Recent Advances in Clinical Research on Rare Intractable Hereditary Skin Diseases in Japan

Our Research Group for Rare and Intractable Skin Diseases operates within the Project for Research on Intractable Diseases of the Ministry of Health, Labour, and Welfare of Japan and is conducting research on eight rare intractable skin diseases. Five of these are monogenic disorders (epidermolysis bullosa, congenital ichthyoses, oculocutaneous albinism, pseudoxanthoma elasticum, and hereditary angioedema), and for a sixth [generalized pustular psoriasis (GPP)], genetic predisposing factors are important. This review introduces our activities for raising public awareness of these six intractable hereditary skin diseases and summarizes our recent achievements in clarifying the situation of medical treatments for these diseases in Japan. We note our current progress in elucidating the pathogeneses of these diseases and in developing new treatment methods, and we discuss our progress in establishing clinical practice guidelines. A nationwide survey on epidermolysis bullosa and a clinical survey on congenital ichthyoses are progressing. The Angioedema Activity Score and the Angioedema Quality-of-Life Questionnaire, the latter of which is a quality-of-life evaluation tool, have been established for hereditary angioedema. Registries of patients with oculocutaneous albinism and pseudoxanthoma elasticum have been created, and the registry for the latter has achieved its target of 170 cases. For GPP, the results of our survey on clinical practice were published in 2021. Information regarding all six of these hereditary skin diseases has been disseminated to academic societies, medical professionals, patients, and the general public.

Monogenic causes of pigmentary mosaicism

Pigmentary mosaicism of the Ito type, also known as hypomelanosis of Ito, is a neurocutaneous syndrome considered to be predominantly caused by somatic chromosomal mosaicism. However, a few monogenic causes of pigmentary mosaicism have been recently reported. Eleven unrelated individuals with pigmentary mosaicism (mostly hypopigmented skin) were recruited for this study. Skin punch biopsies of the probands and trio-based blood samples (from probands and both biological parents) were collected, and genomic DNA was extracted and analyzed by exome sequencing. In all patients, plausible monogenic causes were detected with somatic and germline variants identified in five and six patients, respectively. Among the somatic variants, four patients had MTOR variant (36%) and another had an RHOA variant. De novo germline variants in USP9X, TFE3, and KCNQ5 were detected in two, one, and one patients, respectively. A maternally inherited PHF6 variant was detected in one patient with hyperpigmented skin. Compound heterozygous GTF3C5 variants were highlighted as strong candidates in the remaining patient. Exome sequencing, using patients' blood and skin samples is highly recommended as the first choice for detecting causative genetic variants of pigmentary mosaicism.

Current topics in Epidermolysis bullosa: Pathophysiology and therapeutic challenges

Epidermolysis bullosa (EB) is a group of inherited skin and mucosal fragility disorders resulting from mutations in genes encoding basement membrane zone (BMZ) components or proteins that maintain the integrity of BMZ and adjacent keratinocytes. More than 30 years have passed since the first causative gene for EB was identified, and over 40 genes are now known to be responsible for the protean collection of mechanobullous diseases included under the umbrella term of EB. Through the elucidation of disease mechanisms using human skin samples, animal models, and cultured cells, we have now reached the stage of developing more effective therapeutics for EB. This review will initially focus on what is known about blister wound healing in EB, since recent and emerging basic science data are very relevant to clinical translation and therapeutic strategies for patients. We then place these studies in the context of the latest information on gene therapy, read-through therapy, and cell therapy that provide optimism for improved clinical management of people living with EB.

Analysis of clinical characteristics, prognosis and antibody pathogenicity of pemphigus patients positive for anti-desmoglein IgG autoantibodies in remission: a retrospective cohort study

BACKGROUND

The detection of serum anti-desmoglein (Dsg) IgG autoantibodies has been reported to be useful for assessment of disease activity in pemphigus. However, previous studies have reported that anti-Dsg autoantibodies remain detectable in some patients without active pemphigus lesions.

OBJECTIVES

To investigate the clinical characteristics and antibody pathogenicity of pemphigus patients positive for anti-Dsg IgG autoantibodies in remission.

