M. Picardo

Revised classification/nomenclature of vitiligo and related issues: the Vitiligo Global Issues Consensus Conference

During the 2011 International Pigment Cell Conference (IPCC), the Vitiligo European Taskforce (VETF) convened a consensus conference on issues of global importance for vitiligo clinical research. As suggested by an international panel of experts, the conference focused on four topics: classification and nomenclature; definition of stable disease; definition of Koebner’s phenomenon (KP); and ‘autoimmune vitiligo’. These topics were discussed in seven working groups representing different geographical regions. A consensus emerged that segmental vitiligo be classified separately from all other forms of vitiligo and that the term ‘vitiligo’ be used as an umbrella term for all non‐segmental forms of vitiligo, including ‘mixed vitiligo’ in which segmental and non‐segmental vitiligo are combined and which is considered a subgroup of vitiligo. Further, the conference recommends that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the disease as the latter is difficult to define precisely and reliably. The conference also endorsed the classification of KP for vitiligo as proposed by the VETF (history based, clinical observation based, or experimentally induced). Lastly, the conference agreed that ‘autoimmune vitiligo’ should not be used as a separate classification as published evidence indicates that the pathophysiology of all forms of vitiligo likely involves autoimmune or inflammatory mechanisms.

Guidelines for the management of vitiligo: the European Dermatology Forum consensus.

The aetiopathogenic mechanisms of vitiligo are still poorly understood, and this has held back progress in diagnosis and treatment. Up until now, treatment guidelines have existed at national levels, but no common European viewpoint has emerged. This guideline for the treatment of segmental and nonsegmental vitiligo has been developed by the members of the Vitiligo European Task Force and other colleagues. It summarizes evidence‐based and expert‐based recommendations (S1 level).

Paraphenylenediamine, a contact allergen, induces oxidative stress and ICAM-1 expression in human keratinocytes.

In an investigation of the role of keratinocytes in the pre‐immunological phase of contract allergy, we have studied the effect parphenylendiamine (PPD) on cell proliferation, membrane lipid peroxidation and the expression of the intercellular adhesion molecule 1 (ICAM‐1). Because PPD undergoes rapid autoxidation in the culture medium, the effect of PPD‐modified medium on keratinocyte proliferation and ICAM‐l expression was also examined.

Nickel-keratinocyte interaction: a possible role in sensitization

Normal human keratinocytes and the keratinocyte‐derived cell lines NCTC 2544 and A 431, were exposed for different periods (i–5 days) to various concentrations (0·023–46.6 μg/ml) of nickel (Ni2+). A dose‐ and time‐dependent inhibition of cell growth and viability was observed. Cultures exposed to 2·3 μg Ni2+/ml showed approximately 50% cell survival at 5 days. An increase in release of interleukin I by keratinocytes was detected following culture for 24 h with a Ni2+ concentration of 2·3–11·5 μg/ml. Short periods of incubation (30 min) with these concentrations induced an activation of lipoxygenase in leucocytes from healthy subjects, without modifying cell viability. The results suggest that the percutaneous penetration of small amounts of Ni2+ can result in damage to keratinocytes and can initiate sensitization.

Blood levels of vitamin E, polyunsaturated fatty acids of phospholipids, lipoperoxides and glutathione peroxidase in patients affected with seborrheic dermatitis.

Plasma levels of vitamin E (Vit E) and polyunsaturated fatty acids of phospholipids (PUFA-PL) as well as erythrocyte glutathione peroxidase (GSH-Px) activity are significantly lower (P less than 0.001) in patients with seborrheic dermatitis (SD). both HIV seropositive or HIV sero-negative, than in control subjects. No differences are found between HIV sero-positive and sero-negative individuals with SD. The deficiency of PUFA-PL (mainly C20: 3 n-6, C20: 4 n-6 and C22: 6 n-3) which is accompanied by a significant increase of saturated palmitic and stearic acids (P less than 0.001), does not appear to be associated with an active lipoperoxidative process in the plasma. The significant blood deficiency of Vit E, GSH-Px, and particularly of PUFA-PL, may play a pathogenetic role in seborrheic dermatitis.

