A prenatal skin atlas reveals immune regulation of human skin morphogenesis.

Human prenatal skin is populated by innate immune cells, including macrophages, but whether they act solely in immunity or have additional functions in morphogenesis is unclear. Here we assembled a comprehensive multi-omics reference atlas of prenatal human skin (7-17 post-conception weeks), combining single-cell and spatial transcriptomics data, to characterize the microanatomical tissue niches of the skin. This atlas revealed that crosstalk between non-immune and immune cells underpins the formation of hair follicles, is implicated in scarless wound healing and is crucial for skin angiogenesis. We systematically compared a hair-bearing skin organoid (SkO) model derived from human embryonic stem cells and induced pluripotent stem cells to prenatal and adult skin1. The SkO model closely recapitulated in vivo skin epidermal and dermal cell types during hair follicle development and expression of genes implicated in the pathogenesis of genetic hair and skin disorders. However, the SkO model lacked immune cells and had markedly reduced endothelial cell heterogeneity and quantity. Our in vivo prenatal skin cell atlas indicated that macrophages and macrophage-derived growth factors have a role in driving endothelial development. Indeed, vascular network remodelling was enhanced following transfer of autologous macrophages derived from induced pluripotent stem cells into SkO cultures. Innate immune cells are therefore key players in skin morphogenesis beyond their conventional role in immunity, a function they achieve through crosstalk with non-immune cells.

A roadmap for the Human Developmental Cell Atlas.

The Human Developmental Cell Atlas (HDCA) initiative, which is part of the Human Cell Atlas, aims to create a comprehensive reference map of cells during development. This will be critical to understanding normal organogenesis, the effect of mutations, environmental factors and infectious agents on human development, congenital and childhood disorders, and the cellular basis of ageing, cancer and regenerative medicine. Here we outline the HDCA initiative and the challenges of mapping and modelling human development using state-of-the-art technologies to create a reference atlas across gestation. Similar to the Human Genome Project, the HDCA will integrate the output from a growing community of scientists who are mapping human development into a unified atlas. We describe the early milestones that have been achieved and the use of human stem-cell-derived cultures, organoids and animal models to inform the HDCA, especially for prenatal tissues that are hard to acquire. Finally, we provide a roadmap towards a complete atlas of human development.

Blood and immune development in human fetal bone marrow and Down syndrome.

Haematopoiesis in the bone marrow (BM) maintains blood and immune cell production throughout postnatal life. Haematopoiesis first emerges in human BM at 11-12 weeks after conception1,2, yet almost nothing is known about how fetal BM (FBM) evolves to meet the highly specialized needs of the fetus and newborn. Here we detail the development of FBM, including stroma, using multi-omic assessment of mRNA and multiplexed protein epitope expression. We find that the full blood and immune cell repertoire is established in FBM in a short time window of 6-7 weeks early in the second trimester. FBM promotes rapid and extensive diversification of myeloid cells, with granulocytes, eosinophils and dendritic cell subsets emerging for the first time. The substantial expansion of B lymphocytes in FBM contrasts with fetal liver at the same gestational age. Haematopoietic progenitors from fetal liver, FBM and cord blood exhibit transcriptional and functional differences that contribute to tissue-specific identity and cellular diversification. Endothelial cell types form distinct vascular structures that we show are regionally compartmentalized within FBM. Finally, we reveal selective disruption of B lymphocyte, erythroid and myeloid development owing to a cell-intrinsic differentiation bias as well as extrinsic regulation through an altered microenvironment in Down syndrome (trisomy 21).

Midfacial toddler excoriation syndrome (MiTES): case series, diagnostic criteria and evidence for a pathogenic mechanism.

