Dissecting hair breakage in alopecia areata: the central role of dysregulated cysteine homeostasis.

In the initial stages of Alopecia Areata (AA), the predominance of hair breakage or exclamation mark hairs serves as vital indicators of disease activity. These signs are non-invasive and are commonly employed in dermatoscopic examinations. Despite their clinical salience, the underlying etiology precipitating this hair breakage remains largely uncharted territory. Our exhaustive review of the existing literature points to a pivotal role for cysteine-a key amino acid central to hair growth-in these mechanisms. This review will probe and deliberate upon the implications of aberrant cysteine metabolism in the pathogenesis of AA. It will examine the potential intersections of cysteine metabolism with autophagy, ferroptosis, immunity, and psychiatric manifestations associated with AA. Such exploration could illuminate new facets of the disease's pathophysiology, potentially paving the way for innovative therapeutic strategies.

Role of neurogenic inflammation in the pathogenesis of alopecia areata.

Alopecia areata refers to an autoimmune illness indicated by persistent inflammation. The key requirement for alopecia areata occurrence is the disruption of immune-privileged regions within the hair follicles. Recent research has indicated that neuropeptides play a role in the damage to hair follicles by triggering neurogenic inflammation, stimulating mast cells ambient the follicles, and promoting apoptotic processes in keratinocytes. However, the exact pathogenesis of alopecia areata requires further investigation. Recently, there has been an increasing focus on understanding the mechanisms of immune diseases resulting from the interplay between the nervous and the immune system. Neurogenic inflammation due to neuroimmune disorders of the skin system may disrupt the inflammatory microenvironment of the hair follicle, which plays a crucial part in the progression of alopecia areata.

Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences.

Both alopecia areata (AA) and vitiligo are distinct, heterogenous, and complex disease entities, characterized by nonscarring scalp terminal hair loss and skin pigment loss, respectively. In AA, inflammatory cell infiltrates are in the deep reticular dermis close to the hair bulb (swarm of bees), whereas in vitiligo the inflammatory infiltrates are in the epidermis and papillary dermis. Immune privilege collapse has been extensively investigated in AA pathogenesis, including the suppression of immunomodulatory factors (e.g., transforming growth factor-ß (TGF-ß), programmed death-ligand 1 (PDL1), interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and macrophage migration inhibitory factor (MIF)) and enhanced expression of the major histocompatibility complex (MHC) throughout hair follicles. However, immune privilege collapse in vitiligo remains less explored. Both AA and vitiligo are autoimmune diseases that share commonalities in pathogenesis, including the involvement of plasmacytoid dendritic cells (and interferon-α (IFN- α) signaling pathways) and cytotoxic CD8+ T lymphocytes (and activated IFN-γ signaling pathways). Blood chemokine C-X-C motif ligand 9 (CXCL9) and CXCL10 are elevated in both diseases. Common factors that contribute to AA and vitiligo include oxidative stress, autophagy, type 2 cytokines, and the Wnt/ß-catenin pathway (e.g., dickkopf 1 (DKK1)). Here, we summarize the commonalities and differences between AA and vitiligo, focusing on their pathogenesis.

Refractory alopecia areata with single hairs imitating frontal fibrosing alopecia: a prospective observational study.

BACKGROUND: Lonely hair sign is considered as a clue to the diagnosis of frontal fibrosing alopecia (FFA). OBJECTIVE: To report an undescribed variant of alopecia areata (AA) with which the patient developed single hairs and other features similar to FFA and to determine the underlying mechanism. METHODS: We conducted a prospective observational study in patients who presented with receding hairline and single hairs, evaluating the clinical, trichoscopic, and histological features and their correlation. Immunochemistry studies were performed to describe the microenvironment. RESULTS: Eighteen patients were enrolled in the study. Despite the similarity to FFA clinically, these patients showed different histopathology which revealed a normal number of pilosebaceous units, one anagen hair in one or more pilosebaceous units, and others in telogen stage, consistent with single hairs under the naked eye or under trichoscopy. The severity of the hair loss assessed by SALT was no more than 50, but the response to conventional therapy was poor. CONCLUSIONS: This study reports a unique variant of AA. The pathological basis is an increase in the telogen hair follicles, with one anagen hair in one or more pilosebaceous units. Minimal inflammation consisting of CD3+ T lymphocytes and mast cells was demonstrated in the microenvironment.

