Associations between tobacco smoking status and patch test results-A cross-sectional pilot study from the Information Network of Departments of Dermatology (IVDK).

BACKGROUND: Earlier studies suggested a potential association between tobacco smoking and nickel sensitization, but little is known about other contact allergens. OBJECTIVES: To investigate the association of smoking status and contact sensitizations as well as subtypes of dermatitis, and to analyse the sensitization profiles of tobacco smokers. PATIENTS AND METHODS: Within the Information Network of Departments of Dermatology (IVDK), we performed a cross-sectional multicentre pilot study comprising 1091 patch-tested patients from 9 departments, comparing 541 patients with a history of cigarette smoking (281 current and 260 former smokers) with 550 never-smokers. RESULTS: We could not confirm the previously reported association between nickel sensitization and tobacco smoking. Moreover, sensitizations to other allergens, including colophony, fragrance mix I, Myroxylon pereirae and formaldehyde, were not increased in cigarette smokers compared with never smokers. Hand dermatitis (50.6% vs. 33.6%) and occupational cause (36.2% vs. 22.5%) were significantly more frequent among cigarette smokers compared with never-smokers as shown by non-overlapping 95% confidence intervals. CONCLUSIONS: Although our study does not allow a firm conclusion on whether smoking status contributes to certain contact sensitizations, it confirms an association of smoking with hand dermatitis and occupational cause.

Contact sensitization to benzisothiazolinone: IVDK-data of the years 2002 to 2021.

BACKGROUND: Benzisothiazolinone (BIT; CAS no. 2634-33-5) is used as a biocide in various products, including water-based paints, metalworking fluids, and household products. In recent years, increasing sensitization rates have been observed in Europe. OBJECTIVE: To describe a time trend of sensitization to BIT, analyse concomitant reactions, and identify patients with increased risk of BIT sensitization. METHODS: Retrospective analysis of data from 26 739 patients patch tested with BIT, sodium salt, 0.1% petrolatum as part of several special test series within the Information Network of Departments of Dermatology (IVDK), 2002 to 2021. RESULTS: Positive reactions to BIT were noted in 771 patients (2.9%). Sensitization frequency varied over time and increased in recent years, peaking at 6.5% in 2020. Painters and metalworkers handling metalworking fluids, but not cleaners, had a significantly increased risk of BIT sensitization. From our data, there is no evidence of immunological cross-reactivity between BIT and other isothiazolinones. CONCLUSION: The increasing frequency of sensitization justifies adding BIT to the baseline series. More research on the clinical relevance of positive patch test reactions to BIT and the cause for the rising numbers of BIT sensitization is needed.

A negative breakdown test in a fragrance mix I-positive patient does not rule out contact allergy to its fragrance constituents.

BACKGROUND: In about half of the patients reacting positive to fragrance mix I (FM I), breakdown testing remains negative. This raises the question of whether the reaction to FM I is false-positive, or the breakdown test is false-negative. OBJECTIVES: To identify characteristics and sensitization patterns of patients positive to FM I, but not to its fragrance constituents. PATIENTS AND METHODS: Retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK) between 2005 and 2019. Three patient groups were defined according to their reaction pattern: Group I, FM I positive and ≥1 single fragrance positive in the breakdown test (n = 1912); Group II, FM I positive and breakdown test negative (n = 1318); Group III, FM I negative (n = 19 790). RESULTS: Regarding the pattern of concomitant reactions to other fragrances, Group II had an intermediate position between Group I and Group III. In other respects (age and sex distribution, frequency of sensitization to non-fragrance baseline series allergens), Group II rather resembled Group I. CONCLUSIONS: Not every positive reaction to FM I in patients with negative breakdown tests is false-positive. There may be false-negative reactions to the single fragrance components when patch tested at 1% pet. Raising patch concentrations of some single fragrances is recommended.

A variant of the CXCL11 gene may influence susceptibility to contact allergy, particularly in polysensitized patients.

