Dysregulation of the Skin-Liver Axis in Prurigo Nodularis: An Integrated Genomic, Transcriptomic, and Population-Based Analysis

Pruritus has long been linked to hepatic dysfunction; however, there are limited data characterizing the association between liver disease and prurigo nodularis (PN), a chronic inflammatory skin disease featuring severe pruritis. We thus conducted a cross-sectional analysis of hepatic comorbidities in PN patients using TriNetX, a large global health research network. This analysis revealed that PN patients had a higher risk (p < 0.001) of developing liver cirrhosis, acute and subacute hepatic failure, inflammatory liver disease, chronic hepatitis, nonalcoholic steatohepatitis, portal hypertension, fatty liver, chronic passive congestion of the liver, and hepatocellular carcinoma compared with healthy controls. The cumulative incidence of liver disease was about three times higher in PN patients compared with healthy controls. These findings provided the basis for translational studies to investigate a genetic mechanism for this association. Cutaneous transcriptomic analysis performed on PN patients revealed the dysregulation of genes related to hepatic failure in lesional PN compared with both nonlesional PN and control skin. Similarly, gene set variation analysis (GSVA) revealed a significantly increased (p < 0.05) activation of liver metabolism, chronic hepatic failure, acute hepatic failure, cholestatic liver disease, polycystic liver disease, and hepatocellular carcinoma pathways in lesional PN compared with control skin. A subsequent genome-wide association study (GWAS) identified shared single-nucleotide polymorphisms (SNPs) in the genes AR, EDIL3, MACROD2, PCSK5, RUNX1T1, TENM4, and ZEB2 between PN and liver disease from the FinnGen cohort. Significant dysregulation of the skin-liver axis in PN patients may explain the increased incidence and severity of hepatic comorbidities and help identify future therapeutic targets for PN.

A Polygenic Risk Score for Predicting Racial and Genetic Susceptibility to Prurigo Nodularis

Prurigo nodularis (PN) is an understudied inflammatory skin disease characterized by pruritic, hyperkeratotic nodules. Identifying the genetic factors underlying PN could help to better understand its etiology and guide the development of therapies. In this study, we developed a polygenic risk score that predicts a diagnosis of PN (OR = 1.41, P = 1.6 × 10-5) in two independent and continentally distinct populations. We also performed GWASs, which uncovered genetic variants associated with PN, including one near PLCB4 (rs6039266: OR = 3.15, P = 4.8 × 10-8) and others near TXNRD1 (rs34217906: OR = 1.71, P = 6.4 × 10-7; rs7134193: OR = 1.57, P = 1.1 × 10-6). Finally, we discovered that Black patients have over a two-times greater genetic risk of developing PN (OR = 2.63, P = 7.8 × 10-4). Combining the polygenic risk score and self-reported race together was significantly predictive of PN (OR = 1.32, P = 4.7 × 10-3). Strikingly, this association was more significant with race than after adjusting for genetic ancestry. Because race is a sociocultural construct and not a genetically bound category, our findings suggest that genetics, environmental influence, and social determinants of health likely affect the development of PN and may contribute to clinically observed racial disparities.

Single-cell RNA sequencing defines disease-specific differences between chronic nodular prurigo and atopic dermatitis

BACKGROUND

Chronic nodular prurigo (CNPG) is an inflammatory skin disease that is maintained by a chronic itch-scratch cycle likely rooted in neuroimmunological dysregulation. This condition may be associated with atopy in some patients, and there are now promising therapeutic results from blocking type 2 cytokines such as IL-4, IL-13, and IL-31.

OBJECTIVES

This study aimed to improve the understanding of pathomechanisms underlying CNPG as well as molecular relationships between CNPG and atopic dermatitis (AD).

METHODS

We profiled skin lesions from patients with CNPG in comparison with AD and healthy control individuals using single-cell RNA sequencing combined with T-cell receptor sequencing.

RESULTS

We found type 2 immune skewing in both CNPG and AD, as evidenced by CD4+ helper T cells expressing IL13. However, only AD harbored an additional, oligoclonally expanded CD8A+IL9R+IL13+ cytotoxic T-cell population, and immune activation pathways were highly upregulated in AD, but less so in CNPG. Conversely, CNPG showed signatures of extracellular matrix organization, collagen synthesis, and fibrosis, including a unique population of CXCL14-IL24+ secretory papillary fibroblasts. Besides known itch mediators such as IL31 and oncostatin M, we also detected increased levels of neuromedin B in fibroblasts of CNPG lesions compared with AD and HC, with neuromedin B receptors detectable on some nerve endings.