BACKGROUND: PRDM12 polyalanine tract expansions cause two different disorders: midfacial toddler excoriation syndrome (MiTES; itch with normal pain sensation associated with 18 homozygous alanines (18A); and congenital insensitivity to pain (CIP) with normal itch associated with 19 homozygous alanines (19A). Knowledge of the phenotype, genotype and disease mechanism of MiTES is incomplete. Why 18A vs. 19A PRDM12 can cause almost opposite phenotypes is unknown; no other polyalanine or polyglutamine tract expansion disease causes two such disparate phenotypes. OBJECTIVES: To assess the genotype and phenotype of nine new, nine atypical and six previously reported patients diagnosed with MiTES. METHODS: Using cell lines with homozygous PR domain zinc finger protein 12 (PRDM12) containing 12 alanines (12A; normal), 18A (MiTES) and 19A (CIP), we examined PRDM12 aggregation and subcellular localization by image-separation confocal microscopy and subcellular fractionation Western blotting. RESULTS: MiTES presents in the first year of life; in all cases the condition regresses over the first decade, leaving scarring. The MiTES phenotype is highly distinctive. Features overlapping with PRDM12 CIP are rarely found. The genotype-phenotype study of the PRDM12 polyalanine tract shows that having 7-15 alanines is normal; 16-18 alanines is associated with MiTES; 19 alanines leads to CIP; and no clinically atypical cases of MiTES had a polyalanine tract expansion. PRDM12 aggregation and subcellular localization differed significantly between 18A and normal 12A cell lines and between 18A and 19A cell lines. MiTES is a new protein-aggregation disease. CONCLUSIONS: We provide diagnostic criteria for MiTES and improved longitudinal data. MiTES and CIP are distinct phenotypes, despite their genotypes varying by a single alanine in the PRDM12 polyalanine tract. We found clear distinctions between the cellular phenotypes of normal, MiTES and CIP cells. We hypothesize that the developmental environment of the trigeminal ganglion is unique and critically sensitive to pre- and postnatal levels of PRDM12.

Midfacial toddler excoriation syndrome (MiTES) causes facial itching and scratching in babies during their first year of life. MiTES tends to improve over the time period of approximately 10 years, but it can leave scars. Congenital insensitivity to pain (CIP) is a condition where a person cannot feel pain and is present from birth. This study looked at two conditions: MiTES and CIP. We specifically investigated changes in a gene called PRDM12, focusing on a part of the gene called the polyalanine tract ­ a sequence of many alanines (alanine is a type of amino acid). We discovered that the normal range for this sequence is between 7 and 15 alanines. If there are 16 to 18 alanines, it is associated with MiTES and causes the PRDM12 protein to clump together inside the cell. However, if there are 19 alanines, it leads to CIP, and the PRDM12 protein clumps together and moves to the cytoplasm, where it should not be. We found new evidence to suggest that MiTES is a disease where proteins clump together. Overall, our study findings show that despite there only being a small change in the same gene, MiTES and CIP are very different conditions.

Determining the clinical applicability of machine learning models through assessment of reporting across skin phototypes and rarer skin cancer types: A systematic review.

Machine learning (ML) models for skin cancer recognition may have variable performance across different skin phototypes and skin cancer types. Overall performance metrics alone are insufficient to detect poor subgroup performance. We aimed (1) to assess whether studies of ML models reported results separately for different skin phototypes and rarer skin cancers, and (2) to graphically represent the skin cancer training datasets used by current ML models. In this systematic review, we searched PubMed, Embase and CENTRAL. We included all studies in medical journals assessing an ML technique for skin cancer diagnosis that used clinical or dermoscopic images from 1 January 2012 to 22 September 2021. No language restrictions were applied. We considered rarer skin cancers to be skin cancers other than pigmented melanoma, basal cell carcinoma and squamous cell carcinoma. We identified 114 studies for inclusion. Rarer skin cancers were included by 8/114 studies (7.0%), and results for a rarer skin cancer were reported separately in 1/114 studies (0.9%). Performance was reported across all skin phototypes in 1/114 studies (0.9%), but performance was uncertain in skin phototypes I and VI from minimal representation of the skin phototypes in the test dataset (9/3756 and 1/3756, respectively). For training datasets, although public datasets were most frequently used, with the most widely used being the International Skin Imaging Collaboration (ISIC) archive (65/114 studies, 57.0%), the largest datasets were private. Our review identified that most ML models did not report performance separately for rarer skin cancers and different skin phototypes. A degree of variability in ML model performance across subgroups is expected, but the current lack of transparency is not justifiable and risks models being used inappropriately in populations in whom accuracy is low.

