Transcriptional profiling of rare acantholytic disorders suggests common mechanisms of pathogenesis.

Darier, Hailey-Hailey, and Grover diseases are rare acantholytic skin diseases. While these diseases have different underlying causes, they share defects in cell-cell adhesion in the epidermis and desmosome organization. To better understand the underlying mechanisms leading to disease in these conditions, we performed RNA-seq on lesional skin samples from patients. The transcriptomic profiles of Darier, Hailey-Hailey, and Grover diseases were found to share a remarkable overlap, which did not extend to other common inflammatory skin diseases. Analysis of enriched pathways showed a shared increase in keratinocyte differentiation, and a decrease in cell adhesion and actin organization pathways in Darier, Hailey-Hailey, and Grover diseases. Direct comparison to atopic dermatitis and psoriasis showed that the downregulation in actin organization pathways was a unique feature in the acantholytic skin diseases. Furthermore, upstream regulator analysis suggested that a decrease in SRF/MRTF activity was responsible for the downregulation of actin organization pathways. Staining for MRTFA in lesional skin samples showed a decrease in nuclear MRTFA in patient skin compared with normal skin. These findings highlight the significant level of similarity in the transcriptome of Darier, Hailey-Hailey, and Grover diseases, and identify decreases in actin organization pathways as a unique signature present in these conditions.

Association of Somatic ATP2A2 Damaging Variants With Grover Disease.

Importance: Grover disease (GD), a truncal eruption that typically occurs in older individuals, is exacerbated by sweating, irradiation, cancers, medications, kidney failure, and organ transplantation. The pathobiology of GD remains unknown. Objective: To determine if damaging somatic single-nucleotide variants (SNVs) are associated with GD. Design, Setting, and Participants: In this retrospective case series, we identified consecutive patients from a dermatopathology archive over a 4-year period (January 2007 to December 2011) who had 1 biopsy with a clinical diagnosis of GD confirmed via histopathologic findings and another non-GD biopsy. Participant DNA was extracted from both biopsy tissues and sequenced to high depth with a 51-gene panel to screen for SNVs in genes previously associated with acantholysis and Mendelian disorders of cornification. Analysis took place between 2021 and 2023. Main Outcomes and Measures: Comparative analysis of sequencing data from paired GD and control tissue was employed to identify SNVs predicted to affect gene function, which were exclusive to, or highly enriched in, GD tissue. Results: Overall, 12 of 15 cases of GD (12 men and 3 women; mean [SD] age, 68.3 [10.0] years) were associated with C>T or G>A ATP2A2 SNVs in GD tissue; all were predicted to be highly damaging via combined annotation dependent depletion (CADD) scores, and 4 were previously associated with Darier disease. In 9 cases (75%), the GD-associated ATP2A2 SNV was absent from control tissue DNA, and in 3 cases (25%), ATP2A2 SNVs were enriched 4- to 22-fold in GD vs control tissue. Conclusions and Relevance: In this case series study of 15 patients, damaging somatic ATP2A2 SNVs were associated with GD. This discovery expands the spectrum of acantholytic disorders associated with ATP2A2 SNVs and highlights the role of somatic variation in acquired disorders.

Disseminated papular variant of Dowling-Degos disease: Histopathological features in POGLUT1 mutation.

Dowling-Degos disease is a rare benign genodermatosis. It is characterized by lentiginous hyperpigmentation and reddish-brown papules and plaques. The flexor sides and intertrigines are often affected, but the clinical appearance may vary. Mutations in different genes are responsible for the clinical manifestation. While mutations in the keratin 5 (KRT5) gene favor a reticular distribution pattern, mutations in the POGLUT1 gene lead to a disseminated, papular clinical picture. Acantholytic variants of Dowling-Degos disease have historically been referred to as Galli-Galli disease, but our case study shows that the histopathological changes can vary even within a single patient. To date, no standardized therapy concept exists. The main focus is on keratolytic measures, with varying response. New therapeutic approaches using laser technology appear to be a promising treatment option.

