skin eruptions, non-lesional skin and plasma respectively. Mean N-methyl-imidazole acetic acid in the urine (9.7+/-3.5 mmol/mol creatinine) and mean tryptase (124+/-54 microg/l) had increased in all patients. In the present study, no linear correlation was found between these parameters and interstitial histamine in lesional skin. This finding corresponds to the fact that the concentration of histamine metabolites and tryptase derives from the entire mast-cell population, while interstitial histamine in the dermis represents the local tissue concentration before metabolic transformation. The microdialysis of histamine in the skin of mastocytosis patients could be used as a tool to investigate the effects of dermal mast-cell histamine release in different kinds of treatment regimen.     

Increased mast cell expression of PAR‐2 in skin inflammatory diseases and release of IL‐8 upon PAR‐2 activation

Please cite this paper as: Increased mast cell expression of PAR‐2 in skin inflammatory diseases and release of IL‐8 upon PAR‐2 activation. Experimental Dermatology 2010; 19: 117–122. Abstract: Mast cells are increasingly present in the lesional skin of chronic skin inflammatory diseases including psoriasis and basal cell carcinoma (BCC). It has previously been shown that proteinase‐activated receptor (PAR)‐2 is expressed by mast cells, and tryptase is a potent activator of this receptor. In this study, skin biopsies from both healthy‐looking and lesional skin of patients with psoriasis and superficial spreading BCC were collected and the expression of PAR‐2 immunoreactivity in tryptase‐positive mast cells was analysed. PAR‐2 expression was confirmed in vitro in different mast cell populations. Cord‐blood derived mast cells (CBMC) were stimulated with a PAR‐2 activating peptide, 2‐furoyl‐LIGRLO‐NH₂. Consequently, IL‐8 and histamine production was analysed in the supernatants. We observed a significant increase in the percentage of mast cells expressing PAR‐2 in the lesional skin of psoriasis and BCC patients compared with the healthy‐looking skin. HMC‐1.2, LAD‐2 and CBMC mast cells all expressed PAR‐2 both intracellularly and on the cell surface. CBMC activation with the PAR‐2 activating peptide resulted in an increased secretion of IL‐8, but no histamine release was observed. Furthermore, both PAR‐2 and IL‐8 were co‐localized to the same tryptase‐positive mast cells in the lesional BCC skin. These results show that mast cells express increased levels of PAR‐2 in chronic skin inflammation. Also, mast cells can be activated by a PAR‐2 agonist to secrete IL‐8, a chemokine which can contribute to the progress of inflammation.     

Quantitative analysis of tryptase- and chymase-containing mast cells in atopic dermatitis and nummular eczema

The distribution of mast cells (MCs) containing tryptase (T) and chymase (C) was studied in the non-lesional and lesional skin of 26 patients with atopic dertnatitis (AD) and 23 patients with non-atopic nummular eczema (NE). and in the skin of eight healthy controls. T and C activities were demonstrated enzymehistochemically using 2-Gly-Pro-Arg-MNA and Suc-Val-Pro-Phe-MNA as substrates, respectively. The T- and C-containing MCs were counted separately in the epidermis, in contact with the basement membrane. In the papillary dermis and in different dermal levels (0·2 mm each). Also, the C protein was determined immunohistochemically. T-positive MCs were similarly distributed in non-lesional and lesional skin of both AD and NE. The MC number was relatively high in the upper dermis (papillary dermis and levels I and I!) of non-lesional and lesional skin of AD. In the upper dermis of non-lesional AD and NE skin and in normal skin, about 50% of T-positive MCs displayed C activity, whereas the percentage in lesional AD and NE skin was only about 30%. hi this respect, the non-lesional and lesional samples differed significantly froLu each other in both dennatoses (in AD p = 0%005, in NEP = 0·002. Students' t-test). In all samples the MC number decreased in the deeper dermal levels, although numerous T-containing MCs were still counted in the deeper dermis (dermal levels IV-VII) of lesional AD and NE skiti. differing significantly from the MC number in normal skin (In ADp = 0·005. in NE p=0·041). In the deeper dermis. the percentage of MCs containing active C was about 70% in non-lesional and lesional AD and NE. and about 90% in normal healthy skin. However, in the upper dermis of non-lesional and lesional skin of both AD and NE. about H()% of all MCs contained the C protein, which differed significantly from the value of 100% in normal skin (p<0·5). In conclusion, the increased number of T-positive MCs in the upper dermis of non-lesional and lesional AD contributes to promoting inflammation. C apparently loses its activity in the upper dermis of lesional AD and especially in NE. Thus. Ihe enzyme partially lacks its capability to suppress inflammation, such as degradation of neuropeptides and proteins. The dysregulation of these proteinases exists already in non-lesional skin of AD and NE.     