[Alopecia and COVID-19: possible etiopathogenetic variants and therapeutic approach]. / Alopetsiya i COVID-19: vozmozhnye etiopatogeneticheskie varianty i printsipy lecheniya.

Sudden hair thinning, phantom trichalgia in the early and late rehabilitation period after novel coronavirus infection (COVID-19) are the most common complaints of patients, that can be considered by both dermatocosmetologist and medical rehabilitation specialist. A telogen hair loss was found in 19.8% of patients, whereby 27.3% of patients suffering from hair loss during disease and 72.7% - at 3rd-6th month after recovery. Most commonly, hair loss is non-structural and associated with an abnormal ovulatory cycle shift and diffuse asynchronous loss of hair follicles in telogen phase, as well as with an increase of total predisposed to loss hair follicles number. Nevertheless, the analysis of clinical observations of patients with post-COVID hair loss has shown that this disorder is registered not only in telogen phase. There is a rapid disease progression up to the final stages in the presence of verified androgenetic alopecia diagnosis. The cases of alopecia areata and cicatricial alopecia, associated with previous COVID-19, also were registered. Androgenetic alopecia is the first (30.7%) and diffuse alopecia is the second (19.8%) by degree of incidence. The relapses or much less frequently the onsets of alopecia areata and the unexplained pronounced pain at the hair roots in parietal region (7.8%) are in the third place. The article presents in detail the possible reasons and mechanisms of hair loss associated with COVID-19, determines necessary examinations with consideration to the scientific analysis of domestic and foreign literature sources.

Linear alopecia in pediatrics: RCM and dermoscopy reveal diagnostic cues.

BACKGROUND: Alopecia areata (AA), trichotillomania (TM), nevus sebaceous (NS), and linear scleroderma en coup de sabre (LSCS) can all present with a patch of linear alopecia, making diagnosis challenging. The purpose of this study was to combine reflectance confocal microscopy (RCM) and dermoscopy in the diagnosis of these lesions in children. METHODS: A total of 36 patients with linear alopecia were enrolled, of whom 14 had AA, seven had TM, nine had NS, and six had LSCS. We evaluated the characteristics and distinguishing features of the four conditions using RCM and dermoscopy. RESULTS: The key to differential diagnosis was the dermal Hair follicle density in the dermis was decreased in AA, and the size and density of the follicular openings were normal in TM. In NS, the major features were petal-like and frogspawn-like structures. In LSCS, dermal papillary rings, sebaceous glands, and follicles were partially or completely missing, and abundant fibrous material was distributed in the dermis. Dermoscopy revealed alopecia, and all four conditions resulted in decreased hair density. AA patients exhibited yellow dots, black dots, and exclamation mark hairs. TM patients presented with irregularly broken hairs and blood spots. Both NS and LSCS patients exhibited an absence of follicular openings; NS patients demonstrated whitish and yellowish round structures, while an atrophic area with white patches, linear vessels, and no yellow or black dots was observed in LSCS patients CONCLUSION: RCM combined with dermoscopy can provide additional information on disease states and differentiate between AA, TM, NS, and LSCS.

Alopecia areata: What's new in the epidemiology, comorbidities, and pathogenesis?

BACKGROUND: Alopecia areata (AA) is a common, acquired, and nonscarring type of hair loss that affects people of every generation and is intractable in severe and relapsing cases. Patients with AA, especially those with greater scalp involvement, have poor health-related quality-of-life scores. PURPOSE: Following our previous review article in the April 2017 issue of the Journal of Dermatological Science, we aim to provide a pair of review articles on recent progress in multidisciplinary approaches to AA. MAIN FINDINGS: We found more than 1800 publications on AA from July 2016 to December 2022. CONCLUSIONS: In this review, we focused on the latest information on the epidemiology, comorbidities, and pathogenesis of AA.

Clinical characteristics and immune profiles of patients with immune-mediated alopecia associated with COVID-19 vaccinations.