BACKGROUND: Hereditary factors may influence individual susceptibility to contact allergy. OBJECTIVES: To investigate genetic variants with impacts on early inflammatory reactions and T cell functions that possibly increase the risk of contact allergy. PATIENTS AND METHODS: Three hundred and seventy two patients undergoing patch testing were recruited from the Information Network of Departments of Dermatology (IVDK). Of these, 133 were monosensitized and 239 were polysensitized, defined as reacting to three or more unrelated sensitizers. Within the polysensitized individuals, a subgroup with at least one particularly strong patch test reaction (strong reactors; n = 194) was considered. Three hundred and forty-seven blood bank donors served as controls. Fifteen genetic variants in 13 genes were analysed. RESULTS: The homozygous variant CXCL11 AA genotype (rs6817952) was significantly more frequent among polysensitized patients (10 of 239 = 4.2%; p = 0.0048; odds ratio 7.49; 95%CI: 1.7-36.1) than among monosensitized patients (2.2%) and in the control group (0.6%). None of the remaining genetic variants investigated were characterized by similarly strong associations. However, the significance was lost after correction for multiple comparisons. CONCLUSIONS: The homozygous variant CXCL11 genotype is associated with an increased risk of contact allergy. To confirm this exploratory finding, further independent studies are needed.

DKG statement on the use of metal alloy discs for patch testing in suspected intolerance to metal implants.

Intolerance reactions to metal implants may be caused by metal allergy. However, prior to implantation, 'prophetic'/prophylactic patch testing should not be performed. Pre-implant patch testing should only be done to verify or exclude metal allergy in patients with a corresponding history. In case of implant-related complications - in particular following replacement arthroplasty - such as pain, effusion, skin lesions, reduced range of motion or implant loosening, orthopedic causes should be ruled out first. Workup of suspected metal implant allergy should then be done using the DKG standard series, which includes nickel, cobalt, and chromium preparations. Various studies assessing the usefulness of metal alloy discs for patch testing have shown this particular approach to be ineffective with respect to providing reliable information on metal allergy. Any positive reaction in such tests cannot be assigned to a specific metal contained within the alloy. Furthermore, there is a risk of broad and indiscriminate use of these readily available discs. Accordingly, given the lack of additional benefit compared to patch testing with standardized metal salt preparations, we do not recommend patch testing with metal alloy discs.

Vascular endothelial growth factor gene polymorphisms as prognostic markers for ocular manifestations in pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is a heritable disorder affecting the skin, eyes and cardiovascular system. It is caused by mutations in the ABCC6 gene and its clinical picture is highly variable. PXE often leads to severe visual impairment due to the development of choroidal neovascularisation (CNV). CNV in PXE-associated retinopathy is believed to be mediated by the action of vascular endothelial growth factor (VEGF). The objective of the present study was to evaluate a possible impact of variations in the VEGFA gene on ocular manifestations of PXE. For this purpose, we evaluated the distribution of 10 single nucleotide polymorphisms (SNPs) in the promoter and coding region of the VEGFA gene in DNA samples from 163 German patients affected by PXE and in 163 healthy control subjects. Haplotype analysis of SNPs c.-1540A>C, c.-460C>T, c.-152G>A, c.405C>G, c.674C>T, c.1032C>T, c.4618C>T and c.5092C>A revealed that the haplotype CTGGCCCC was associated with PXE (OR 2.05, 95% CI 1.33-3.15, P(corrected) = 0.01). Furthermore, five SNPs showed significant association with severe retinopathy. The most significant single SNP association was c.-460C>T (OR 3.83, 95% CI 2.01-7.31, P(corrected) = 0.0003). Logistic regression analysis identified the c.-460T and the c.674C alleles as independent risk factors for development of severe retinopathy. Our findings suggest an involvement of VEGF in the pathogenesis of ocular PXE manifestations. VEGF gene polymorphisms might prove useful as prognostic markers for the development of PXE-associated retinopathy and permit earlier therapeutic intervention in order to prevent loss of central vision, one of the most devastating consequences of this disease.

Quantitative repeated open application testing with a rinse-off product in methyldibromo glutaronitrile-sensitive patients: results of the IVDK.

BACKGROUND: While the use of methyldibromo glutaronitrile (MDBGN) in leave-on products is clearly associated with high sensitization or elicitation risk, such a clear-cut relation could be questioned with regard to rinse-off products. OBJECTIVE: The objective of this study was to find a maximum non-eliciting concentration for rinse-off products in MDBGN patch test-positive patients. PATIENTS AND METHODS: We performed a use-related test [repeated open application test (ROAT)] in patients sensitized to MDBGN with a liquid soap containing three concentrations of MDBGN (50, 200, and 400 p.p.m. MDBGN, respectively). The soap at 50 p.p.m. was used twice daily for 4 weeks. If no reaction of the skin was observed, the product with the next higher concentration was used for another 4 weeks, etc. RESULTS: In total, 32/37 evaluated cases [86.5%; lower exact one-sided 95% confidence limit (CL): 73.7%] did not react to any of the preparations. The remaining reacted as follows: 1/37 reacted to 50 p.p.m., 3/37 to 200 p.p.m., and 1/37 to 400 p.p.m. The cumulative non-response to 50 p.p.m. was 97.3% (lower CL: 87.8%). CONCLUSIONS: The majority of subjects sensitized to MDBGN-tolerated rinse-off products containing a maximum concentration of 400 p.p.m. A concentration in rinse-off products in the range of 50 p.p.m. could be regarded as safe for most individuals already sensitized. These concentrations will presumably prevent induction (sensitization) also.