METHODS

We retrospectively investigated pemphigus patients with a history of clinical remission who visited the Department of Dermatology of Keio University during 2019 and 2020. The antibody pathogenicity was assessed by bead aggregation assay.

RESULTS

When patients were recognized as having entered remission (PDAI = 0 and PSL ≦ 10 mg/day for 2 months), serum autoantibodies against Dsg were detected in 72 of 132 patients (54.5%, positive group; PG), but were not detected in 60 patients (45.5%, negative group; NG). Anti-Dsg antibody titres in remission declined from the active phase in 33 patients in the PG for whom data were available. There were no differences in the chance of reducing PSL to 5 mg/day (P = 0.885) and rate of relapse (P = 0.279) between PG and NG, but fewer patients in PG discontinued corticosteroids (P = 0.004). The ability of patients' sera to block aggregation of Dsg/desmocollin beads was significantly reduced in remission compared to the active phase. However, our results revealed that whole sera in remission still had pathogenic activity in seven of nine patients, and the approximately equal amounts of anti-Dsg antibodies in active phase and remission showed similar pathogenicity.

CONCLUSIONS

This study will provide guidance in cases where autoantibodies are found to be positive in pemphigus patients during remission or steroid reduction.

A multicenter, open-label, uncontrolled, single-arm phase 2 study of tirabrutinib, an oral Bruton's tyrosine kinase inhibitor, in pemphigus

BACKGROUND

The treatment of pemphigus is based on systemic corticosteroid use and adjuvant therapies, but some patients are resistant to conventional therapy. Tirabrutinib is a highly selective oral Bruton's tyrosine kinase inhibitor that may be clinically effective in treating pemphigus by suppressing B-cell signaling.

OBJECTIVE

We investigated the efficacy and safety of tirabrutinib in patients with refractory pemphigus.

METHODS

This was a multicenter, open-label, single-arm phase 2 study of Japanese patients with refractory pemphigus receiving appropriate treatment with an oral corticosteroid and adjuvant therapies. Patients received postprandial oral tirabrutinib 80 mg once daily for 52 weeks. After 16 weeks of tirabrutinib treatment, the corticosteroid dose was tapered to ≤10 mg/day of prednisolone equivalent.

RESULTS

In total, 16 patients were evaluated (mean age, 52.5 years; 50 % male). The complete remission rate after 24 weeks of treatment (primary endpoint) was 18.8 % (3/16; 95 % confidence interval, 6.6 %-43.0 %). By Week 52, eight patients (50.0 %) achieved complete remission and 10 patients (62.5 %) achieved remission. Over 52 weeks of treatment, the mean prednisolone dose decreased from 17.03 to 7.65 mg/day. Incidences of adverse events (AEs) and adverse drug reactions were 87.5 % and 43.8 %, respectively. A relationship with tirabrutinib was ruled out for all serious AEs and Grade ≥3 AEs.

CONCLUSION

Treatment with tirabrutinib enabled remission and reduced oral corticosteroid exposure over time and did not result in any major safety concerns in patients with refractory pemphigus. Thus, oral tirabrutinib may be a new treatment option for patients with refractory pemphigus.

Stratum corneum levels of calprotectin proteins S100A8/A9 correlate with disease activity in psoriasis patients

Psoriasis is an intractable inflammatory skin disorder characterized by scaly erythema and plaques. The Psoriasis Area and Severity Index (PASI) is widely used to score disease severity, but evaluation is subjective, and an objective biomarker would be useful. The stratum corneum (SC), which can be non-invasively harvested, may reflect psoriasis-associated changes in epidermal keratinocytes, such as the upregulation of the calprotectin proteins S100A8 and S100A9. The aim of this study was to examine the availability of S100A8/A9 protein levels in SC as a biomarker of psoriasis disease activity. Fifty-three patients with psoriasis, 30 with psoriasis vulgaris (PsV), and 23 with psoriatic arthritis (PsA) participated. SC cells from lesional and non-lesional skin were collected by tape-stripping. S100A8/A9 levels in serum and in SC were quantified by enzyme-linked immunosorbent assay and compared with PASI score before and after treatment initiation or switching. Atopic dermatitis (AD) patients and disease-free individuals were used as controls. Expression of S100A8/A9 in SC of lesional skin of psoriasis patients was significantly higher than in non-lesional skin or AD skin. There was no significant difference of SC S100A8/A9 levels between PsV and PsA patients. The S100A8/A9 levels in SC of psoriasis patients were significantly positively correlated with the PASI score. When patients' skin lesions cleared (PASI clear) in response to treatment, expression of S100A8/A9 in SC was no longer detectable. S100A8/A9 protein levels in SC may be available as an objective, non-invasive biomarker of psoriasis activity to complement PASI scoring.