BACKGROUND: The clinical characteristics and pathomechanism for immune-mediated alopecia following COVID-19 vaccinations are not clearly characterized. OBJECTIVE: We investigated the causality and immune mechanism of COVID-19 vaccines-related alopecia areata (AA). STUDY DESIGN: 27 new-onset of AA patients after COVID-19 vaccinations and 106 vaccines-tolerant individuals were enrolled from multiple medical centers for analysis. RESULTS: The antinuclear antibody, total IgE, granulysin, and PARC/CCL18 as well as peripheral eosinophil count were significantly elevated in the patients with COVID-19 vaccines-related AA compared with those in the tolerant individuals (P = 2.03 × 10-5-0.039). In vitro lymphocyte activation test revealed that granulysin, granzyme B, and IFN-γ released from the T cells of COVID-19 vaccines-related AA patients could be significantly increased by COVID-19 vaccine excipients (polyethylene glycol 2000 and polysorbate 80) or spike protein (P = 0.002-0.04). CONCLUSIONS: Spike protein and excipients of COVID-19 vaccines could trigger T cell-mediated cytotoxicity, which contributes to the pathogenesis of immune-mediated alopecia associated with COVID-19 vaccines.

Follicular dysplasia and hair loss in white-tailed deer (Odocoileus virginianus).

There have been unpublished reports of a follicular dysplastic syndrome in adult white-tailed deer (Odocoileus virginianus; WTD), known colloquially as "toothpaste hair disease." The current report aims to describe the gross and histologic lesions in skin samples from 2 adult WTDs that presented to the Wisconsin Department of Natural Resources and the Wisconsin Veterinary Diagnostic Laboratory with reports of hair loss in 2018. Both cases were grossly alopecic with sparing of the distal extremities and variably the head and neck. Histologic features included hair follicles and adnexa present in relatively normal numbers, dilated and misshapen follicles, and dysplastic hair bulbs. Hair follicles were empty, contained fragmented and irregular hair shafts, or contained concretions of keratin. Hair bulbs were rarely infiltrated by small lymphocytes, suggestive of alopecia areata as a cause of the gross appearance. This condition does not appear to be directly responsible for WTD mortality but presumably would predispose affected animals to greater environmental exposure. Evaluation of additional affected individuals is warranted to further evaluate for features of alopecia areata.

Diagnosis and differential diagnosis of tertiary androgenetic alopecia with severe alopecia areata based on high-resolution MRI.

BACKGROUND AND AIM: No previous study investigated the anatomical changes of the scalp and hair follicles between tertiary androgenetic alopecia and severe alopecia areata using high-resolution magnetic resonance imaging (HR-MRI). This study aimed to explore the value of HR-MRI in assessing alopecia. MATERIALS AND METHODS: Forty-eight people were included in this study. The imaging indicators of the vertex and occipital scalp were recorded and compared. The logistic regression model was developed for the indicators that differed between tertiary androgenetic alopecia and severe alopecia areata. The receiver-operating characteristic (ROC) curve was used to assess the diagnostic efficacy of the model for tertiary androgenetic alopecia and severe alopecia areata. RESULTS: At the vertex, the thickness of the subcutaneous tissue layer, follicle depth, relative follicle depth, total number of follicles within a 2-cm distance, and number of strands reaching the middle and upper third of the subcutaneous fat layer within a 2-cm distance were statistically different between patients with tertiary androgenetic alopecia, those with severe alopecia areata, and healthy volunteers (p < 0.05). The logistic regression model suggested that the subcutaneous tissue layer thickness was important in discriminating tertiary androgenetic alopecia from severe alopecia areata. The ROC curve showed that the area under the curve, sensitivity, specificity, and best cutoff values of the subcutaneous tissue layer were 0.886, 94.4%, 70%, and 4.31 mm, respectively. CONCLUSIONS: HR-MRI can observe the changes in anatomical structures of the scalp and hair follicles in patients with alopecia. HR-MRI can be applied to the differential diagnosis of tertiary androgenetic alopecia and severe alopecia areata.

Sarcoidosis Coexisting With Distinct Forms of Alopecia on the Scalp: A Case Series.

ABSTRACT: Sarcoidosis is an idiopathic multisystem inflammatory disease that can affect virtually any part of the body. Often, it can initially present solely in the skin. Histologically, it is characterized by noncaseating, 'naked' granulomas in the dermis and subcutaneous tissue. Clinically, sarcoidosis is often referred to as a 'mimicker' of many other pathologic processes because of its wide array of presentations. Occasionally, sarcoidosis can present in the scalp as both a scarring and nonscarring alopecia. There are countless reports of sarcoidosis mimicking various other alopecias including acne keloidalis nuchae, discoid lupus erythematosus, frontal fibrosing alopecia, lichen planopilaris, and alopecia areata totalis. In this case series, we present 2 novel cases of sarcoidosis not just clinically mimicking other forms of alopecia but occurring in conjunction with a separate and histologically distinct primary alopecia.

