Safety and efficacy of intra-erythrocyte dexamethasone sodium phosphate in children with ataxia telangiectasia (ATTeST): a multicentre, randomised, double-blind, placebo-controlled phase 3 trial.

BACKGROUND: Ataxia telangiectasia is a multisystem disorder with progressive neurodegeneration. Corticosteroids can improve neurological functioning in patients with the disorder but adrenal suppression and symptom recurrence on treatment discontinuation has limited their use, prompting the development of novel steroid delivery systems. The aim of the ATTeST study was to evaluate the efficacy and safety of intra-erythrocyte delivery of dexamethasone sodium phosphate compared with placebo in children with ataxia telangiectasia. METHODS: This multicentre, randomised, double-blind, placebo-controlled, phase 3 trial was done at 22 centres in 12 countries (Australia, Belgium, Germany, India, Israel, Italy, Norway, Poland, Spain, Tunisia, the UK, and the USA). Eligible participants were children aged 6 years or older weighing more than 15 kg who met clinical criteria for ataxia telangiectasia but who had preserved autonomous gait. Participants were randomly assigned (1:1:1) to low-dose (approximately 5-10 mg), or high-dose (approximately 14-22 mg) intra-erythrocyte dexamethasone sodium phosphate, or placebo, using an independent interactive web response system, with minimisation for sex and age (6-9 years vs ≥10 years). Intravenous intra-erythrocyte dexamethasone sodium phosphate was administered once a month for 6 months. Participants, employees of the sponsor, investigators, all raters of efficacy endpoints, and central reviewers were masked to treatment assignment and dose allocations. The primary efficacy endpoint was change in the modified International Cooperative Ataxia Rating Scale (mICARS) from baseline to month 6, assessed in the modified intention-to-treat (mITT) population, which included all randomly assigned participants who received at least one dose of study drug and had at least one post-baseline efficacy assessment. This trial is registered with Clinicaltrials.gov (NCT02770807) and is complete. FINDINGS: Between March 2, 2017, and May 13, 2021, 239 children were assessed for eligibility, of whom 176 were randomly assigned. One patient assigned to high-dose intra-erythrocyte dexamethasone sodium phosphate did not initiate treatment. 175 patients received at least one dose of treatment (59 patients received the low dose and 57 received the high dose of intra-erythrocyte dexamethasone sodium phosphate, and 59 received placebo). The mITT population comprised 164 participants (56 children in the low-dose group, 54 children in the high-dose group, and 54 in the placebo group). Compared with the placebo group, no differences were identified with regard to change in mICARS score from baseline to 6 months in the low-dose group (least squares mean difference -1·37 [95% CI -2·932 to 0·190]) or the high-dose group (-1·40 [-2·957 to 0·152]; p=0·0765). Adverse events were reported in 43 (73%) of 59 participants in the low-dose group, 47 (82%) of 57 participants in the high-dose group, and 43 (73%) of 59 participants in the placebo group. Serious adverse events were observed in six (10%) of 59 participants in the low-dose group, seven (12%) of 57 participants in the high-dose group, and seven (12%) of 59 participants in the placebo group. There were no reports of hyperglycaemia, hypertension, hirsutism, or Cushingoid appearance in any of the treatment groups, nor any treatment-related deaths. INTERPRETATION: Although there were no safety concerns, the primary efficacy endpoint was not met, possibly related to delays in treatment reducing the number of participants who received treatment as outlined in the protocol, and potentially different treatment effects according to age. Studies of intra-erythrocyte delivery of dexamethasone sodium phosphate will continue in participants aged 6-9 years, on the basis of findings from subgroup analyses from this trial. FUNDING: EryDel and Quince Therapeutics.

Long term outcome in non-multiple sclerosis paediatric acquired demyelinating syndromes.

OBJECTIVES: We aimed to study the risks of relapse and long term disability in children with non-MS acquired demyelinating syndromes (ADS). METHODS: In this prospective, multi-centre study, from the 14 UK pediatric neurology centres, children (<16 years) experiencing a first episode of ADS were recruited from 2010 to 2014. Case report forms were collected prospectively. RESULTS: A total of 269 children were recruited and followed up for a median of 7.2 years. Median age at onset was 9y (IQR 9.5-14.5, 126 females). At last follow-up, 46 (18 %) had MS, 4 AQP4-Ab NMOSD and 206 (80 %) had other ADS, of which 27 (13 %) relapsed. Relapsing MOGAD was the diagnosis in 12/27, 6 were seronegative and 9 did not have antibodies tested. Frequency of relapse differed according to first presentation in non-MS ADS, being least likely in transverse myelitis (p = 0.025). In the non-MS group, MOG-Ab was predictive of relapse (HR = 8.42; p < 0.001) occurring 8 times as often decreasing over time. Long-term difficulties did not differ between children with monophasic vs relapsing diseases. CONCLUSION: The risk of relapse in non-MS ADS depends on initial diagnosis, and MOG-Ab positivity. Long-term difficulties are observed regardless of relapses and are determined by presenting phenotype.

Feasibility of whole-body MRI for cancer screening in children and young people with ataxia telangiectasia: A mixed methods cross-sectional study.