CONCLUSIONS

These data show that CNPG does not harbor the strong disease-specific immune activation pathways that are typically found in AD but is rather characterized by upregulated stromal remodeling mechanisms that might have a direct impact on itch fibers.

Transcriptomic, Epigenomic, and Neuroanatomic Signatures Differ in Chronic Prurigo, Atopic Dermatitis, and Brachioradial Pruritus

Scratching and scratch-induced injuries, including neuroanatomical alterations, are key characteristics of chronic pruritus entities of different origins. The aim of this study was to link gene expression (array hybridization, qPCR) with DNA methylation (array hybridization) and neuroanatomy (PGP9.5 staining) in chronic nodular prurigo (CNPG), atopic dermatitis (AD), brachioradial pruritus (BRP), and matched healthy controls. Specific signatures of gene expression and DNA methylation clearly discriminated pruritic lesional skin from nonpruritic skin in CNPG and from healthy skin of volunteers, respectively. Although intraepidermal nerve fiber density was indiscriminately reduced, the level of epidermal branching, assessed by a semiquantitative pattern analysis, differentiated the entities (CNPG > BRP > AD). Correspondingly, repellent SEMA3A showed the highest expression in AD, whereas axonal growth-promoting nerve GF was most prominent in CNPG and BRP. Overexpression of genes for nerve fiber regeneration (NELL2/NFKB/ARTN) was found in AD and CNPG but not in BRP. Our findings suggest that differential branching patterns rather than mere innervation density separate chronic itch conditions and reflect disease-specific local expression profiles. In pruritic dermatoses (AD and CNPG), nerve injury and subsequent sprouting may primarily result from chronic scratching, whereas genuine neuropathy is expected to underlie BRP.

Aberrant Expression of Histamine-independent Pruritogenic Mediators in Keratinocytes may be Involved in the Pathogenesis of Prurigo Nodularis

Prurigo nodularis is a highly pruritic and hyperplastic chronic dermatosis with unknown pathogenesis. Many pruritogenic mediators, including nerve growth factor, interleukin (IL)-31, thymic stromal lymphopoietin, and endothelin-1, are implicated in chronic itch and inflammation. This study investigated the mRNA levels and immunoreactivity of the nerve growth factor, IL-31, thymic stromal lymphopoietin, and endothelin axes in both lesional and perilesional skin in prurigo nodularis by using quantitative real-time PCR and immunohistochemistry studies. The nerve growth factor high-affinity receptor tyrosine kinase receptor A was upregulated while the low affinity receptor p75 neurotrophin receptor was downregulated in prurigo nodularis lesions. Downregulated expression of IL-31/IL-31 receptor A and endothelin-3/endothelin receptor B and upregulation of thymic stromal lymphopoietin receptor were found in prurigo nodularis lesions. Aberrant expression of nerve growth factor, IL-31, thymic stromal lymphopoietin and endothelin axes was found in prurigo nodularis lesions, especially in the epidermis, indicating the importance of keratinocytes in prurigo nodularis pathogenesis.

Genotype-phenotype correlation in Chinese patients with dystrophic epidermolysis bullosa pruriginosa

Dystrophic epidermolysis bullosa pruriginosa (DEB-Pr) is a rare variant of dystrophic epidermolysis bullosa (DEB) due to dominant or recessive mutations in the COL7A1 gene. More than 40 mutations in COL7A1 have been described in DEB-Pr. The aim of this study was to understand the genotype-phenotype correlation in Chinese patients with DEB-Pr. Three Chinese families with typical clinical features of DEB-Pr were studied. The results were analysed in association with the eight Chinese DEB-Pr patients reported in the literature. In the three Chinese families with DEB-Pr, we found two dominant cases with G1773R and c.6900+1G>C mutations, and one case with heterozygous G2701W mutation of uncertain inheritance mode. In the 10 Chinese patients with dominant type of DEB-Pr, 7 glycine substitutions and three splicing site mutations of exon 87 skipping were identified. Glycine substitution mutations in the triple helix region and exon 87 skipping, leading to the in-frame deletion of 23 amino acid residues in the triple-helix, are often seen in Chinese patients with dominant DEB-Pr, although the glycine substitutions are also frequently present in dominant DEB.