Quantitative patch and repeated open application testing in hydroxyisohexyl 3-cyclohexene carboxaldehyde sensitive-patients.

OBJECTIVE: To identify the concentration of the fragrance compound hydroxyisohexyl 3-cyclohexene carboxaldehyde (INCI) (HICC) that is sufficiently low not to cause an allergic reaction in patients with proven sensitization. METHODS: Repeated open application testing (ROAT) in 64 subjects with 2 preparations (perfume and cream) in different concentration (0.005-2.5%). Confirmatory patch testing with four preparations in two different concentrations (2.5% and 5%). RESULTS: The concentrations of HICC being tolerated by 90% of those sensitized to HICC are estimated as <88.2 ppm (cream) and <270 ppm (perfume) equivalent to 1.2 microg/cm(2) (perfume) and 4.9 microg/cm(2) (cream). Patch test preparations differed with regard to sensitivity (88.5-98.1%) and specificity (37.5-87.5%) against the ROAT result as external criterion. ROAT concentrations and the reaction strength in patch testing were inversely correlated (Kendall's tau-b: 0.69), both indicating the existence of different degrees of susceptibility. CONCLUSION: To protect 90% (50%) of people sensitized, the use concentration should be in the range of 0.009-0.027% (0.18-0.34%), depending on the product type. Taking into account these results, excessive concentrations should be avoided, as this would continue to sensitize people. Close monitoring is indispensable to prove the efficacy of any recommendations aiming to prevent induction.

Chromated metal products may be hazardous to patients with chromate allergy.

BACKGROUND: Hidden allergen exposure may contribute to persistence and relapse of chromate dermatitis. According to case reports, chromated metal products, such as screws, fittings, etc., may be relevant allergen sources for patients sensitized to chromate. OBJECTIVES: To examine concomitant patch test reactivity to potassium dichromate 0.5% petrolatum (pet.) and three different types of chromated metal rings. PATIENTS/METHODS: Patients with proven or suspected chromate allergy were patch tested with potassium dichromate 0.5% pet. and three different types of chromated metal rings (yellow, olive, and black). Hexavalent chromium Cr(VI) release from the patch tested rings was chemically analysed. RESULTS: Ninety-five patients were tested: 49/95 (52%) reacted to potassium dichromate and 25/95 (26%) reacted to black chromated rings. Reactions to chromated rings exclusively occurred in patients reacting to potassium dichromate. Of 20 patients with a strong reaction to potassium dichromate, 14 reacted to black chromated rings. These were shown to have a high Cr(VI) release. Only two patients reacted to the other chromated rings, which had a very low Cr(VI) release. CONCLUSIONS: Handling chromated metal products must be regarded a hazard to chromate-sensitive patients, in particular those with a strong sensitization.

Gene expression profiling of ABC transporters in dermal fibroblasts of pseudoxanthoma elasticum patients identifies new candidates involved in PXE pathogenesis.

Mutations in the ABCC6 gene, encoding the multidrug resistance-associated protein 6 (MRP6), cause pseudoxanthoma elasticum (PXE). This heritable disorder leads to pathological alterations in connective tissues. The implication of MRP6 deficiency in PXE is still unknown. Moreover, nothing is known about a possible compensatory expression of other ATP binding-cassette (ABC) transporter proteins in MRP6-deficient cells. We investigated the gene expression profile of 47 ABC transporters in human dermal fibroblasts of healthy controls (n=2) and PXE patients (n=4) by TaqMan low-density array. The analysis revealed the expression of 37 ABC transporter genes in dermal fibroblasts. ABCC6 gene expression was not quantifiable in fibroblasts derived from PXE patients. Seven genes (ABCA6, ABCA9, ABCA10, ABCB5, ABCC2, ABCC9 and ABCD2) were induced, whereas the gene expression of one gene (ABCA3) was decreased, comparing controls and PXE patients (with at least twofold changes). We reanalyzed the gene expression of selected ABC transporters in a larger set of dermal fibroblasts from controls and PXE patients (n=6, each). Reanalysis showed high interindividual variability between samples, but confirmed the results obtained in the array analysis. The gene expression of ABC transporter genes, as well as lineage markers of PXE, was further examined after inhibition of ABCC6 gene expression by using specific small-interfering RNA. These experiments corroborated the observed gene expression alterations, most notably in the ABCA subclass (up to fourfold, P<0.05). We therefore conclude that MRP6-deficient dermal fibroblasts exhibit a distinct gene expression profile of ABCA transporters, potentially to compensate for MRP6 deficiency. Moreover, our results point to a function for ABCC6/MRP6 in sterol transport, as sterols are preferential regulators of ABCA transporter activity and expression. Further studies are now required to uncover the role of ABCA transporters in PXE.