Systemic interventions for treatment of Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS/TEN overlap syndrome.

BACKGROUND: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS/TEN overlap syndrome are rare, severe cutaneous adverse reactions usually triggered by medications. In addition to tertiary-level supportive care, various systemic therapies have been used including glucocorticoids, intravenous immunoglobulins (IVIGs), cyclosporin, N-acetylcysteine, thalidomide, infliximab, etanercept, and plasmapheresis. There is an unmet need to understand the efficacy of these interventions. OBJECTIVES: To assess the effects of systemic therapies (medicines delivered orally, intramuscularly, or intravenously) for the treatment of SJS, TEN, and SJS/TEN overlap syndrome. SEARCH METHODS: We searched the following databases up to March 2021: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, and Embase. We also searched five clinical trial registers, the reference lists of all included studies and of key review articles, and a number of drug manufacturer websites. We searched for errata or retractions of included studies. SELECTION CRITERIA: We included only randomised controlled trials (RCTs) and prospective observational comparative studies of participants of any age with a clinical diagnosis of SJS, TEN, or SJS/TEN overlap syndrome. We included all systemic therapies studied to date and permitted comparisons between each therapy, as well as between therapy and placebo. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures as specified by Cochrane. Our primary outcomes were SJS/TEN-specific mortality and adverse effects leading to discontinuation of SJS/TEN therapy. Secondary outcomes included time to complete re-epithelialisation, intensive care unit length of stay, total hospital length of stay, illness sequelae, and other adverse effects attributed to systemic therapy. We rated the certainty of the evidence for each outcome using GRADE. MAIN RESULTS: We included nine studies with a total of 308 participants (131 males and 155 females) from seven countries. We included two studies in the quantitative meta-analysis. We included three RCTs and six prospective, controlled observational studies. Sample sizes ranged from 10 to 91. Most studies did not report study duration or time to follow-up. Two studies reported a mean SCORe of Toxic Epidermal Necrosis (SCORTEN) of 3 and 1.9. Seven studies did not report SCORTEN, although four of these studies reported average or ranges of body surface area (BSA) (means ranging from 44% to 51%). Two studies were set in burns units, two in dermatology wards, one in an intensive care unit, one in a paediatric ward, and three in unspecified inpatient units. Seven studies reported a mean age, which ranged from 29 to 56 years. Two studies included paediatric participants (23 children). We assessed the results from one of three RCTs as low risk of bias in all domains, one as high, and one as some concerns. We judged the results from all six prospective observational comparative studies to be at a high risk of bias. We downgraded the certainty of the evidence because of serious risk of bias concerns and for imprecision due to small numbers of participants. The interventions assessed included systemic corticosteroids, tumour necrosis factor-alpha (TNF-alpha) inhibitors, cyclosporin, thalidomide, N-acetylcysteine, IVIG, and supportive care. No data were available for the main comparisons of interest as specified in the review protocol: etanercept versus cyclosporin, etanercept versus IVIG, IVIG versus supportive care, IVIG versus cyclosporin, and cyclosporin versus corticosteroids. Corticosteroids versus no corticosteroids It is uncertain if there is any difference between corticosteroids (methylprednisolone 4 mg/kg/day for two more days after fever had subsided and no new lesions had developed) and no corticosteroids on disease-specific mortality (risk ratio (RR) 2.55, 95% confidence interval (CI) 0.72 to 9.03; 2 studies; 56 participants; very low-certainty evidence). Time to complete re-epithelialisation, length of hospital stay, and adverse effects leading to discontinuation of therapy were not reported. IVIG versus no IVIG It is uncertain if there is any difference between IVIG (0.2 to 0.5 g/kg cumulative dose over three days) and no IVIG in risk of disease-specific mortality (RR 0.33, 95% CI 0.04 to 2.91); time to complete re-epithelialisation (mean difference (MD) -2.93 days, 95% CI -4.4 to -1.46); or length of hospital stay (MD -2.00 days, 95% CI -5.81 to 1.81). All results in this comparison were based on one study with 36 participants, and very low-certainty evidence. Adverse effects leading to discontinuation of therapy were not reported. Etanercept (TNF-alpha inhibitor) versus corticosteroids Etanercept (25 mg (50 mg if weight > 65 kg) twice weekly "until skin lesions healed") may reduce disease-specific mortality compared to corticosteroids (intravenous prednisolone 1 to 1.5 mg/kg/day "until skin lesions healed") (RR 0.51, 95% CI 0.16 to 1.63; 1 study; 91 participants; low-certainty evidence); however, the CIs were consistent with possible benefit and possible harm. Serious adverse events, such as sepsis and respiratory failure, were reported in 5 of 48 participants with etanercept and 9 of 43 participants with corticosteroids, but it was not clear if they led to discontinuation of therapy. Time to complete re-epithelialisation and length of hospital stay were not reported. Cyclosporin versus IVIG  It is uncertain if there is any difference between cyclosporin (3 mg/kg/day or intravenous 1 mg/kg/day until complete re-epithelialisation, then tapered off (10 mg/day reduction every 48 hours)) and IVIG (continuous infusion 0.75 g/kg/day for 4 days (total dose 3 g/kg) in participants with normal renal function) in risk of disease-specific mortality (RR 0.13, 95% CI 0.02 to 0.98, 1 study; 22 participants; very low-certainty evidence). Time to complete re-epithelialisation, length of hospital stay, and adverse effects leading to discontinuation of therapy were not reported. No studies measured intensive care unit length of stay. AUTHORS' CONCLUSIONS: When compared to corticosteroids, etanercept may result in mortality reduction. For the following comparisons, the certainty of the evidence for disease-specific mortality is very low: corticosteroids versus no corticosteroids,  IVIG versus no IVIG and cyclosporin versus IVIG. There is a need for more multicentric studies, focused on the most important clinical comparisons, to provide reliable answers about the best treatments for SJS/TEN.