Prurigo pigmentosa: An underdiagnosed disease in patients of Iranian descent?

BACKGROUND

Prurigo pigmentosa (PP) is a rare inflammatory disease of the skin typified by recurrent, pruritic erythematous macules and papules that resolve leaving behind netlike pigmentation.

OBJECTIVE

PP is diagnosed most commonly in Japanese women. Preponderance of the disease in other ethnic populations has yet to be identified.

METHODS

We conducted a clinicopathologic case study in 4 Iranian women.

RESULTS

The clinical diagnosis of PP was confirmed by typical histopathologic findings, elucidating the morphologic spectrum of the disease.

LIMITATIONS

The small number of patients in this study is a limitation.

CONCLUSION

We suspect that PP may have a proclivity in the Iranian population.

Familial clustering of Leiomyomatosis peritonealis disseminata: an unknown genetic syndrome?

BACKGROUND

Leiomyomatosis peritonealis disseminata (LPD) is defined as the occurrence of multiple tumorous intraabdominal lesions, which are myomatous nodules. LPD is a rare disease with only about 100 cases reported. The usual course of LPD is benign with the majority of the patients being premenopausal females. Only two cases involving men have been reported, no syndrome or familial occurrence of LPD has been described.

CASE PRESENTATION

We describe a Caucasian-American family in which six members (three men) are diagnosed with Leiomyomatosis peritonealis disseminata (LPD) and three deceased family members most likely had LPD (based on the autopsy reports). Furthermore we describe the association of LPD with Raynaud's syndrome and Prurigo nodularis.

CONCLUSION

Familial clustering of Leiomyomatosis peritonealis disseminata (LPD) has not been reported so far. The etiology of LPD is unknown and no mode of inheritance is known. We discuss possible modes of inheritance in the presented case, taking into account the possibility of a genetic syndrome. Given the similarity to other genetic syndromes with leiomyomatosis and skin alterations, we describe possible similar genetic pathomechanisms.

Thalidomide in the management of epidermolysis bullosa pruriginosa

Epidermolysis bullosa (EB) pruriginosa is a distinctive clinical subtype of dystrophic EB. We report a patient with dominant dystrophic EB pruriginosa, who had an excellent response to systemic thalidomide treatment. The mechanism of action of thalidomide in the management of pruriginous disorders is not yet completely understood. Most recent studies point towards an immunomodulatory action of thalidomide that may suppress excessive production of tumour necrosis factor-alpha and may downregulate certain cell surface adhesion molecules involved in leucocyte migration.

The clinical spectrum of dystrophic epidermolysis bullosa

BACKGROUND

Dystrophic epidermolysis bullosa (DEB) is a genodermatosis resulting from mutations in COL7A1, the gene encoding type VII collagen. The site and specific nature of the underlying mutation determine the clinical phenotype, which ranges widely from a severe mutilating condition to a relatively mild disorder.

OBJECTIVES

To document the clinical spectrum of DEB within a defined complete population.

METHODS

Since 1992, when compilation of the U.K. epidermolysis bullosa register began, an exhaustive search for DEB sufferers within the Scottish population has been undertaken and their clinical features comprehensively recorded.

RESULTS

One hundred and twenty-eight DEB sufferers have been identified within the Scottish population. In descending order, the frequencies of the different forms of DEB were dominant DEB (DDEB) in 88 individuals (68%), DEB of uncertain inheritance in 24 (19%) and recessive DEB (RDEB) in 16 patients (13%). Within this latter group, nine (7%) had the mutilating Hallopeau-Siemens subtype (RDEB-HS), five (4%) had localized (RDEB-loc) and two (2%) had a predominantly flexural (inverse) form of RDEB. During the study, two patients with RDEB died from squamous cell carcinomas (SCCs), one originating in the skin and the second arising in the oesophagus. Gastrointestinal problems such as dysphagia, constipation and anal fissures, and restriction of mouth opening were experienced by the majority of patients with RDEB and by a significant minority of DDEB sufferers. Pseudosyndactyly was most severe in RDEB-HS, all those over 9 years of age having mitten deformities of the hands. Milder pseudosyndactyly or flexion contractures of the fingers were present in younger patients with this subtype, in most adults suffering from other subtypes of RDEB and in 6% of those with DDEB. External ear involvement, a feature not often reported in DEB, was common in RDEB and also occurred in a minority of those with DDEB. Pruriginous lesions and albopapuloid lesions were each present in both DDEB and RDEB.