The local calcification inhibitor matrix Gla protein in pseudoxanthoma elasticum.

OBJECTIVES: Recent studies have revealed the involvement of calcification inhibitory proteins in the pathogenesis of pseudoxanthoma elasticum (PXE). DESIGN AND METHODS: We analyzed serum concentrations of the calcification inhibitor matrix Gla protein (MGP) in a large cohort of patients suffering from PXE (n=101), 34 first-degree relatives and 67 healthy controls. Moreover, we determined the distribution of the two MGP promoter polymorphisms c.-7G>A and c.-138T>C in the three cohorts. RESULTS: We found significantly lower total MGP concentrations in the sera of PXE patients compared to healthy controls (p=0.0002). Furthermore, higher serum MGP concentrations could be correlated with a later PXE onset. Analysis of MGP promoter polymorphism frequencies revealed one MGP haplotype to be a potential protective co-factor in PXE. CONCLUSIONS: Our findings point to a role of the local calcification inhibitor MGP in PXE manifestation.

Circulating P-, L- and E-selectins in pseudoxanthoma elasticum patients.

OBJECTIVES: Pseudoxanthoma elasticum (PXE) is a hereditary disorder predominantly affecting the skin, retina and vascular system. The aim of this study was to measure cell adhesion molecules in PXE patients. DESIGN AND METHODS: Soluble P-, E- and L-selectins were measured in 61 non-consanguineous PXE patients. The distribution of the variants E-selectin S128R and P-selectin T715R were determined. RESULTS: P-selectin concentrations were significantly increased in male and female PXE patients. Furthermore, P-selectin levels correlated with the ABCC6 gene status of the PXE patients. Patients harboring two mutant ABCC6 alleles had 1.5-fold increased P-selectin concentrations in comparison to patients with at least one wild-type allele. E- and L-selectin levels were within normal range and the allelic frequencies of the investigated polymorphisms did not differ between patients and age- and sex-matched controls. CONCLUSIONS: Our data show elevated P-selectin levels in PXE patients potentially due to oxidative stress and elevated protease activity in PXE.

Elevated serum levels of intercellular adhesion molecule ICAM-1 in Pseudoxanthoma elasticum.

BACKGROUND: Pseudoxanthoma elasticum (PXE, OMIM 177850 and 264800) is a rare heritable disorder predominantly affecting the skin, the eyes and the vascular system. The disease is caused by mutations in the ABCC6 gene and is characterized by calcification and extracellular matrix remodeling, including alterations of the vessel walls. Here, we investigated the cell adhesion molecules ICAM-1 in PXE patients. METHODS: Soluble ICAM-1 was determined in 58 non-consanguineous PXE patients by quantitative sandwich enzyme immunoassay. The allelic frequencies of the ICAM-1 variant p.K469E were analyzed in patients and age- and sex-matched controls. RESULTS: Soluble ICAM-1 levels were significantly elevated in male and female PXE patients (p<0.02 and p<0.001, respectively). In addition, the ICAM-1 concentration correlated with the ABCC6 gene status of the PXE patients. The ICAM variant p.K469E genotypes were not different in PXE patients and age- and sex-matched controls. CONCLUSIONS: Our data show for the first time increased ICAM-1 concentrations in PXE patients, potentially due to the chronic oxidative stress and elevated protease activity followed by extracellular matrix remodeling which have been previously observed in PXE patients.

Complement factor H variant p.Y402H in pseudoxanthoma elasticum patients.