Vaccines for COVID-19: learning from ten phase II trials to inform clinical and public health vaccination programmes.

Public health professionals and clinicians, in many countries, are immersed in the ongoing and upcoming vaccination programmes for COVID-19. Published information from vaccine trials is complex. There are important and helpful insights about the nature of the available and forthcoming vaccines, immune responses and side-effects from phase II trials. We have systematically summarised information from 10 such trials on the nature of the vaccines, exclusions from the trials, immunological effects and side-effects. Some important information within these trial reports is not available in the phase III trial articles, so a complete picture requires examination of phase II and phase III trials for each vaccine. We recommend our systematic approach for the examination of other upcoming COVID-19 vaccine phase II and III trials.

Reliable Detection of Eczema Areas for Fully Automated Assessment of Eczema Severity from Digital Camera Images.

Assessing the severity of eczema in clinical research requires face-to-face skin examination by trained staff. Such approaches are resource-intensive for participants and staff, challenging during pandemics, and prone to inter- and intra-observer variation. Computer vision algorithms have been proposed to automate the assessment of eczema severity using digital camera images. However, they often require human intervention to detect eczema lesions and cannot automatically assess eczema severity from real-world images in an end-to-end pipeline. We developed a model to detect eczema lesions from images using data augmentation and pixel-level segmentation of eczema lesions on 1,345 images provided by dermatologists. We evaluated the quality of the obtained segmentation compared with that of the clinicians, the robustness to varying imaging conditions encountered in real-life images, such as lighting, focus, and blur, and the performance of downstream severity prediction when using the detected eczema lesions. The quality and robustness of eczema lesion detection increased by approximately 25% and 40%, respectively, compared with that of our previous eczema detection model. The performance of the downstream severity prediction remained unchanged. Use of skin segmentation as an alternative to eczema segmentation that requires specialist labeling showed the performance on par with when eczema segmentation is used.