Mast cells are one major source of interleukin-4 in atopic dermatitis

Several reports have shown the presence of T-helper lymphocytes with Th2 characteristics in the skin lesions of atopic dermatitis (AD). However. Th2 cells themselves require an exogenous pulse of IL-4 to initiate their differentiation and synthesis of IL-4. As mast cells have recently been shown to contain IL-4, this finding prompted us to investigate IL-4 in mast cells of AD lesions, to determine if they might provide the IL-4 pulse needed by the Th2 cells. In this study, we measured IL-4 immunoreactivity in mast cells of non-lesional and lesional skin sections from 20 patients with AD. Ten patients with nummular eczema (NE) without any atopic features or background, and five healthy subjects, served as the control groups. Mast cells were first identified using an enzyme-histochemical staining method for tryptase. Subsequently, the sections were photographed, the tryptase stain was removed, and IL-4 was demonstrated with a polyclonal antibody. The sections were photographed again, and the percentage of IL-4-positive mast cells was calculated. The percentage of mast cells exhibiting IL-4 immunoreactivity in the upper dermis in lesional vs, non-lesional skin was 66±18% vs. 37±18% in AD (P<0.0001, paired t-test), but only 46±19% vs. 31±22% in NE. In the skin of healthy controls, only 23±25% of the mast cells were positive for IL-4. In addition, a significant difference was found between lesional skin of AD vs. NE patients (P<0.008, unpaired t-test). Moreover, the staining intensity of IL-4 in mast cells was clearly increased in the lesional compared with the non-lesional AD skin. Mast cells appeared to be the main cell type containing IL-4 in 40% of the lesional AD skin specimens, whereas in the remaining 60% prominent IL-4-positive mononuclear cell infiltrates were also present. In the non-lesional skin, mast cells appeared to be the main cell type containing IL-4 in all specimens. These results indicate that mast cells are one major source of IL-4 in lesional and non-lesional AD skin, and they could contribute significantly to the development of AD.     

The effect of 8-methoxypsoralen plus long-wave ultraviolet (PUVA) radiation on mast cells: PUVA suppresses degranulation of mouse skin mast cells induced by compound 48/80 or concanavalin A

In order to see whether 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet (UVA) radiation (PUVA) has an influence on immediate-type skin reactions, we have undertaken an animal study. Ears of mice were treated with a 0.5% 8-MOP solution topically plus UVA radiation (1.5-2.5 J/cm2). After PUVA radiation, skin responses to intradermal injection with mast cell liberators, including compound 48/80 (2.5 mg/ml, 10 microliter) and concanavalin A (Con-A) (2.0 mg/ml), or with a mixture of 5-hydroxytryptamine (5-HT) and histamine as vasodilator (1.0 mg/ml and 50 mM, respectively) were examined with time (2 h-14 days). At each time point, an ear swelling response (ESR) was measured with a dial thickness gauge. The rate of mast cell degranulation and mast cell numbers were assessed by light microscopy using toluidine blue-stained semithin (1 micron) sections. ESR induced by compound 48/80 or Con-A was significantly suppressed dose-dependently (greater than 42% inhibition) by PUVA between 2 h-3 days postirradiation as compared with that in nonirradiated control mice, and the value returned to normal levels by 7-14 days. Compound 48/80- or Con-A-induced mast cell degranulation (%) was remarkably decreased between 2 h-3 days (greater than 48% inhibition) in accordance with the suppression in ESR and it was restored to the rates in nonirradiated controls by 7-14 days. Neither ESR nor percent degranulation was affected by UVA radiation only (less than 3.5 J/cm2) or application of 8-MOP only. 5-HT plus histamine-mediated ESR was not altered at all by PUVA throughout the experimental period. Since PUVA radiation itself at given doses did not produce measurable ESR, mast cell degranulation, or a reduction in mast cell numbers, and since PUVA did not affect a normal vascular response to vasodilator, it seemed that decreased skin reactivity to mast cell degranulators by PUVA might be due to a PUVA-induced noncytolytic alteration in mast cell release mechanisms.     

Quantitative analysis of contact sites between mast cells and sensory nerves in cutaneous psoriasis and lichen planus based on a histochemical double staining technique

Summary The aim of the present study was to test further our previous hypothesis that the inflammatory reaction in psoriasis is neurogenic. For this purpose, contact sites between mast cells and sensory nerves were morphometrically analysed in the basement membrane zone, papillary dermis and three dermal zones of lesional/non-lesional psoriatic and lichen planus skin as well as in healthy control skin. The analyses were made on sections stained with a histochemical double stain developed for this study. With the double stain, active mast cell tryptase was stained blue enzyme histochemically, and the sensory nerves black using specific monoclonal anti-neurofilament antibodies with immunogold. In psoriatic lesions, both mast cells and mast cell — nerve contacts were markedly more frequent in the basement membrane zone and in the papillary dermis when compared with the corresponding areas in the other groups. Mast cell numbers were increased in both lesional and symptom-free skin in lichen planus, but no increase was found in the mast cell — nerve contacts. Increased contacts between mast cells and sensory nerves indicate that the elements exist for neurogenic inflammation in psoriatic lesions. These increased contacts are not due to the extensive inflammatory reaction only, because they were not observed in lichen planus lesions.     