CONCLUSIONS

Most patients with DEB have relatively mild dominantly inherited disease, only a minority suffering from severe recessive subtypes. Scarring, gastrointestinal involvement, albopapuloid lesions and a pruriginosa-like pattern each occur in both DDEB and RDEB. With increasing age, SCC is a major cause of morbidity and mortality.

A candidate gene analysis of three related photosensitivity disorders: cutaneous lupus erythematosus, polymorphic light eruption and actinic prurigo

BACKGROUND

Polymorphic light eruption (PLE) is a common inherited photosensitivity disorder, which may predispose to several related but distinct conditions, including subacute cutaneous lupus erythematosus (SCLE), discoid lupus erythematosus (DLE) and actinic prurigo (AP).

OBJECTIVES

To examine specific candidate genes for shared susceptibility alleles between these related phenotypes.

METHODS

Eighty-five caucasian patients with annular SCLE or DLE were recruited, in addition to 102 first-degree relatives. The prevalence of PLE in both the patient and relative groups was determined by detailed interview and clinical examination. Eighty-five patients with pure PLE and 59 patients with AP were also recruited. Candidate genes were analysed by typing of single nucleotide polymorphisms of IL10 (-1082 G/A and -819 C/T), FCGR2A (131 R/H), SELE (128 S/R), ICAM1 (241 G/R and 469 E/K), IL1A (+ 4845 G/T), IL1B (-511 C/T and + 3954 C/T), IL1RN (+ 2018 T/C) and TNF (-308 G/A) using polymerase chain reaction (PCR) with sequence-specific primers and 5'-nuclease PCR.

RESULTS

A significant association was found between SCLE and the rare TNF -308 A allele when compared with patients with DLE (P = 0.043), PLE (P = 0.001), AP (P < 0.001) and healthy controls (P < 0.001). However, there was strong linkage disequilibrium between TNF -308 A and the HLA A*01, B*08, DRB1*0301 haplotype. A negative association was also found between SCLE and the IL1B + 3954 T allele (P = 0.039), but the significance was lost on correction for multiple testing.

CONCLUSIONS

We have demonstrated the association of SCLE with the rare TNF -308 A allele, which may be pathogenic or, alternatively, a marker allele for the extended HLA A*01, B*08, DRB1*0301 haplotype that is associated with a number of autoimmune conditions. Although many of the other loci that we chose failed to demonstrate an association, a candidate gene approach remains the most logical one, and the most likely to yield positive results in the future.

Actinic prurigo: Clinical features and HLA associations in a Canadian Inuit population

BACKGROUND

Actinic prurigo (AP) is an idiopathic familial photodermatitis. AP of the Inuit is rarely reported and poorly characterized.

OBJECTIVE

Our purpose was to examine the clinical features and HLA associations of AP in an Inuit population.

METHODS

Thirty-seven Inuit subjects with AP were administered a questionnaire and underwent a cutaneous examination. Other causes of photosensitivity were excluded. HLA class I typing was performed by polymerase chain reaction and sequence-specific primers and class II typing by polymerase chain reaction and sequence-specific oligonucleotide probes.

RESULTS

Subjects were 81.1% female, 67.6% had a family history of photosensitivity, and all experienced seasonal variation. The average age at onset of photosensitivity was 29 years, and only 27% had a trend toward improvement in photosensitivity. Involvement of eyes and nonexposed skin was reported in 62.2% and 18.9% of subjects, respectively. Physical examination revealed involvement of the face (64.9%), lip (32.4%), ear (13.5%), and dorsal aspect of the hand (24.3%). HLA-DRB1*14 was present in 51.2% of subjects and 26.2% of controls (P =.022, odds ratio = 2.975). This is a previously unreported HLA association.