Yolk sac cell atlas reveals multiorgan functions during human early development.

The extraembryonic yolk sac (YS) ensures delivery of nutritional support and oxygen to the developing embryo but remains ill-defined in humans. We therefore assembled a comprehensive multiomic reference of the human YS from 3 to 8 postconception weeks by integrating single-cell protein and gene expression data. Beyond its recognized role as a site of hematopoiesis, we highlight roles in metabolism, coagulation, vascular development, and hematopoietic regulation. We reconstructed the emergence and decline of YS hematopoietic stem and progenitor cells from hemogenic endothelium and revealed a YS-specific accelerated route to macrophage production that seeds developing organs. The multiorgan functions of the YS are superseded as intraembryonic organs develop, effecting a multifaceted relay of vital functions as pregnancy proceeds.

Structural brain changes in First Episode Schizophrenia compared with Fronto-Temporal Lobar Degeneration: a meta-analysis.

BACKGROUND: The authors sought to compare gray matter changes in First Episode Schizophrenia (FES) compared with Fronto-Temporal Lobar Degeneration (FTLD) using meta-analytic methods applied to neuro-imaging studies. METHODS: A systematic search was conducted for published, structural voxel-based morphometric MRI studies in patients with FES or FTLD. Data were combined using anatomical likelihood estimation (ALE) to determine the extent of gray matter decreases and analysed to ascertain the degree of overlap in the spatial distribution of brain changes in both diseases. RESULTS: Data were extracted from 18 FES studies (including a total of 555 patients and 621 comparison subjects) and 20 studies of FTLD or related disorders (including a total of 311 patients and 431 comparison subjects). The similarity in spatial overlap of brain changes in the two disorders was significant (p = 0.001). Gray matter deficits common to both disorders included bilateral caudate, left insula and bilateral uncus regions. CONCLUSIONS: There is a significant overlap in the distribution of structural brain changes in First Episode Schizophrenia and Fronto-Temporal Lobar Degeneration. This may reflect overlapping aetiologies, or a common vulnerability of these regions to the distinct aetio-pathological processes in the two disorders.

Detecting Eczema Areas in Digital Images: An Impossible Task?

Assessing the severity of atopic dermatitis (AD, or eczema) traditionally relies on a face-to-face assessment by healthcare professionals and may suffer from inter- and intra-rater variability. With the expanding role of telemedicine, several machine learning algorithms have been proposed to automatically assess AD severity from digital images. Those algorithms usually detect and then delineate (segment) AD lesions before assessing lesional severity and are trained using the data of AD areas detected by healthcare professionals. To evaluate the reliability of such data, we estimated the inter-rater reliability of AD segmentation in digital images. Four dermatologists independently segmented AD lesions in 80 digital images collected in a published clinical trial. We estimated the inter-rater reliability of the AD segmentation using the intraclass correlation coefficient at the pixel and the area levels for different resolutions of the images. The average intraclass correlation coefficient was 0.45 ( standard error = 0.04 ) corresponding to a poor agreement between raters, whereas the degree of agreement for AD segmentation varied from image to image. The AD segmentation in digital images is highly rater dependent even among dermatologists. Such limitations need to be taken into consideration when AD segmentation data are used to train machine learning algorithms that assess eczema severity.

Evidence-based management of eczema: five things that should be done more and five things that should be dropped.