In vitro functional reactivities of cutaneous mast cells from patients with mastocytosis

Cutaneous mast cells from 3 patients with mastocytosis were evaluated for their morphologic characteristics and in vitro functional reactivities to different secretory agonists. By electron microscopy, mastocytosis mast cells appeared larger than normal skin mast cells, frequently had atypical, highly indented or bilobed nuclei, and each contained numerous, elongated cytoplasmic projections. Suspensions of mastocytosis mast cells were obtained from lesional skin biopsy specimens, and their response to both immunologic and nonimmunologic secretagogues was compared with mast cells from normal skin. Lesional skin mast cells had a net histamine release of 12.3% (+/- 1.3 SEM) and 31.1% (+/- 6.0 SEM) following stimulation with the purified human anaphylotoxin C3a and mouse monoclonal antihuman IgE antibodies, respectively. This specific release was similar to the responses observed in normal skin mast cells (11.5% +/- 4.5 SEM and 16.7% +/- 2.1 SEM, respectively). Mast cells from cutaneous lesions of mastocytosis also responded to the nonimmunologic secretagogues, morphine sulfate and calcium ionophore A23187 with a specific histamine release of 15.1% (+/- 1.2 SEM) and 39.8% (+/- 8.7 SEM), respectively. The results of this study demonstrate that mast cells from lesions of mastocytosis are morphologically atypical, but have a histamine content similar to normal skin mast cells and retain their functional reactivities to clinically relevant secretory stimuli.     

Acral lesions of vitiligo: why are they resistant to photochemotherapy?

Background Acral lesions of vitiligo are usually resistant to conventional lines of treatment as well as surgical interventions. Objective To clarify causes underlying resistance of acral lesions to pigmentation in vitiligo by studying some of the factors associated with mechanisms of repigmentation following photochemotherapy. Methods The study included twenty patients with active vitiligo. Skin biopsies were taken from lesional and perilesional skin of areas expected to respond (trunk and proximal limb) and skin of acral areas, before and after PUVA therapy. Sections were stained with H and E, Melan‐A, MHCII, CD1a, SCF and c‐kit protein. Results Before treatment acral areas showed significantly lower hair follicle density, melanocyte density, Langerhans cell (LC) density, epidermal MHCII expression, lesional SCF expression and perilesional c‐kit expression. Following treatment with PUVA in both non‐responsive acral and repigmenting non‐acral lesions identical immunohistochemical changes in the form of significant decrease in LC density, epidermal MHC‐II and SCF expression were observed. Conclusion The surprisingly similar histochemical changes in response to PUVA in acral and non‐acral lesions did not manifest with clinical repigmentation except in non‐acral ones. Factors such as inherent lower melanocyte density, lower melanocyte stem cell reservoirs and/or lower baseline epidermal stem cell factor may be considered as possible play makers in this respect.     

Suction blister fluid histamine in fixed drug eruption.

The histamine concentration was measured from suction blister fluid obtained from normal and lesional skin of 8 patients with fixed drug eruption (FDE) caused by phenazone salicylate and from that of 2 healthy control subjects. In blister fluid samples obtained before peroral challenge with phenazone salicylate, the histamine concentrations were below 5 nmol/l both in uninvolved skin and in sites of previous FDE lesion (sample 0). After challenge, samples were taken from the incipient reaction that was visible after an average of 155 min. Histamine levels were significantly elevated in the blister fluid of 2 out of 8 FDE lesions (200 and 640 nmol/l) but in none of the uninvolved skin (sample 1). Two hours later (sample 2) the histamine levels were elevated in both uninvolved (mean 51.4 nmol/l) and lesional skin (mean 168 nmol/l). After 24 h (sample 3) the corresponding mean value was 25.4 nmol/l for uninvolved skin and 108 nmol/l for lesional skin. The histamine values in the blister fluid from FDE lesions in samples 2 and 3 were significantly higher (p less than 0.05) than those in the control blisters of uninvolved skin. An elevation of histamine levels comparable to that in the uninvolved skin of FDE patients was seen in the 2 healthy control subjects studied. The present study provides direct evidence of early release of histamine from mast cells or basophils in FDE and suggests that histamine is one of the mediators of clinical symptoms of FDE.