Dowling-Degos disease: a review.

Dowling-Degos disease is a rare autosomal dominant genodermatosis. It is characterized by acquired reticulate hyperpigmentation over the flexures, comedone-like follicular papules, and pitted perioral scars that usually develop during adulthood. Mutations in genes affecting melanosome transfer, and melanocyte and keratinocyte differentiation have been implicated in the pathogenesis of this disease. These genes include KRT5, POFUT1, POGLUT1 and, most recently, PSENEN. Dowling-Degos disease can be found in isolation or with other associated findings, most notably hidradenitis suppurativa. This condition belongs to a spectrum of conditions that all result in reticulate hyperpigmentation that at times are hard to distinguish from each other. The most closely linked entity is Galli-Galli, which is clinically indistinguishable from Dowling-Degos disease and can only be distinguished by the presence of acantholysis on microscopy. Unfortunately, Dowling-Degos disease is generally progressive and recalcitrant to treatment.

ATP2A2 SINE Insertion in an Irish Terrier with Darier Disease and Associated Infundibular Cyst Formation.

A 4-month-old female Irish Terrier presented with a well demarcated ulcerative and crusting lesion in the right ear canal. Histological analysis revealed epidermal hyperplasia with severe acantholysis affecting all suprabasal layers of the epidermis, which prompted a presumptive diagnosis of canine Darier disease. The lesion was successfully treated by repeated laser ablation of the affected epidermis. Over the course of three years, the dog additionally developed three dermal nodules of up to 4 cm in diameter that were excised and healed without complications. Histology of the excised tissue revealed multiple infundibular cysts extending from the upper dermis to the subcutis. The cysts were lined by squamous epithelium, which presented with abundant acantholysis of suprabasal keratinocytes. Infundibular cysts represent a novel finding not previously reported in Darier patients. Whole genome sequencing of the affected dog was performed, and the functional candidate genes for Darier disease (ATP2A2) and Hailey-Hailey disease (ATP2C1) were investigated. The analysis revealed a heterozygous SINE insertion into the ATP2A2 gene, at the end of intron 14, close to the boundary of exon 15. Analysis of the ATP2A2 mRNA from skin of the affected dog demonstrated a splicing defect and marked allelic imbalance, suggesting nonsense-mediated decay of the resulting aberrant transcripts. As Darier disease in humans is caused by haploinsufficiency of ATP2A2, our genetic findings are in agreement with the clinical and histopathological data and support the diagnosis of canine Darier disease.

The Differentiation-Associated Keratinocyte Protein Cornifelin Contributes to Cell-Cell Adhesion of Epidermal and Mucosal Keratinocytes.

Cornifelin (CNFN) has been identified as a protein component of epidermal corneocytes. Here, we investigated the tissue distribution of CNFN and potential consequences of CNFN deficiency on epithelial function in in vitro models of human skin and oral mucosa. Our detailed bioinformatics and immunostaining analysis revealed that CNFN is not only expressed in human epidermis but also in noncornifying oral mucosa. In normal epidermis, CNFN was confined to the upper granular layer and the stratum corneum. By contrast, in both partly cornifying and noncornifying oral mucosa, CNFN was expressed in a cell membrane-associated pattern over several suprabasal layers. Small interfering RNA-mediated knockdown of CNFN in epidermal keratinocytes (KCs) was associated with only subtle alterations of the overall epidermal architecture in skin models in vitro but led to altered morphology of corneodesmosomes, as detected by electron microscopy. Using dispase treatment followed by mechanical stress, epithelial sheets of CNFN-deficient epidermal KCs were easily disrupted, whereas their CNFN-competent counterparts remained intact. In contrast to the epidermal KCs, CNFN knockdown in oral KCs had a more severe effect and caused pronounced acantholysis in organotypic models of oral mucosa. Together, these findings indicate that CNFN is a structural component of the cell adhesion system of differentiated KCs in both epidermis and oral mucosa.