Pseudoxanthoma elasticum (PXE) is a hereditary disorder predominantly affecting the eyes, the skin, and the vascular system. The subretinal neovascularization and retinal hemorrhages leading to the loss of central vision in PXE are similar to the process observed in age-related macular degeneration (AMD). The complement factor H (CFH) variant c.1277T > C (p.Y402H) is a recently discovered risk factor for AMD. The aim of this study was to analyze whether this CFH variant is a secondary genetic risk factor for PXE. Therefore, the genotypes of CFH c.1277T > C (p.Y402H) were determined in 189 German PXE patients and 189 age- and sex-matched controls. The allelic frequencies of the investigated variant did not differ between patients and controls. The frequencies were 33%, 56%, and 11% for wild-type, heterozygous, and homozygous genotypes in the PXE patients and 36%, 51%, and 13% in the control cohort, respectively. Further, no significant associations were identified when allele carriers were analyzed or after adjustment for sex, age, smoking, organ involvement, hypertension, or age at disease onset. No significant genotype-phenotype correlation was detected. In conclusion, our data reliably show that the CFH variant c.1277T > C (p.Y402H) is not a genetic risk factor for PXE.

Patch testing in children--recommendations of the German Contact Dermatitis Research Group (DKG).

Allergic contact dermatitis occurs frequently in children. Patch testing is needed to identify the responsible allergens and should be performed in children. We recommend a panel of 12 contact allergens as a standard series in children from 6-12 years. Four additional contact allergens should be tested in case of a positive history or suggestive clinical picture. For patch testing in children, the allergens should be applied for 24 hours and the readings should be performed at 48 and 72 hours. Standardized patch testing makes it possible to systematically investigate allergic contact dermatitis and identify relevant allergens in children.

Mutational analysis of the ABCC6 gene and the proximal ABCC6 gene promoter in German patients with pseudoxanthoma elasticum (PXE).

Pseudoxanthoma elasticum (PXE) is a genetic disorder characterized by calcification of elastic fibers in dermal, ocular, and cardiovascular tissues. Recently, ABCC6 mutations were identified as causing PXE. In this follow-up study we report the investigation of 61 German PXE patients from 53 families, hitherto the largest cohort of German PXE patients screened for the complete ABCC6 gene. In addition, we characterized the proximal ABCC6 promoter of PXE patients according to mutation. In this study we identified 32 disease-causing ABCC6 variants, which had been described previously by us and others, and 10 novel mutations (eight missense mutations and two splice site alterations). The mutation detection rate among index patients was 87.7%. Frequent alterations were the PXE-mutations p.R1141X, Ex23,_Ex29del, and c.2787+1G > T. In the ABCC6 promoter we found the polymorphisms c.-127C > T, c.-132C > T, and c.-219A > C. The difference in the c.-219A > C frequencies between PXE patients and controls were determined as statistically significant. Interestingly, c.-219A > C is located in a transcriptional activator sequence of the ABCC6 promoter and occurred in a binding site for a transcriptional repressor, predominantly found in genes that participate in lipid metabolism. Obtaining these genetic data signifies our contribution to elucidating the pathogenetics of PXE.

New ABCC6 gene mutations in German pseudoxanthoma elasticum patients.

Pseudoxanthoma elasticum (PXE; OMIM 177850 and 264800) is a rare heritable disorder of the connective tissue affecting the extracellular matrix of the skin, eyes, gastrointestinal system, and cardiovascular system. It has recently been found that mutations in the ABCC6 gene encoding the multidrug resistance-associated protein (MRP) 6 cause PXE. This study examined novel mutations in the ABCC6 gene in our cohort of 76 German PXE patients and 54 unaffected or not yet affected relatives with a view to expanding the known mutational spectrum of the gene. Mutational analysis was performed using denaturing high-performance liquid chromatography and direct sequencing. The mutational screening revealed a total of 22 different ABCC6 sequence variations. We identified seven novel and four previously described PXE-associated mutations as well as eight novel neutral ABCC6 sequence variants. The new PXE-associated mutations included five missense mutations, one single base pair deletion, and one larger out-of-frame deletion. We suspect that the novel missense mutations lead to an impaired function of MRP6. Both deletions are predicted to result in a dysfunctional MRP6 protein. The seven new ABCC6 mutations were not present in 200 alleles from healthy blood donors which served as a control cohort. Most of the PXE patients who were found to carry PXE-causing ABCC6 mutations were assumed to manifest the PXE phenotype because of a compound heterozygous genotype. However, a genotype-phenotype correlation could not be established for the detected ABCC6 mutations. In summary, our data give a further insight into the spectrum of ABCC6 mutations in PXE patients.