PURPOSE OF REVIEW: We provide readers with an evidence-informed opinion on current treatments for eczema (atopic dermatitis) with the intention of improving patient care. We suggest five treatment aspects that should be promoted and five that should be demoted. Evidence sources include key randomized controlled trials and systematic reviews. RECENT FINDINGS: Under-treatment of eczema can be countered by more aggressive use of topical therapies including the 'get control then keep control' regimen, and systemics for severe disease, supplemented with good patient education. Topical corticosteroids should be used once daily rather than twice daily. Topical calcineurin inhibitors are useful for sensitive sites. There is little evidence to support the continued use of oral antihistamines, oral or topical antistaphylococcal treatments for infected eczema or probiotics for treating eczema. Nonpharmacological treatments including silk clothing, ion-exchange water softeners and emollient bath additives have not been shown to benefit eczema patients. Despite promising pilot studies, large trials suggest that emollients from birth do not prevent eczema and may result in harms such as increased skin infections and food allergy. SUMMARY: New evidence-based insights on existing and newer treatments allow clinicians the opportunity to change their practice in a way that enhances patients' quality of life.

Defining the Skin Cellular Community Using Single-Cell Genomics to Advance Precision Medicine.

Single-cell genomics has revolutionized biological science, enabling high-resolution analysis of human tissues. The ability to demonstrate the role and function of distinct cell types comprising human tissues paves the way for a new understanding of cellular pathways, interactions, and future research directions. The skin, easily accessible and possessing a diverse and complex role in defending us both physically and immunologically from the outside world, lends itself ideally to single-cell genomics analysis. Here, we outline the benefits of single-cell RNA sequencing while also highlighting the challenges in achieving a meaningful result from its use. Key milestones relating to the study of skin in this way are introduced, covering both healthy and diseased states, and we discuss the potential promise of single-cell RNA sequencing to result in tangible medical advances, with a particular focus on precision medicine.

Population perspective comparing COVID-19 to all and common causes of death during the first wave of the pandemic in seven European countries.

OBJECTIVES: Mortality statistics on the COVID-19 pandemic have led to widespread concern and fear. To contextualise these data, we compared mortality related to COVID-19 during the first wave of the pandemic across seven countries in Europe with all and common causes of death, stratifying by age and sex. We also calculated deaths as a proportion of the population by age and sex. STUDY DESIGN: Analysis of population mortality data. METHODS: COVID-19 related mortality and population statistics from seven European countries were extracted: England and Wales, Italy, Germany, Spain, France, Portugal and Netherlands. Available data spanned 14-16 weeks since the first recorded deaths in each country, except Spain, where only comparable stratified data over an 8-week time period was available. The Global Burden of Disease database provided data on all deaths and those from pneumonia, cardiovascular disease combining ischaemic heart disease and stroke, chronic obstructive pulmonary disease, cancer, road traffic accidents and dementia in 2017. RESULTS: Deaths related to COVID-19, while modest overall, varied considerably by age. Deaths as a percentage of all cause deaths during the time period under study ranged from <0.01% in children in Germany, Portugal and Netherlands, to as high as 41.65% for men aged over 80 years in England and Wales. The percentage of the population who died from COVID-19 was less than 0.2% in every age group under the age of 80. In each country, over the age of 80, these proportions were: England and Wales 1.27% males, 0.87% females; Italy 0.6% males, 0.38% females; Germany 0.13% males, 0.09% females; France 0.39% males, 0.2% females; Portugal 0.2% males, 0.15% females; and Netherlands 0.6% males, 0.4% females. CONCLUSIONS: Mortality rates from COVID-19 during the first wave of the pandemic were low including when compared to other common causes of death and are likely to decline further while control measures are maintained, treatments improve and vaccination is instituted. These data may help people to contextualise their risk and for decision-making by policymakers.

Single-cell multi-omics analysis of the immune response in COVID-19.