Heterozygous frameshift mutation in keratin 5 in a family with Galli-Galli disease.

BACKGROUND: Reticulate pigmentary disorders include the rare autosomal dominant Galli-Galli disease (GGD) and Dowling-Degos disease (DDD). Clinical diagnosis between some of the subtypes can be difficult due to a degree of overlap between clinical features, therefore analysis at the molecular level may be necessary to confirm the diagnosis. OBJECTIVES: To identify the underlying genetic defect in a 48-year-old Asian-American woman with a clinical diagnosis of GGD. METHODS: Histological analysis was performed on a skin biopsy using haematoxylin-eosin staining. KRT5 (the gene encoding keratin 5) was amplified from genomic DNA and directly sequenced. RESULTS: The patient had a history of pruritus and hyperpigmented erythematous macules and thin papules along the flexor surfaces of her arms, her upper back and neck, axillae and inframammary areas. Hypopigmented macules were seen among the hyperpigmentation. A heterozygous 1-bp insertion mutation in KRT5 (c.38dupG; p.Ser14GlnfsTer3) was identified in the proband. This mutation occurs within the head domain of the keratin 5 protein leading to a frameshift and premature stop codon. CONCLUSIONS: From the histological findings and mutation analysis the individual was identified as having GGD due to haploinsufficiency of keratin 5.

Desmosomal adhesion and pemphigus vulgaris: the first half of the story.

Pemphigus vulgaris (PV) is a paradigm of autoimmune disease affecting intercellular adhesion. The mechanisms that lead to cell-cell detachment (acantholysis) have crucial therapeutic implications and are currently undergoing major scrutiny. The first part of this review focuses on the classical view of the pathogenesis of PV, which is dominated by the cell adhesion molecules of the desmosome, namely desmogleins (Dsgs). Cloning of the DSG3 gene, generation DSG3 knock-out mice and isolation of monoclonal anti-Dsg3 IgG have aided to clarify the pathogenic mechanisms of PV, which are in part dependent on the fate of desmosomal molecules. These include perturbation of the desmosomal network at the transcriptional, translational, and interaction level, kinase activation, proteinase-mediated degradation, and hyper-adhesion. By the use of PV models, translational research has in turn helped shed light into the basic structure, function, and dynamics of assembly of desmosomal cadherins. The combined efforts of basic and applied research has resulted in tremendous advance into the understanding of epidermal adhesion and helped debunk old myths on the supposedly unique role of desmogleins in the mechanisms of cell-cell detachment in PV.

[Antidesmoglein antibodies in a patient with Hailey-Hailey disease]. / Détection d'anticorps antidesmogléines circulants chez un patient atteint de maladie de Hailey-Hailey.

BACKGROUND: Hailey-Hailey disease (HHD) is a rare hereditary disease in which the genetic defect is characterized by mutation in the ATP2C1 gene coding for a transmembrane calcium pump. It is generally considered a non-immunologic acantholytic dermatosis in which direct and indirect immunofluorescence studies are negative, unlike in autoimmune pemphigus. PATIENTS AND METHODS: We describe a case of HHD associated with antidesmoglein antibodies in a 53-year-old woman. The clinical symptoms and histology were typical of HHD. Antidesmoglein antibody tests were positive on several occasions and a difference was found between the two types of Elisa test performed (positive with the MBL kit, negative with the Euroimmun kit). DISCUSSION: The positive result for desmoglein antibodies could be due to unmasking of antigens by the mechanism of acantholysis. The specificity of the main desmoglein Elisa tests also requires discussion.

Grover's disease following multiple bilateral Blaschko lines: a rare clinical presentation with genetic and electron microscopic analyses.