Pemphigus Vulgaris and Foliaceus IgG Autoantibodies Directly Block Heterophilic Transinteraction between Desmoglein and Desmocollin

Anti-desmoglein (Dsg) 1 and Dsg3 IgG autoantibodies in pemphigus foliaceus and pemphigus vulgaris cause blisters through loss of desmosomal adhesion. It is controversial whether blister formation is due to direct inhibition of Dsg, intracellular signaling events causing desmosome destabilization, or both. Recent studies show that heterophilic binding between Dsg and desmocollin (Dsc) is the fundamental adhesive unit of desmosomes. To eliminate cellular contributions to potential pathogenicity of pemphigus antibodies, bead assays coated with recombinant Dsg1, Dsc1, Dsg3, or Dsc3 ectodomains were developed. A mixture of Dsg beads and Dsc beads formed large aggregates, confirming that the heterophilic binding is dominant. The pathogenic anti-Dsg1 and anti-Dsg3 mAbs, which bind the transadhesive interface, blocked the aggregation of Dsg1/Dsc1 and Dsg3/Dsc3 beads, respectively, whereas nonpathogenic mAbs did not. All sera tested from eight patients with pemphigus foliaceus and eight patients with mucosal pemphigus vulgaris with active disease inhibited the adhesion of Dsg1/Dsc1 and Dsg3/Dsc3 beads, respectively. When paired sera obtained from seven patients with pemphigus foliaceus and six patients with pemphigus vulgaris in active disease and remission were compared, the former inhibited aggregation better than the latter. These findings strongly suggest that steric hindrance of heterophilic transinteraction between Dsg and Dsc is important for disease pathology in both pemphigus foliaceus and pemphigus vulgaris.

Unusual Bone Lesions with Osteonecrosis Mimicking Bone Metastasis of Squamous Cell Carcinoma in Recessive Dystrophic Epidermolysis Bullosa

Some bone lesions are reported to mimic bone metastasis on imaging tests. Herein, we report a case of a 55-year-old Japanese man who presented with a skin tumor on the left lower extremity. He also had a history of recurrent generalized cutaneous blister and erosion formation since childhood. His skin lesions were diagnosed as cutaneous squamous cell carcinoma complicated by recessive dystrophic epidermolysis bullosa. Magnetic resonance imaging of the left lower extremity detected multiple focal bone lesions mimicking bone metastases in the left femur and tibia. However, bone biopsy revealed that the bone lesions were osteonecrosis without tumor cells. We suggest that cancer-induced osteonecrosis should be included in the differential diagnosis of bone lesions suspected of being metastases on magnetic resonance imaging.

Histopathological and electron microscopic study in dogs with patellar luxation and skin hyperextensibility