Sintilimab-induced Alopecia Universalis in a Patient With the Anti-tumor Effect of Complete Remission After Hepatectomy.

Immune checkpoint blockades have been widely used to treat various malignancies. Programmed cell death protein 1 (PD-1) inhibitor-induced alopecia areata, one of the immune-related adverse events, is rarely reported. We present a case of alopecia universalis during the treatment of Sintilimab, a monoclonal anti-PD-1 antibody, in a patient with hepatocellular carcinoma. A 65-year-old male was diagnosed with hepatocellular carcinoma in liver segment VI (S6) and chose to receive Sintilimab due to predicted insufficient residual liver volume for hepatectomy. He presented extensive hair loss in all the parts of the body 4 weeks after Sintilimab treatment. And without using any dermatologic drug, the alopecia areata gradually developed to be alopecia universalis after Sintilimab continuous treatment for 21 months. The pathological examination of skin revealed remarkable increased lymphocytes infiltration around the hair follicles, which contained predominantly CD8 positive T cells in the dermis. During single immunotherapy, the tumor marker of serum alpha-fetoprotein level soon decreased from 512.1 mg/L to a normal level within 3 months, accompanied with a remarkable tumor regression in liver S6 by magnetic resonance imaging scans. The patient received hepatectomy and pathological examination demonstrated the nodule was full of extensive necrosis. By combining immunotherapy and hepatectomy, the patient finally achieved a remarkable anti-tumor effect of complete remission. Immune checkpoint blockades-induced alopecia areata is a rare immune-related adverse event and accompanied with a good anti-tumor efficacy in our case. Regardless of alopecia treatment, PD-1 inhibitor treatment is recommended to be continued, especially when the immunotherapy is effective.

Baricitinib as the first systemic treatment for severe alopecia areata.

INTRODUCTION: Alopecia areata is a heterogenous, immune-mediated hair loss disorder that can affect any hair-bearing site on the body. Despite being one of the most prevalent autoimmune skin diseases, treatments have historically been limited to off-label medications that have demonstrated limited efficacy, especially in more severe forms of disease. Thus, there has long been an unmet need for rigorously studied therapeutics in alopecia areata. AREAS COVERED: Janus kinase inhibitors have proven to be an effective class of drugs for treating several inflammatory disorders. One such drug, baricitinib, has recently demonstrated significant hair regrowth in phase 2 and 3 alopecia areata trials. It has since become the first systemic therapy approved for treating severe alopecia areata. This review examines the role of Janus kinase pathways in alopecia areata's pathogenesis and the safety and efficacy of baricitinib for treating severe alopecia areata. EXPERT OPINION: The approval of baricitinib for treating severe alopecia areata marks a major milestone in the disease's history. While baricitinib has proven to be efficacious for this indication and has demonstrated an overall good safety profile, patients' individual risk factors for serious adverse events should be assessed during shared decision-making with patients before initiating treatment.

Biomarkers in alopecia Areata: A systematic review and meta-analysis.

BACKGROUND: Alopecia areata (AA) is an autoimmune non-scarring alopecia that affects the scalp or any hair-bearing areas in the body. The pathophysiology of AA is complex, but Th1, Th2, and Th17 cytokines dysregulation, as well as chemokines, immunoglobulins and other biomarkers have been shown to play a role in the pathogenesis of the disease. OBJECTIVE: To conduct a systematic review and Meta-analysis to identify biomarkers that reflect AA activity and severity that could be used to better assess disease activity and response in both trials and clinical practice. METHODS: A literature search was conducted using the PUBMED, EMBASE and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) from inception to December 2021. Articles reporting on associations between AA and serum clinical biomarkers (cytokines, chemokines, antibodies, immunoglobulins, and others) were included. Serum biomarkers were identified in patients with AA and were correlated with disease severity and patient characteristics (ex. age, sex, comorbidities). The quality of the studies was assessed using the National Heart, Lung, and Blood Institute's Quality Assessment Tool for Case-Control Studies. Meta-analysis pooling of the standardized mean differences (SMD) by the method of Cohen using the common-effect inverse-variance model was performed. For the Meta-analysis, data was pulled for all the markers with a minimum of 4 studies with means and standard deviations. Analysis of data reported as Median with range or inter-quartile range (IQR) revealed that the data was too skewed to recommend calculation and use of mean with standard deviation (SD). If the data were not skewed, mean and SD were calculated. RESULTS: One thousand seven hundred fourteen studies were screened, with 91 included, reporting on a total of 52 biomarkers. Meta-analyses revealed pooled SMD that were significant for interleukin 6 (IL6), C-reactive protein (CRP) and vitamin D. CONCLUSIONS: Serum IL6 and CRP levels are significantly increased in patients with AA compared to healthy age and sex matched controls. Conversely, serum vitamn D levels are significantly decreased in patients with AA compared to healthy age and sex matched controls. This data has the potential to influence the clinical guidelines for the diagnostic workup of AA to include testing the serum levels of CRP and vitamin D.