Analysis of human blood immune cells provides insights into the coordinated response to viral infections such as severe acute respiratory syndrome coronavirus 2, which causes coronavirus disease 2019 (COVID-19). We performed single-cell transcriptome, surface proteome and T and B lymphocyte antigen receptor analyses of over 780,000 peripheral blood mononuclear cells from a cross-sectional cohort of 130 patients with varying severities of COVID-19. We identified expansion of nonclassical monocytes expressing complement transcripts (CD16+C1QA/B/C+) that sequester platelets and were predicted to replenish the alveolar macrophage pool in COVID-19. Early, uncommitted CD34+ hematopoietic stem/progenitor cells were primed toward megakaryopoiesis, accompanied by expanded megakaryocyte-committed progenitors and increased platelet activation. Clonally expanded CD8+ T cells and an increased ratio of CD8+ effector T cells to effector memory T cells characterized severe disease, while circulating follicular helper T cells accompanied mild disease. We observed a relative loss of IgA2 in symptomatic disease despite an overall expansion of plasmablasts and plasma cells. Our study highlights the coordinated immune response that contributes to COVID-19 pathogenesis and reveals discrete cellular components that can be targeted for therapy.

Developmental cell programs are co-opted in inflammatory skin disease.

The skin confers biophysical and immunological protection through a complex cellular network established early in embryonic development. We profiled the transcriptomes of more than 500,000 single cells from developing human fetal skin, healthy adult skin, and adult skin with atopic dermatitis and psoriasis. We leveraged these datasets to compare cell states across development, homeostasis, and disease. Our analysis revealed an enrichment of innate immune cells in skin during the first trimester and clonal expansion of disease-associated lymphocytes in atopic dermatitis and psoriasis. We uncovered and validated in situ a reemergence of prenatal vascular endothelial cell and macrophage cellular programs in atopic dermatitis and psoriasis lesional skin. These data illustrate the dynamism of cutaneous immunity and provide opportunities for targeting pathological developmental programs in inflammatory skin diseases.

Thyrotoxicosis Associated with Ustekinumab Treatment for Psoriasis.

Biologic treatments have revolutionised the management of psoriasis in recent years; however, data on their safety profile in large populations and long-term effects are being gathered on an ongoing basis. Ustekinumab is a monoclonal antibody that targets interleukin-12/23 used in the treatment of moderate-to-severe psoriasis. Here, we report the case of a 32-year-old Caucasian gentleman who developed thyrotoxicosis following the commencement of ustekinumab treatment. Following control of thyroid status by the Endocrinology team, this recurred after recommencement of ustekinumab on two further occasions over a 5-year period. This is the second known reported association of this nature. Awareness of these possible adverse effects is imperative in managing patients and informing decision-making, and further long-term studies will help elucidate the precise safety profiles of biologic treatments.

Medical leadership in the NHS during the COVID-19 pandemic.

Amid the global COVID-19 pandemic, adaptation of healthcare systems, with strong medical leadership, has been integral to coping with the ever-changing situation. This article is based on the personal experiences of doctors in the NHS and insights into the frontline response to this situation. It reflects on leadership dilemmas and strategies implemented to overcome them, with a focus on systems thinking and adaptive leadership.

Cutaneous Polyarteritis Nodosa Presenting Atypically with Severe Pharyngeal Ulceration.

Polyarteritis nodosa (PAN) is a multisystem, necrotising vasculitis of small- and medium-sized arteries with a predilection for the visceral vessels. Cutaneous PAN is a rare variant with symptomatic vasculitis limited to the skin, typically presenting as nodular lesions on the extremities with a propensity to ulcerate. We describe a rare case of histologically confirmed cutaneous PAN presenting in a 55-year-old Ghanaian woman with severe oropharyngeal ulceration. This was associated with dysphagia and significant weight loss. Oesophagoduodenoscopy showed that the ulceration extended throughout the oropharynx. Systemic polyarteritis nodosa was ruled out with magnetic resonance angiography. Our patient was treated successfully with corticosteroids and methotrexate. This case suggests that cutaneous PAN should be considered in the differential diagnosis of patients with oropharyngeal ulceration and that histological assessment is pivotal in establishing the diagnosis early in order to instigate appropriate therapy.