Patellar luxation is abnormal displacement of the patella from the femoral trochlear groove. It is seen primarily in small breed dogs and causes pain and limited mobility of the stifle joint. This study aimed to investigate the relationship among patellar luxation, skin extension, and skin collagen fibril diameter. Nine dogs with patellar luxation and five clinically normal dogs were enrolled in the study. We measured the skin extension and investigated the ultrastructure of the skin and patellofemoral ligament by histopathology and transmission electron microscopy. The mean skin extension in dogs with patellar luxation was 18.5 ± 5.5% which is greater than the reference value (14.5%). Mean skin extension in controls was 8.8 ± 1.7% and was within the normal range. In dogs with patellar luxation, histopathology of the skin and patellofemoral ligament showed sparse and unevenly distributed collagen fibers. Transmission electron microscopy identified poorly organized, irregularly shaped, thin collagen fibrils. Collagen fibril thickness in dogs with patellar luxation was significantly less than fibril thickness in controls (P<0.001). There was a significant negative correlation (ρ= −0.863; P<0.001) between skin collagen fibril diameter and skin extension. Skin extension was correlated with patellar luxation and disease severity. Dogs with patellar luxation, joint dysplasia, and hyperextensible skin appear to be pathologically related. This might represent a phenotype of the Ehlers–Danlos syndrome, a hereditary connective tissue disorder in humans.

Splice site mutation in COL7A1 resulting in aberrant in-frame transcripts identified in a case of recessive dystrophic epidermolysis bullosa, pretibial

Dystrophic epidermolysis bullosa (DEB), pretibial, a rare subtype of epidermolysis bullosa (EB), is characterized by recurrent blisters and erosions predominantly on the pretibial region. We report the case of a 60-year-old Japanese woman with persistent blistering eruptions and scar formation on the pretibial region and elbows. Mutational analysis revealed a previously reported c.5797C>T mutation in exon 70 (p.R1933X) and a novel c.6348+1G>A mutation in intron 76 of COL7A1. Reverse transcription polymerase chain reaction revealed that the c.6348+1G>A mutation resulted in the skipping of exon 76 (69 bp) and the retention of intron 76 (75 bp), and both transcripts were in-frame. From these results, we diagnosed the patient as having recessive DEB, pretibial. A review of previously reported mutations in DEB, pretibial, revealed that one-third of DEB, pretibial, cases showed a recessive inheritance pattern, and no case had a combination of premature termination codon (PTC)/PTC mutations. The DEB, pretibial, case described herein is the first reported case of a compound heterozygote with PTC/in-frame mutations. Although no special characteristic features of the mutations were identified, a high diversity of COL7A1 mutations was shown even in DEB, pretibial.

Skin lesions of Birt-Hogg-Dubé syndrome: Clinical and histopathological findings in 31 Japanese patients who presented with pneumothorax and/or multiple lung cysts

BACKGROUND

Birt-Hogg-Dubé syndrome (BHDS) (OMIM #135150) is an autosomal dominant disease, characterized by fibrofolliculomas (FFs) of the skin, pulmonary cysts with/without pneumothorax, and renal tumors. The prevalence of skin manifestations reported for Japanese BHDS patients is lower (<30%) compared with that of Western countries (75∼90%), which appear to be underestimated.

OBJECTIVE

To precisely examine the prevalence of skin lesions with dermoscopy and histopathology with reference to genetic analyses.

METHODS

We studied 31 patients (47.0±13.2years old, range 15-71) consisting of 26 unrelated families consecutively from May 2013 to June 2015 specifically for skin-colored papules on their faces and cervicothoracic regions. Patients initially suspected of BHDS from multiple pulmonary cysts that resulted in pneumothorax (30/31; 96.8%) received dermoscopic examinations and skin biopsies if applicable. The diagnosis of BHDS was established by folliculin (FLCN) genetic testing, and the results were compared to the histopathological findings of FFs or trichodiscomas (TDs).

RESULTS

FLCN germline mutation was demonstrated in 25/26 (96.2%) unrelated families tested and 28/29 patients (96.6%) tested. Skin lesions were recognized in 26/31 patients (83.9%); skin biopsies were performed in 23 patients of whom FFs and/or TDs were histologically demonstrated in 17 (73.9%). Although our study population included patients whose skin manifestations were evaluated prior to or after FLCN genetic testing, skin lesions were clearly prevalent and recognizable irrespective of whether genetic testing was or wasn't done. When examined with dermoscopy, distinct FFs appeared as well-demarcated areas of pallor with central follicular openings in 13 of 15 FF-bearing patients (86.7%); however, those manifestations were not recognized for TD.