Involvement of ILC1-like innate lymphocytes in human autoimmunity, lessons from alopecia areata.

Here, we have explored the involvement of innate lymphoid cells-type 1 (ILC1) in the pathogenesis of alopecia areata (AA), because we found them to be significantly increased around lesional and non-lesional HFs of AA patients. To further explore these unexpected findings, we first co-cultured autologous circulating ILC1-like cells (ILC1lc) with healthy, but stressed, organ-cultured human scalp hair follicles (HFs). ILClc induced all hallmarks of AA ex vivo: they significantly promoted premature, apoptosis-driven HF regression (catagen), HF cytotoxicity/dystrophy, and most important for AA pathogenesis, the collapse of the HFs physiological immune privilege. NKG2D-blocking or IFNγ-neutralizing antibodies antagonized this. In vivo, intradermal injection of autologous activated, NKG2D+/IFNγ-secreting ILC1lc into healthy human scalp skin xenotransplanted onto SCID/beige mice sufficed to rapidly induce characteristic AA lesions. This provides the first evidence that ILC1lc, which are positive for the ILC1 phenotype and negative for the classical NK markers, suffice to induce AA in previously healthy human HFs ex vivo and in vivo, and further questions the conventional wisdom that AA is always an autoantigen-dependent, CD8 +T cell-driven autoimmune disease.

Janus Kinase Inhibitors in the Treatment of Alopecia Areata.

Alopecia areata is a disease of autoimmune origin which causes non scarring hair loss. The extent of alopecia varies from a small patch to complete scalp and body hair loss, which can have huge psychosocial impact for those affected. Treatment modalities which have been used so far included nonspecific immunosuppressive medications, such as corticosteroids, cyclosporine, and methotrexate, or topical immunomodulators, such as diphencyprone, dithranol, and squaric acid dibutylester. The recognition of the importance of Janus kinase pathway in alopecia areata pathogenesis enabled more specific approaches in treatment. Positive outcomes of Janus kinase inhibitors in several trials granted approval for baricitinib which became the first on-label treatment for alopecia areata. The aim of this review is to summarize the role, efficacy and safety of several Janus kinase inhibitors in alopecia areata.

A comparative study of histopathologic features in alopecia areata and pattern hair loss.

BACKGROUND: When peribulbar infiltrates are absent, other histopathologic findings are necessary to distinguish alopecia areata (AA) from pattern hair loss (PHL). The purpose of this study is to determine which histopathologic features are most useful for differentiation. METHODS: A retrospective slide review was conducted of AA and PHL scalp biopsy specimens from 2014 to 2019 at a tertiary referral center. RESULTS: Ninety-six cases were retrieved, of which 38 were AA. Peribulbar infiltrates were identified in 24 AA (63.2%) cases. A catagen/telogen shift was observed more frequently in AA than PHL (25 cases, 65.5% vs. 10 cases, 17.2%; p ≤ 0.0001). Lymphocytes (4 cases, 10.5% vs. 1 case, 1.7%; p = 0.058) and melanin (25 cases, 65.8% vs. 5 cases, 8.6%; p ≤ 0.0001) in fibrous tracts were more common in AA. Apoptotic bodies within vellus hairs were more frequently identified in AA (32 cases, 84.2% vs. 37 cases, 63.8%; p = 0.030). Small dystrophic follicles were also more common in AA (16 cases, 42.1% vs. 1 case, 1.7%; p < 0.0001). CONCLUSIONS: Common features of AA other than peribulbar infiltrates include a catagen/telogen shift, melanin in fibrous tracts, and small dystrophic follicles. Practitioners should consider these features when distinguishing AA from PHL in specimens without peribulbar infiltrates. The retrospective design limits our ability to exclude multifactorial alopecia, such as telogen effluvium.