Skin surface lipids in HIV sero-positive and HIV sero-negative patients affected with seborrheic dermatitis.

Skin surface lipids of patients affected with seborrheic dermatitis both HIV sero-negative (C group) and HIV sero-positive (B group) have been studied by capillary Gas chromatography-Mass spectrometry (GC-MS) in comparison with normal age matched controls (A group) to determine whether, among the three groups of individuals, there were qualitative and quantitative changes in lipid class composition and in the fatty acid and alcohol components of lipid fractions. With regard to percent composition of skin surface lipid fractions, no significant differences were found between HIV sero-positive and HIV sero-negative patients with seborrheic dermatitis. The observed significant reduction of total lipids (micrograms/sq cm) in the sites affected with the disease in comparison with controls was associated with a slight but significant decrease of squalene (P less than 0.05) and with a corresponding increase of cholesterol and cholesterol esters (P less than 0.05). These abnormalities in lipid fractions and total lipids were not observed in the uninvolved skin of subjects with seborrheic dermatitis. Fatty acid and alcohol patterns of skin lipid fractions were not significantly different among the three groups of individuals.

Characterization of cultured nail matrix cells

BACKGROUNDnCultures of epidermal cells are commonly used to study skin biology and differentiation. Recently a method to culture nail matrix cells has been established.nnnOBJECTIVEnWe report the biologic characteristics of nail matrix cells in vitro compared with those of epidermal keratinocytes.nnnMETHODSnHuman nail matrix cells were isolated and cultured in defined medium. Electron-microscopic examination, growth rate, integrin expression and keratin synthesis pattern were evaluated. In addition, the cells were cultured in serum-containing medium.nnnRESULTSnNail matrix cells appear to be larger than human epidermal keratinocytes and, at the ultrastructural level, they contain a higher euchromatin/heterochromatin ratio and a lower nucleus/cytoplasm ratio and have a higher growth rate. The synthesis of hard keratins was detected at all calcium concentrations. Immunofluorescence analyses showed the expression of alpha 2, alpha 3, and alpha 6 integrin subunits. When cultured in serum-containing medium, nail matrix cells produced an outgrowth of epithelium and a spontaneous migration phenomenon associated with a tendency to stratify in a semilunar area that resembles the architecture of the nail matrix. The pluristratified epithelium showed characteristic markers of nail differentiation.nnnCONCLUSIONnCulture of nail matrix cells may represent a useful model to study the biologic properties of nail structure, alterations in some nail diseases and the effects of drugs.