CONCLUSIONS

Skin lesions appear to be more prevalent than previously reported (<30% vs.73.9%) in Japanese BHDS patients. Dermoscopy is a useful diagnostic aid for finding FFs.

Experimental Laminin 332 Mucous Membrane Pemphigoid Critically Involves C5aR1 and Reflects Clinical and Immunopathological Characteristics of the Human Disease

Mucous membrane pemphigoid is an autoantibody-mediated disease predominantly affecting the oral cavity, pharynx, and conjunctiva. Conjunctival lesions may lead to impaired vision and, finally, blindness. About 25% of mucous membrane pemphigoid patients generate autoantibodies against the α3 chain of laminin 332 (LAMα3), a structural protein of epidermal/epithelial basement membranes. Here, we established a mouse model by the passive transfer of rabbit IgG against the murine homologs of two immunodominant fragments in adult C57BL/6 mice (mLAMα3). After repeated subcutaneous injections of anti-mLAMα3 IgG erosions and crusts occurred predominantly around the snout, eyes, and on ears. Conjunctival and oral/pharyngeal lesions with subepithelial splitting were found in 80% and 100% of mice, respectively. In contrast, disease development was abrogated in FcRγ chain-deficient mice and markedly reduced in C5aR1-deficient mice. Furthermore, wild-type mice injected with anti-mLAMα3 F(ab')2 were completely protected. Our findings suggest a crucial codominant role of FcRγ and complement activation of the anti-mLAMα3 IgG-induced mouse model of mucous membrane pemphigoid. This model will help further discover the pathomechanisms of this devastating disease. Furthermore, it may be of use to explore the effect of urgently needed more specific anti-inflammatory mediators on mucosal and skin lesions in autoantibody-mediated diseases.

Dermoscopic features of nail psoriasis treated with biologics

Although psoriatic nail lesions are small, they cause considerable discomfort for patients and adversely affect quality of life. Few studies have evaluated the dermoscopic features of psoriatic nails. The aim of this study was to clarify the dermoscopic features of nail psoriasis and identify those that reflect psoriatic activity. During biologic treatment of psoriasis, six patients with psoriatic nails twice underwent dermoscopic examination, with an interval of 17-42 weeks. We used the modified Nail Psoriasis Severity Index score and Psoriasis Area and Severity Index score to identify and assess dermoscopic features. We identified 10 dermoscopic findings, of which disappearance of diffuse scaling of the nail plate, transverse step-like notches and splinter hemorrhages of the nail bed, and appearance of erythematous borders of the onycholytic area were associated with improvement in Psoriasis Area and Severity Index score. Dermoscopy can detect nail changes during psoriasis treatment and should be used to evaluate treatment success.

A scabies outbreak in a diabetic and collagen disease ward: Management and prevention

Scabies is an infection caused by Sarcoptes scabiei. In developed countries, scabies remains an important public health problem in hospitals and care facilities among elderly or immunocompromised patients. There are a number of medical providers who have not experienced scabies and there has been confusion surrounding its management and prevention. Therefore, the aim of the present study was to identify the optimal approach for the management and prevention of scabies. A scabies outbreak occurred between June 2014 and October 2014 in the Toho University School of Medicine, Omori Hospital (Tokyo, Japan), and the current study investigates factors concerning the outbreak, such as disease recognition, diagnostic strategy, medical staff experience and correspondence after the outbreak occurred. Six patients were newly diagnosed with scabies including patients, medical staff and family of the medical staff. An infection control committee was implemented and required a follow-up survey of 181 people (144 patients and 37 medical staff). It took ~4 months to resolve the outbreak. Scabies is highly infectious, and sufficient knowledge is required to care for the patients and prevent the infection of healthy people. In this example, the spread of infection was controlled by prompt action.