CONCLUSION

AP in the Inuit is a seasonal, pruritic photodermatitis, often commencing in adulthood and worsening over time. A novel association with HLA-DRB1*14 has been discovered. Overall, this novel HLA association, the absence of HLA associations previously reported in non-Inuit populations, and clinical distinguishing features support the concept that AP in the Inuit may have a distinct immunopathogenic basis that translates into a different phenotype. It also raises the question of whether AP in the Inuit is a distinct photosensitivity disorder specific to this group that has been genetically isolated because of geographic and cultural seclusion.

Effectors of inflammation in actinic prurigo

BACKGROUND

Actinic prurigo is a specific familial photodermatosis of uncertain pathogenesis.

OBJECTIVE

Our purpose was to investigate the immunohistologic presentation of actinic prurigo to explore the involved pathomechanisms.

METHODS

The present immunohistochemical study was performed on biopsy specimens from 20 Mexican patients presenting with a severe and perennial form of the disease.

RESULTS

The dense inflammatory infiltrate was composed predominantly of helper T type 1 lymphocytes admixed with scattered B-cell lymphoid follicles and numerous dermal dendrocytes. Keratinocytes contained abundant tumor necrosis factor-alpha and calprotectin.

CONCLUSION

In subjects genetically predisposed to actinic prurigo, ultraviolet light may trigger excessive tumor necrosis factor-alpha production by keratinocytes whose sustained release in turn exerts its proinflammatory activity and deleterious epidermal effects. Such a cascade of events is in line with the therapeutic benefit already reported when thalidomide is used to treat actinic prurigo.

[T and B clonal populations in actinic prurigo, a photodermatosis]

Actinic prurigo (AP) is a chronic photodermatosis in which genetic and immunological factors has been implicated in the pathogenesis of the disease. This work was designed to investigate the existence of clonal populations of T and B lymphocytes in lesions of the labial mucosa and conjunctiva of patients with actinic prurigo. Genomic DNA of three patients with actinic prurigo and controls were analyzed in Southern blots using DNA molecular probes for the b subunit of the T-cell receptor for antigen (TCR beta) and for the heavy chain of immunoglobulin genes (lg-JH). Clonal rearrangements of T-cell receptor genes were detected in biopsy samples taken from the labial mucosa of two patients and of immunoglobulin genes in DNA extracted from the conjunctiva of a different patient. The presence of distinct clonal T or B lymphocyte populations in patients with actinic prurigo indicates that the immune system may play a relevant role in the pathogenesis of the disease.

Genetic modeling of abnormal photosensitivity in families with polymorphic light eruption and actinic prurigo

Actinic prurigo and polymorphic light eruption are two of the so-called idiopathic photodermatoses, resulting from abnormal cutaneous responses to ultraviolet radiation (photosensitivity). Whereas they are clinically distinct in most cases, there are sufficient similarities between them to suggest they may be related conditions. To take this further, we examined the prevalence of polymorphic light eruption in families ascertained through actinic prurigo probands, as evidence of a shared pathogenesis. We then determined the heritability of photosensitivity in 420 individuals from families ascertained through polymorphic light eruption and actinic prurigo probands using segregation analysis. Across 58 pedigrees the prevalence of photosensitivity in first-degree relatives was 20.9% compared with a population prevalence of 13.6%, giving a relative risk of 1.5 (confidence interval 1.15-2.0) and providing evidence of clustering within families. The prevalence of photosensitivity (predominantly polymorphic light eruption) in relatives of actinic prurigo probands was 23.7%, with a relative risk of 1.74 (confidence interval 1.24-2.36). Modeling for polymorphic light eruption across all pedigrees revealed a strong genetic component with polymorphic light eruption showing a dominant mixed mode of inheritance. The model parameters estimate that 72% of the U.K. population carry a low penetrance polymorphic light eruption susceptibility allele, but that among this highly prevalent genotype only 24% of susceptible females and 13% of susceptible males will have polymorphic light eruption. Expression of polymorphic light eruption in genetically susceptible individuals (intergenotype variance) is determined in large part by a polygenic component, with an important additional environmental component. In summary, this study provides clear evidence that polymorphic light eruption is an inherited condition. It also suggests that polymorphic light eruption and actinic prurigo share a common genetic background, supporting the view that actinic prurigo may represent a human leukocyte antigen-restricted subset of polymorphic light eruption.