Comparative study between topical steroid alone versus combined fractional Erbium:YAG laser with topical steroid in treatment of alopecia areata.

AA is a common autoimmune skin disease that causes hair loss on the scalp and sometimes other areas of the body. New therapy approaches for alopecia areata are emerging, with the goal of improving clinical outcomes. In this study, the effects of topical steroids against fractional Er:YAG laser followed by topical steroids in the treatment of alopecia areata will be compared. A total of 30 participants with alopecia areata were included in the study. Each patient's lesions were treated with one of two methods: topical clobetasol propionate or fractional Er:YAG laser followed by topical clobetasol propionate. SALT score, patient satisfaction, and dermoscopic imaging were used to evaluate therapeutic response. Both treatment modalities showed a significant clinical improvement in alopecia areata with a statistically significant reduction in the SALT score. The SALT score was more evident in the laser-steroid group. On comparing the dermoscopy findings in both treated areas before and after treatment, a significant reduction was found regarding all dermoscopic findings of alopecia areata in both modalities. Combining fractional Er:YAG laser with topical steroids is found to be a safe treatment modality and more effective than topical steroids in alopecia areata.

Impaired autophagy promotes hair loss in the C3H/HeJ mouse model of alopecia areata.

Alopecia areata (AA) involves an aberrant immune attack on the hair follicle (HF), which leads to hair loss. Previous genetic data from our lab pointed to a connection between macroautophagy/autophagy and AA pathogenesis, and GWAS identified STX17, CLEC16A and BCL2L11/BIM as risk factors for AA. Additionally, AA patients have copy number deletions in region spanning the ATG4B gene. To test whether autophagy might contribute to disease pathogenesis in AA, we investigated autophagic activity in C3H/HeJ mouse model. We found that autophagy protein SQSTM1 accumulated in HF of AA mice, while in immune cells from AA skin-draining lymph nodes SQSTM1 was not altered, suggesting that autophagic activity is inhibited in the HF of AA mice. Induction of autophagy with Tat-BECN1 peptide attenuated AA, while treatment with the autophagy blocker chloroquine promoted disease, compared to untreated AA mice. Together, our findings suggest the involvement of impaired autophagy in disease pathogenesis of AA.Abbreviations: AA: alopecia areata; CQ: chloroquine; GWAS: genome-wide association studies; HF: hair follicle; MHC: major histocompatibility complex; SDLN: skin-draining lymph nodes.

Stratification of alopecia areata reveals involvement of CD4 T cell populations and altered faecal microbiota.

Alopecia areata (AA) is an immune-mediated disease that causes non-scarring hair loss. Autoreactive CD8 T cells are key pathogenic effectors in the skin, and AA has been associated both with atopy and with perturbations in intestinal homeostasis. This study aimed to investigate mechanisms driving AA by characterizing the circulating immunophenotype and faecal microbiome, and by stratifying AA to understand how identified signatures associated with heterogeneous clinical features of the condition. Flow cytometric analyses identified alterations in circulating B cells and CD4 T cells, while 16S sequencing identified changes in alpha and beta diversity in the faecal microbiome in AA. The proportions of transitional and naïve B cells were found to be elevated in AA, particularly in AA samples from individuals with >50% hair loss and those with comorbid atopy, which is commonly associated with extensive hair loss. Although significant changes in circulating CD8 T cells were not observed, we found significant changes in CD4+ populations. In individuals with <50% hair loss higher frequencies of CCR6+CD4 ("Th17") and CCR6+CXCR3+CD4 ("Th1/17") T cells were found. While microbial species richness was not altered, AA was associated with reduced evenness and Shannon diversity of the intestinal microbiota, again particularly in those with <50% hair loss. We have identified novel immunological and microbial signatures in individuals with alopecia areata. Surprisingly, these are associated with lower levels of hair loss, and may therefore provide a rationale for improved targeting of molecular therapeutics.