Compound heterozygosity for novel splice site mutations of ITGA6 in lethal junctional epidermolysis bullosa with pyloric atresia

Junctional epidermolysis bullosa with pyloric atresia (PA-JEB) is a rare congenital bullous disease with gastrointestinal disturbance that has been associated with mutations in ITGA6 or ITGB4 encoding the α6 or β4 subunit of integrin, respectively. Only six ITGA6 mutations in PA-JEB have been reported while many ITGB4 mutations have been identified, and all the ITGA6 mutations were homozygous. Here, we report a case of lethal type PA-JEB, in which immunofluorescence showed the lack of both α6 and β4 integrins resulting from compound heterozygous splice site mutation in ITGA6, c.387G>T and c.2506-1G>C. Maternal c.387G>T induced the skipping of the entire exon 3 and both exons 3 and 4, resulting in premature termination codon and in-frame deletion, respectively. Paternal c.2506-1G>C caused the skipping of the exon 20 and resulted in in-frame deletion. As a reason why the present case showed lethal phenotype despite the in-frame deletion mutation, rapid degradation of neo-synthesized α6 protein and/or impaired transport of integrin were suggested from previous reports, and the lack of localization of integrin α6β4 to the epidermal basement membrane resulted in skin fragility. Our case expands the variety of integrin α6 mutations in PA-JEB.

Acquired dermal melanocytosis of the face and extremities

Acquired dermal melanocytosis (ADM) is a relatively rare, but well-described disease among adolescent to middle-aged East Asian women, particularly those of Japanese and Chinese descent. Clinically, ADM manifests as multiple punctate and greyish-brown pigmented areas 1-3 mm in diameter occurring on both sides of the forehead and zygomatic region. The subtype of ADM affecting the face and extremities is extremely rare even in East Asian women. We describe three patients with ADM of the face and extremities (ADMFE) and their characteristic clinical features. All patients were Japanese women, and showed multiple greyish-brown pigmentations on both nasal wings and on the extensor surface of the extremities. We found that the clinical features were strikingly uniform, and that a pigmented lesion on the nasal wing can be an important clue to distinguish ADMFE from other hyperpigmented diseases of the hands and feet. One patient was treated with Q-switched ruby laser with excellent outcome. Increased awareness of ADMFE can lead to earlier diagnosis and potential treatment.

Radiosensitive Hematopoietic Cells Determine the Extent of Skin Inflammation in Experimental Epidermolysis Bullosa Acquisita

Animal models have enhanced our understanding of the pathogenesis of autoimmune diseases. For these models, genetically identical, inbred mice have commonly been used. Different inbred mouse strains, however, show a high variability in disease manifestation. Identifying the factors that influence this disease variability could provide unrecognized insights into pathogenesis. We established a novel Ab transfer-induced model of epidermolysis bullosa acquisita (EBA), an autoimmune disease characterized by (muco)-cutaneous blistering caused by anti-type VII collagen (COL7) autoantibodies. Blistering after anti-COL7 IgG (directed against the von Willebrand factor A-like domain 2) transfer showed clear variability among inbred mouse strains, that is, severe cutaneous blistering and inflammation in C57BL/6J and absence of skin lesions in MRL/MpJ mice. The transfer of anti-COL7 IgG into irradiated, EBA-resistant MRL/MpJ mice, rescued by transplantation with bone marrow from EBA-susceptible B6.AK-H2k mice, induced blistering. To the contrary, irradiated EBA-susceptible B6.AK-H2k mice that were rescued using MRL/MpJ bone marrow were devoid of blistering. In vitro, immune complex activation of neutrophils from C57BL/6J or MRL/MpJ mice showed an impaired reactive oxygen species release from the latter, whereas no differences were observed after PMA activation. This finding was paralleled by divergent expression profiles of immune complex-activated neutrophils from either C57BL/6J or MRL/MpJ mice. Collectively, we demonstrate that radiosensitive cells determine the varying extent of skin inflammation and blistering in the end-stage effector phase of EBA.