[Actinic prurigo. An assessment of current status]

BACKGROUND AND OBJECTIVE

Actinic prurigo (AP) is a hereditary photodermatoses with typical symptoms and is quite common in North- and South-America. The key genetic factor appears to be a Native American background. In Europeans this type of AP is extremely rare; some dispute if this disease exists in Caucasians. Some newer publications postulate that these patients share HLA markers with the Native Americans. The most important differential diagnosis for AP is polymorphic light eruption which can be excluded relatively accurately by the clinical picture, typical histology and HLA pattern.

PATIENTS/METHODS

The case of a female patient of Mayan ancestry living in Germany is presented.

CONCLUSIONS

Since in literature sometimes cases from Europe are diagnosed as AP this is a problem of naming the disease. It would be helpful to integrate the terms hereditary or hereditaria into the name of the disease in indians.

Major gene segregation of actinic prurigo among North American Indians in Saskatchewan

Actinic prurigo is an idiopathic, familial photodermatosis seen especially in American Indians. Segregation analysis was performed on 12 Saskatchewan pedigrees with American Indian ancestry, comprising a total of 1,148 individuals, ascertained via probands diagnosed with actinic prurigo. Although a high degree of familial aggregation has been noted in the past and dominant inheritance has been suggested, no formal segregation analysis has been attempted. Actinic prurigo has a variable age of onset and, therefore, age at the time of censoring must be taken into account in the analysis. However, as these ages of 57% of the unaffected individuals were missing, an algorithm was devised to impute the missing ages from known birth years in the family based on the age differences among relatives and spouses. Using these imputed ages, simple dominant inheritance with incomplete penetrance and a single age of onset distribution was found. The method for imputing the ages at examination was evaluated, as was the correction for ascertainment, by using alternative methods and comparing the results. Regardless of the method used, a dominant mode of inheritance without any multifactorial component remained the best hypothesis.

Actinic prurigo and polymorphic light eruption: common pathogenesis and the importance of HLA-DR4/DRB1*0407

Actinic prurigo (AP) and polymorphic light eruption (PLE) both belong to the group of idiopathic photodermatoses, but it remains controversial whether AP is a distinct photodermatosis or a variant of PLE. The aim of this study, by collecting data from 119 patients with features of these disorders, was to establish whether specific criteria could be used to distinguish AP from PLE prospectively. We found that presence of the eruption on both exposed and covered sites, its occurrence in winter, persistence of lesions beyond 4 weeks, mucosal and conjunctival involvement, excoriation and scarring of the skin were important features of AP which were not typical of PLE. On this basis, confident clinical diagnoses could be reached in 103 of 119 patients (87%), 57 with AP and 46 with PLE, supported by phototesting and negative lupus serology. HLA typing subsequently confirmed the strong association (90%) between AP and the DR4 allele, in particular with the rare subtype DRB1*0407 which was present in 60% of these patients. No HLA association was found in PLE. In the 16 remaining cases, however, clinical overlap meant that no definite diagnosis could be made; these patients were notionally described as having persistent PLE (PPLE). Demographic and HLA data in this group suggested that PPLE was perhaps most appropriately grouped with PLE. In addition to those patients who were difficult to classify, 35% of our typical AP patients also described clinical progression from PLE to AP, AP to PLE or coexistence of both AP and PLE. In conclusion, our study suggests that while AP and PLE are clinically distinct conditions in most cases, they may perhaps share a common pathophysiological basis. The AP phenotype may be determined by HLA and perhaps other factors in patients otherwise predisposed to PLE.

[Actinic prurigo of childhood. 3 familial cases associated with HLA-DR 0407]

BACKGROUND

Actinic prurigo, as idiopathic skin reaction involving light-exposed areas, was first described in American Indians. Actinic prurigo was early considered to be a particular form at polymorphous phototoxicity, but can be identified as a specific entity on the bases of clinical features and epidemiological characteristics.