Distribution of Merkel cells in adult human nail matrix

SIR, The nail apparatus has a rich nerve supply, and many nerve endings have been detected within and below the nail epithelium, particularly in the nail fold region. Merkel cells are neuroendocrine cells that are sparsely distributed in the epidermis, oral mucosa, vaginal mucosa, eccrine glands and hair follicles of numerous animal species. The distribution of Merkel cells in the human nail matrix has been investigated by Moll and Moll, who studied the fingernails of eight normal fetuses and three adults. The aim of this study was to clarify the presence and distribution of Merkel cells in the toenails and fingernails of children and adults. Nail matrix specimens were obtained from eight patients (mean age 19·4 years, range 13–46 years) with ingrowing toenails and from two autopsy fingernail matrix specimens. Control skin was taken from the volar forearm of each patient. Each specimen was immediately embedded in OCT compound, snap frozen in liquid nitrogen and stored at 180 8C until tested. Indirect immunofluorescence was performed on 5-mm-thick cryostat cut tissue sections. Correct orientation of the nail specimen was verified by examination of methylene blue-stained sections. The presence of Merkel cells in the nail matrix was studied using the mouse monoclonal antibody TROMA-1 (CAM5.2), obtained from Dr R.Kemler (Collège de France, Paris, France), reacting specifically with component 8 of the Moll cytokeratin catalogue, and the monoclonal antibody CK20 (IT-K5 20.3), a gift from Dr I.Moll (Heidelberg, Germany), which is selective for cytokeratin 20. The cytokeratins 8 and 20 are selective markers of Merkel cells. TROMA-1-positive and CK20-positive Merkel cells were detected in the ventral matrix of all the specimens. Merkel cells were sparsely distributed in both the proximal and the distal portions of the matrix. We studied six sections for each specimen giving a total of 60 sections. Each section showed from 11 to 35 cells (mean 20·7 cells; Fig. 1). Mean Merkel cell count in the nail matrix was 2 cells/mm of basal membrane length. Merkel cells were triangular or oval in shape and exhibited a high nuclear/ cytoplasmic ratio. They were always arranged as widely spaced single cells and frequently presented a vertical orientation. They were not restricted to the basal zone of the epidermis but were also found in the suprabasal layers of the nail matrix epithelium. In all sections, Merkel cells were more numerous at the tips of the nail matrix rete pegs. No differences were found in the distribution of Merkel cells between proximal and distal matrix or between toenail and fingernail specimens. We also did not find any difference in the Merkel cell distribution between specimens obtained from ingrowing toenails and specimens obtained from autoptic fingers. In control forearm skin, TROMA-1-positive and CK20positive Merkel cells were seen between basal keratinocytes and the underlying basement membrane. The mean number of Merkel cells for each forearm skin section was eight. An abundance of Merkel cells has been reported in the nails of fetuses, but previous studies on the distribution of Merkel cells in the nail matrix have reported that adult nails contain a very small number of Merkel cells. Our results, obtained using antibodies against CK8 and CK20 cytokeratins, are not in agreement with these findings, as we regularly detected Merkel cells among the nail matrix epithelium of adults. The mean number of 20·7 cells for nail matrix sections is similar to that reported in the fetal nail. All our specimens were taken from young patients, and the patient’s age may possibly influence the density of Merkel cells in the nail matrix as well as in other skin sites. Further studies are needed to clarify whether the Merkel cell density in the nail matrix decreases with age.

Characterization of the nail matrix basement membrane zone: an immunohistochemical study of normal nails and of the nails in Herlitz junctional epidermolysis bullosa

SIR. The nail is a specialized epithelial structure with characteristic structural and biological properties. In vitro studies have demonstrated that the cells of the nail matrix possess a high proliferative rate and are able to synthesize both skin-type and hair-type keratins. The integrin pattern shows characteristics of a hyperproliferative epithelium, with the expression of o2/Jl and oiii on the suprabastil layers, as described in psoriatic skin and during wound healing. A recent study has shown that, despite the ciiFlerencts between the epidermis and the nail matrix epithelium, the antigenic expression of basement membrane zone (BMZ) components is similar in both these structures and that there are no differences In the antigenic compositions of the BMZ between thediftercnl portions of the nail matrix. We report here an immunohistochemical study on the antigenic structure of the BMZ of the normal nail matrix and present evidence that, in Herlitz junctional epidermolysis bullosu (H-JEB), the BMZ of the nail matrix has the same immunostaining characteristics as detected on Ihe skin. Tissue specimens were obtained from eight patients with ingrowing toenalls and from a fetus, affected by H-JEB, which had an estimated gestational age of 18 weeks. Electron microscopy of the fetal skin had shown absence of hemidesmosomes. Each specimen was embedded in OCT compound, snap frozen in liquid nitrogen, and stored at -8()C until tested. An indirect immunolluorescence procedure, and immunoperoxidase staining using an avidinbiolin-peroxidase technique, were performed on cryostat-cut tissue sections (S/tm). The expression of hemidesmosome antigens was evaluated using antibodies against the a6 and ;i4 integrin subunits. bullous pemphigoid antigen, herpes gestationis antigen, and the monoclonal antibodies PlKl. HD-121 and AHS-7. The lamina lucida antigens were evaluated by using laminin antibody and the GB3 (Fig. la) and 19-DEJ-l antibodies. The monoclonal antibodies. LHi9 and 12 J were used to study the antigenic expression of anchoring filaments. The antigenic structure of the nail matrix lamina densa was