Application of electron microscopic analysis and fluorescent in situ hybridization technique for the successful diagnosis of extraskeletal Ewing's sarcoma

The diagnosis of soft tissue tumors is often challenging. Immunohistochemical investigation, let alone routine histopathological investigation, may not allow definitive diagnosis in some cases. To overcome such difficulties, more advanced techniques need to be adopted. Herein, we report an extremely rare 56-year-old Japanese female case of extraskeletal Ewing's sarcoma (ES), successfully diagnosed by electron microscopy (EM) using formalin-fixed sections and fluorescence in situ hybridization (FISH). The patient had a 2-year history of a tumor growing on the leg. In routine histopathology, invasive proliferation of tumor cells was observed in the dermis. Tumor cells were round and uniform with large hyperchromatic nuclei, which were positively stained for CD56, VS38c, Ki-67, MIC2 and vimentin, but not for pan-keratin AE1 + AE3, cytokeratin 20, chromogranin A, synaptophysin and neuron-specific enolase. As these findings were not conclusive to make the final diagnosis, EM specimens were prepared from formalin-fixed sections and subjected to investigation. Cell surface projections and dense core granules were detected, suggestive of either Merkel cell carcinoma or extraskeletal ES. Subsequent FISH analysis identified reciprocal translocation of the ESWR1 gene, enabling the final diagnosis of extraskeletal ES. This study provides useful information enabling the diagnosis of this uncommon soft tissue tumor.

Pathological characterization of pachydermia in pachydermoperiostosis

Pachydermoperiostosis is a rare hereditary disease, which presents with the cutaneous manifestations of pachydermia and cutis verticis gyrata. Histological findings in pachydermia frequently include dermal edema, mucin deposition, elastic fiber degeneration, dermal fibrosis and adnexal hyperplasia. However, the severity of these findings varies between clinical reports, and a systematic multiple-case clinicopathological correlative analysis has not been performed to date. In the present study, we reviewed the skin biopsy specimens obtained from the pachydermia of six pachydermoperiostosis patients. The severity of the characteristic histological features was semiquantitatively evaluated and correlated with the grade of pachydermia. Dermal edema, mucin deposition and elastic fiber degeneration were observed in all cases. Patients with severe pachydermia had sebaceous gland hyperplasia and fibrosis. These results suggest that the triad of mucin deposition, dermal edema and elastic fiber degeneration are found from very early stage pachydermia, and could be considered diagnostic findings. To ensure an earlier diagnosis of pachydermoperiostosis, a biopsy should be taken when a patient has grade 1 pachydermia to determine the presence of this histological triad.

Fcγ receptors III and IV mediate tissue destruction in a novel adult mouse model of bullous pemphigoid

Bullous pemphigoid (BP) and epidermolysis bullosa acquisita are subepidermal autoimmune blistering diseases mediated by autoantibodies against type XVII collagen (Col17) and Col7, respectively. For blister formation, Fc-mediated events, such as infiltration of inflammatory cells in the skin, complement activation, and release of proteases at the dermal-epidermal junction, are essential. Although in the neonatal passive transfer mouse model of BP, tissue destruction is mediated by Fcγ receptors (FcγRs) I and III, the passive transfer model of epidermolysis bullosa acquisita completely depends on FcγRIV. To clarify this discrepancy, we developed a novel experimental model for BP using adult mice. Lesion formation was Fc mediated because γ-chain-deficient mice and mice treated with anti-Col17 IgG, depleted from its sugar moiety at the Fc portion, were resistant to disease induction. By the use of various FcγR-deficient mouse strains, tissue destruction was shown to be mediated by FcγRIV, FcγRIII, and FcγRIIB, whereas FcγRI was not essential. Furthermore, anti-inflammatory mediators in already clinically diseased mice can be explored in the novel BP model, because the pharmacological inhibition of FcγRIV and depletion of granulocytes abolished skin blisters. Herein, we extended our knowledge about the importance of FcγRs in experimental BP and established a novel BP mouse model suitable to study disease development over a longer time period and explore novel treatment strategies in a quasi-therapeutic setting.