CASE REPORTS

Three children in the same family developed photosensitive reactions early in childhood with characteristic polymorphous and persistent eczema-like or papulo-nodular pruriginous lesions which predominated in light-exposed areas and appeared several hours after exposure to sun. The lesions persisted during the winter season. The lesions followed a chronic course but tended to improve at puberty. Clinical laboratory tests, serum and urine porphyrin levels and antinuclear factors were normal. Histology and photobiology explorations gave non-specific results.

DISCUSSION

These observations have three points in common with actinic prurigo observed in American Indians. HLA typing showed that our three patients, as in white patients in Great Britain, had a significant association with a specific HLA DR1 subtype: DRB1*0407. This DRB1*0407 alleles could play a role in initiating the immune response to a light-induced peptide antigen. This particular genetic predisposition, if confirmed in other studies, would be an additional argument for distinguishing actinic prurigo as a specific polymorphous phototoxicity entity.

Further evidence of the role of HLA-DR4 in the genetic susceptibility to actinic prurigo

BACKGROUND

Actinic prurigo (AP) is triggered by sun exposure. Its prevalence in Mexicans seems to be particularly high, which suggests a genetic susceptibility.

OBJECTIVE

Our purpose was to determine the role of major histocompatibility complex (MHC) genes in the genetic susceptibility to AP.

METHODS

Fifty-six Mexican Mestizo patients with AP underwent serologic typing for HLA class I and class II antigens. Class II MHC genes were also studied by DNA analysis. Findings in patients were compared with 100 ethnically matched healthy controls.

RESULTS

We found that 92.8% of patients with AP were HLA-DR4 positive (corrected p = 0.002; odds ratio [OR] = 10.1). The class I antigens HLA-A28 and HLA-B39 (B16) were also significantly increased (p < or = 0.000001, OR = 20.9 and p = 0.0001, OR = 6.7, respectively) compared with normal controls. Allele-specific oligonucleotide DR4 subtyping showed that 80.7% of HLA-DR4+ patients with AP were also positive for the DRB1*0407 allele.

CONCLUSION

These results confirm the role of HLA-DR4 (DRB1*0407) in the genetic susceptibility to AP and raise the possibility of a role for class I MHC antigens HLA-A28 and B16 in Mexican patients.

Profile of cytokine mRNA expression in spontaneous and UV-induced skin lesions from actinic prurigo patients

BACKGROUND

Actinic prurigo (AP) appears to be an immune-mediated disease triggered by exposure to ultraviolet light (UV).

OBJECTIVE

To assess the profile of cytokine production in skin lesions from AP patients.

METHODS

The cytokine production (IL-1 beta, IL-2, IL-4, IL-6, IL-10, IL-13, TNF-alpha, IFN-tau, and TGF-beta) in skin biopsies from 12 AP lesions was determined by a semiquantitative coupled reverse transcription-polymerase chain reaction.

RESULTS

We found expression of TGF-beta and IL-13 genes in most AP skin lesions; IL-1 beta, IL-6, TNF-alpha, IFN-tau, and IL-10 were detected in some of these specimens. However, the levels of expression of all cytokines studied were not significantly different in AP skin lesions compared to nonlesional skin.

CONCLUSIONS

TGF-beta and IL-13 might have a key role in both the inflammatory phenomenon and absence of significant expression of most cytokines in AP skin. The cytokine production in AP skin resembles that observed in rheumatoid synovium, a paucity in cytokine expression despite the presence of infiltrating activated mononuclear cells.

Hereditary polymorphic light eruption of American Indians: occurrence in non-Indians with polymorphic light eruption

BACKGROUND

Hereditary polymorphic light eruption (HPLE) occurs unique ly in the American Indian and Inuit and exhibits autosomal dominant transmission. Because the cutaneous expression of HPLE resembles that of polymorphic light eruption (PLE) and because many non-Indians in the United States have American Indian heritage, some instances of PLE may actually be HPLE.

OBJECTIVE

Our purpose was to determine whether non-Indian patients with PLE have characteristics suggestive of HPLE.

METHODS

We surveyed in Nebraska 25 European-Caucasian and 36 African-American patients with PLE for American Indian heritage and photosensitive relatives. Nonphotosensitive subjects (52 Caucasians and 40 African Americans) were surveyed for American Indian heritage.