Grover's disease is an acquired dermatosis of unknown cause histopathologically characterized by the presence of acantholysis. We report an 83-year-old Japanese man who showed multiple pruritic papular lesions distributed bilaterally along Blaschko lines, necessitating the exclusion of segmental Darier's disease. No mutations in ATP2A2, ATP2C1 or keratin 5 genes were found both in the lesional skin and in peripheral leukocytes, suggesting that putative pathogenesis of Grover's disease is distinct from those of other acantholytic dermatoses. Electron microscopy revealed poorly developed tonofibrils in the basal cells, and the structure of desmosomes appeared normal, with an increase in the number of desmosomes in the spinous layer, indicating compensation of defective desmosomal function. Impairment of desmosomal plaque proteins linking tonofilaments to desmosomal cadherins may thus account for acantholysis. The unusual bilateral mosaic arrangement in our patient may offer valuable clues to the genetic basis of Grover's disease.

[Galli-Galli disease. Clinical and histopathological investigation using a case series of 18 patients]. / Morbus Galli-Galli. Klinische und histopathologische Untersuchung anhand einer Fallserie von 18 Patienten.

Galli-Galli disease, a rare genodermatosis belonging to the spectrum of reticulate pigment dermatoses, is classified as an acantholytic variant of Dowling-Degos disease on the basis of its characteristic clinical and histological findings. In the context of this case series, Galli-Galli disease is characterized in detail based on the clinical and histopathological evaluation of 18 patients. The disease pattern is discussed in view of the current literature. In addition, a classification into two clinical subtypes is made and a genotype/phenotype correlation with mutations in the keratin 5 (KRT5) gene is established.

Identification a novel missense mutation p.R761L in Chinese patients with Darier's disease.

Darier's disease (DD, MIM 124200) is an autosomal dominant inherited disease. It is usually present in teenagers or adults with multiple keratotic papules or plaques in seborrheic areas. Pathogenic mutations in the ATP2A2 gene have been identified. It encodes the sarcoplasmic or endoplasmic reticulum Ca(2+) ATPase isoform 2 (SERCA2). Polymerase chain reaction and direct sequencing of the full coding sequence of ATP2A2 gene were performed to identify the mutation in this family. In this report, we identified a novel mutation of ATP2A2 gene in a Chinese family with DD. It is a novel heterozygous nucleotide G --> T transition at position 2,282 in exon 15 of the ATP2A2 gene. Our study expands the database on the ATP2A2 gene mutations in DD.

Systematic mutation screening of KRT5 supports the hypothesis that Galli-Galli disease is a variant of Dowling-Degos disease.

BACKGROUND: Galli-Galli disease (GGD) is a rare genodermatosis. Its clinical presentation is identical to that of Dowling-Degos disease (DDD), but the presence of the histopathological feature of acantholysis in GGD is thought to distinguish the two disorders. Mutations in the keratin 5 gene (KRT5) have been identified in the majority of patients with DDD and in a small number of patients with GGD. OBJECTIVES: To provide further support for the hypothesis that GGD is merely a variant of DDD, and to examine whether acantholysis is genuinely rare in DDD or rather a common but under-reported histological feature of DDD. METHODS: We conducted the first systematic mutational investigation of patients with GGD and re-examined the histopathology of patients previously assigned a diagnosis of DDD. For the mutational investigation, KRT5 was sequenced in seven unrelated patients with clinically and histopathologically confirmed GGD. In addition, the histopathological findings of six patients with DDD were re-evaluated. RESULTS: The mutation c.418dupA was found in five patients with GGD. The typical histopathological features of GGD were identified in six patients who had previously been assigned a diagnosis of DDD. CONCLUSIONS: We found further evidence to suggest that GGD is indeed a variant of DDD and not a distinct disease entity. Two facts in particular support this conclusion: the same KRT5 mutation was found in patients with GGD and in patients with DDD, and acantholysis seems to be present in a large number of patients who had previously been assigned a diagnosis of DDD.