Mutations in SERPINB7, encoding a member of the serine protease inhibitor superfamily, cause Nagashima-type palmoplantar keratosis

"Nagashima-type" palmoplantar keratosis (NPPK) is an autosomal recessive nonsyndromic diffuse palmoplantar keratosis characterized by well-demarcated diffuse hyperkeratosis with redness, expanding on to the dorsal surfaces of the palms and feet and the Achilles tendon area. Hyperkeratosis in NPPK is mild and nonprogressive, differentiating NPPK clinically from Mal de Meleda. We performed whole-exome and/or Sanger sequencing analyses of 13 unrelated NPPK individuals and identified biallelic putative loss-of-function mutations in SERPINB7, which encodes a cytoplasmic member of the serine protease inhibitor superfamily. We identified a major causative mutation of c.796C>T (p.Arg266(∗)) as a founder mutation in Japanese and Chinese populations. SERPINB7 was specifically present in the cytoplasm of the stratum granulosum and the stratum corneum (SC) of the epidermis. All of the identified mutants are predicted to cause premature termination upstream of the reactive site, which inhibits the proteases, suggesting a complete loss of the protease inhibitory activity of SERPINB7 in NPPK skin. On exposure of NPPK lesional skin to water, we observed a whitish spongy change in the SC, suggesting enhanced water permeation into the SC due to overactivation of proteases and a resultant loss of integrity of the SC structure. These findings provide an important framework for developing pathogenesis-based therapies for NPPK.

Quantification of allergic and irritant patch test reactions using ImageJ

BACKGROUND/AIMS

It is often difficult to differentiate between allergic and irritant patch test reactions by visual inspection. The purpose of this study was to test an image analysis-based method that differentiates between the two reactions by quantifying the degree of erythema at the patch test site.

METHODS

A total of 172 Japanese patients were patch-tested with sodium lauryl sulfate (SLS) and nickel sulfate, followed by digital photography and visual evaluation of the patch test areas by dermatologists at 48 and 72 h. The digital images were converted to erythema index (EI) images by image processing, and changes in ΔEI (the difference in the EI between the patch test site and the adjacent normal skin) values were analyzed.

RESULTS

The ΔEI was significantly increased at 72 h relative to that at 48 h for positive nickel sulfate reactions (P < 0.0001), while no significant difference in the ΔEI was found for SLS reactions.

CONCLUSION

Using image analysis, allergic patch test reactions may be distinguished from irritant reactions by evaluating the change in the degree of erythema at 48 and 72 h.

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.

Identification of mutations in the prostaglandin transporter gene SLCO2A1 and its phenotype-genotype correlation in Japanese patients with pachydermoperiostosis

BACKGROUND

Pachydermoperiostosis (PDP) is a rare genetic disorder characterized by 3 major symptoms: pachydermia including cutis verticis gyrata (CVG), periostosis, and finger clubbing. Recently, a homozygous mutation in the gene HPGD, which encodes 15-hydroxyprostaglandin dehydrogenase (15-PGDH), was found to be associated with PDP. However, mutations in HPGD have not been identified in Japanese PDP patients.

OBJECTIVE

We aimed to identify a novel responsible gene for PDP using whole exome sequencing by next-generation DNA sequencer (NGS).

METHODS

Five patients, including 2 patient-parent trios were enrolled in this study. Entire coding regions were sequenced by NGS to identify candidate mutations associated with PDP. The candidate mutations were subsequently sequenced using the Sanger method. To determine clinical characteristics, we analyzed histological samples, as well as serum and urinary prostaglandin E2 (PGE2) levels for each of the 5 PDP patients, and 1 additional patient with idiopathic CVG.

RESULTS

From initial analyses of whole exome sequencing data, we identified mutations in the solute carrier organic anion transporter family, member 2A1 (SLCO2A1) gene, encoding prostaglandin transporter, in 3 of the PDP patients. Follow-up Sanger sequencing showed 5 different SLCO2A1 mutations (c.940+1G>A, p.E427_P430del, p.G104*, p.T347I, p.Q556H) in 4 unrelated PDP patients. In addition, the splice-site mutation c.940+1G>A identified in 3 of 4 PDP patients was determined to be a founder mutation in the Japanese population. Furthermore, it is likely that the combination of these SLCO2A1 mutations in PDP patients is also associated with disease severity.

CONCLUSION

We found that SLCO2A1 is a novel gene responsible for PDP. Although the SLCO2A1 gene is only the second gene discovered to be associated with PDP, it is likely to be a major cause of PDP in the Japanese population.