RESULTS

American Indian heritage occurred in 11 Caucasian patients (44%); of those, seven (64%) had photosensitive relatives. Likewise, 29 African Americans (81%) had American Indian heritage; 19 (66%) of those had photosensitive relatives. American Indian heritage occurred in 10 Caucasian control subjects (19%) and in 34 African-American control subjects (85%).

CONCLUSION

If American Indian heritage and a family history of photosensitivity are definitive for HPLE, seven (28%) of our Caucasian patients and 19 (53%) of our African-American patients have HPLE rather than PLE. We urge physicians who suspect PLE in non-Indians to ask about American Indian heritage and photosensitive relatives and to screen their present patients with PLE for such characteristics.

Follicular cheilitis. A distinctive histopathologic finding in actinic prurigo

Actinic prurigo (AP), a chronic skin disease caused by an abnormal reaction to sunlight, is commonly associated with cheilitis and conjunctivitis. Characteristic ethnic, genetic, environmental (occurs at high altitudes, above 1,500 m), clinical, and histopathologic features have been reported. AP occurs in American Indians of Canada and the United States and most commonly in Latin American countries, where Mestizos (mixed ancestry) are predominantly affected. The present study investigates AP involving the lips, where it is characterized by a dense lymphocytic infiltrate, often with well-formed lymphoid follicles; the latter feature we refer to as "follicular cheilitis" (FC). The histopathologic findings of FC are characteristic of and helpful in diagnosing actinic prurigo involving the lips.

Actinic prurigo among the Chimila Indians in Colombia: HLA studies

The Chimila, a Colombian Amerindian group that lives at a low altitude, have a high incidence of actinic prurigo. We present the human lymphocyte antigen (HLA) findings of 43 Chimilas with the disease and of 62 control subjects and show an association of actinic prurigo with the Cw4 antigen.

HLA typing in actinic prurigo

Thirty-two actinic prurigo patients of Cree ancestry underwent human lymphocyte antigen (HLA) typing and were compared with 32 control subjects of Cree ancestry. We found a significantly increased frequency of HLA-A24 and Cw4 antigens and a significant decrease in the frequency of the A3 antigen in actinic prurigo patients. These HLA associations may be helpful in determining whether actinic prurigo is a distinct disease or a variant of polymorphous light eruption.

Actinic prurigo of the lower lip. Review of the literature and report of five cases

Actinic prurigo (AP) is a chronic, familial, photodermatitis that primarily affects American Indians. It is more prevalent in young females and may be evident clinically as a pruritic lower lip cheilitis that typically does not respond to conventional therapy. Other clinical features associated with AP include conjunctivitis, alopecia of the eyebrows, and formation of pterygia. The histologic features of AP have been described as nonspecific. We are presenting five cases of AP in which the major clinical manifestation was a pruritic, unsightly lower lip cheilitis. All of our patients were American Indians. Three patients were from the same family. The youngest patient was 10 years old and the oldest was 69 years old. All five cases were characterized histologically by numerous germinal centers within the lamina propria and a dense perivascular plasma cell infiltrate. In four of the five cases, there was a moderate to dense infiltrate of eosinophils. All five patients had been generally unresponsive to conventional therapy. With the exception of the youngest patient, all had had the disease for at least several years. One patient, now deceased, had the lower lip lesion surgically removed for cosmetic reasons. To our knowledge, this is the first report in the dental literature that describes the clinical and histologic features of AP of lower lip.

Actinic prurigo

Actinic prurigo is a chronic photodermatitis found predominantly in North American Indians. Other terms have been used to describe similar cases in Central and South America and in Europe. Relatively little has been written about this condition in the English literature, and confusion exists over whether this is a form of polymorphic light eruption. Actinic prurigo can be considered a unique variant of polymorphic light eruption; however, we believe that certain differences help to distinguish actinic prurigo as a separate disease entity. Herein we report three cases of this disease and review the related literature. Characteristic clinical features include prurigolike papules and cheilitis. Pruritus is the predominant symptom, and a familial tendency and an early age at onset are usually noted. Results of karyotyping and analysis of sister chromatid exchanges were normal in two of our patients so tested. Skin testing for photosensitivity has yielded inconsistent results, and use of light testing for diagnosing actinic prurigo does not seem to be a predictable procedure. Actinic prurigo is a chronic disease that often is refractory to therapy.