BACKGROUND/OBJECTIVES: Ataxia telangiectasia (A-T) is an inherited multisystem disorder with increased sensitivity to ionising radiation and elevated cancer risk. Although other cancer predisposition syndromes have established cancer screening protocols, evidence-based guidelines for cancer screening in A-T are lacking. This study sought to assess feasibility of a cancer screening protocol based on whole-body MRI (WB-MRI) in children and young people with A-T. DESIGN/METHODS: Children and young people with A-T were invited to undergo a one-off non-sedated 3-Tesla WB-MRI. Completion rate of WB-MRI was recorded and diagnostic image quality assessed by two experienced radiologists, with pre-specified success thresholds for scan completion of >50% participants and image quality between acceptable to excellent in 65% participants. Positive imaging findings were classified according to the ONCO-RADS system. Post-participation interviews were performed with recruited families to assess the experience of participating and feelings about waiting for, and communication of, the findings of the scan. RESULTS: Forty-six children and young people with A-T were identified, of which 36 were eligible to participate, 18 were recruited and 16 underwent WB-MRI. Nineteen parents participated in interviews. Fifteen participants (83%) completed the full WB-MRI scan protocol. The pre-specified image quality criterion was achieved with diagnostic images obtained in at least 93% of each MRI sequence. Non-malignant scan findings were present in 4 (25%) participants. Six themes were identified from the interviews: (1) anxiety is a familiar feeling, (2) the process of MRI scanning is challenging for some children and families, (3) preparation is essential to reduce stress, (4) WB-MRI provides the reassurance about the physical health that families need, (5) WB-MRI experience turned out to be a positive experience and (6) WB-MRI allows families to be proactive. CONCLUSION: This study shows that WB-MRI for cancer screening is feasible and well-accepted by children and young people with A-T and their families.

Consensus recommendations for the assessment and management of idiopathic intracranial hypertension in children and young people.

BACKGROUND: Idiopathic intracranial hypertension (IIH) is a potentially disabling condition. There is a lack of evidence and national guidance on how to diagnose and treat paediatric IIH, leading to variation in clinical practice. We conducted a national Delphi consensus via the Children's Headache Network to propose a best-practice diagnostic and therapeutic pathway. METHODS: The Delphi process was selected as the most appropriate methodology for examining current opinion among experts in the UK. 104 questions were considered by 66 healthcare professionals, addressing important aspects of IIH care: assessment, diagnosis, treatment, follow-up and surveillance. General paediatricians, paediatric neurologists, ophthalmologists, opticians, neuroradiologists and neurosurgeons with a clinical interest or experience in IIH, were invited to take part. RESULTS: The Delphi process consisted of three rounds comprising 104 questions (round 1, 67; round 2, 24; round 3 (ophthalmological), 13) and was completed between March 2019 and August 2021. There were 54 and 65 responders in the first and second rounds, respectively. The Delphi was endorsed by the Royal College of Ophthalmologists, which engaged 59 ophthalmologists for round 3. CONCLUSIONS: This UK-based Delphi consensus process reached agreement for the management of paediatric IIH and has been endorsed by the Children's Headache Network and more broadly, the British Paediatric Neurology Association. It provides a basis for a pragmatic clinical approach. The recommendations will help to improve clinical care while minimising under and over diagnosis.

Structure-Switching Electrochemical Aptasensor for Rapid, Reagentless, and Single-Step Nanomolar Detection of C-Reactive Protein.

C-reactive protein (CRP) is an acute-phase reactant and sensitive indicator for sepsis and other life-threatening pathologies, including systemic inflammatory response syndrome. Currently, clinical turn-around times for established CRP detection methods take between 30 min to hours or even days from centralized laboratories. Here, we report the development of an electrochemical biosensor using redox probe-tagged DNA aptamers, functionalized onto inexpensive, commercially available screen-printed electrodes. Binding-induced conformational switching of the CRP-targeting aptamer induces a specific and selective signal-ON event, which enables single-step and reagentless detection of CRP in as little as 1 min. The aptasensor limit of detection spans approximately 20-60 nM in 50% human serum with dynamic response windows spanning 1-200 or 1-500 nM (R = 0.97/R = 0.98 respectively). The sensor is stable for at least 1 week and can be reused numerous times, as judged from repeated real-time dosing and dose-response assays. By decoupling binding events from the signal induction mechanism, structure-switching electrochemical aptamer-based sensors provide considerable advantages over their adsorption-based counterparts. Our work expands on the retinue of such sensors reported in the literature and is the first instance of structure-switching electrochemical aptamer-based sensors (SS-EABs) for reagentless, voltammetric CRP detection. We hope this study inspires further investigations into the suitability of SS-EABs for diagnostics, which will aid translational R&D toward fully realized devices aimed at point-of-care applications or for broader use by the public.

Acute pyelonephritis in cats is frequently caused by Escherichia coli resistant to potentiated penicillins but has a better prognosis than other causes of acute kidney injury.

OBJECTIVE: To describe the clinical findings, microbiological data, treatment, and outcome of a population of cats with suspected acute pyelonephritis (APN). ANIMALS: 32 client-owned cats. CLINICAL PRESENTATION AND PROCEDURES: Retrospective case series from 2 veterinary teaching hospitals between January 1, 2014, and December 31, 2020. Cats were included if they had a positive bacterial urine culture and a clinical diagnosis of acute kidney injury. RESULTS: Older female cats with underlying chronic kidney disease have a higher probability to develop bacterial culture-positive acute kidney injury or APN. Escherichia coli was the most commonly cultured bacterial species, and E coli isolates with susceptibility testing were resistant to amoxicillin-clavulanate but susceptible to fluoroquinolones or third-generation cephalosporins. Of the 20 cats with available follow-up information in the medical record, 14 were alive at 3 months after hospital discharge. Markers of renal function including creatinine (P = .008), BUN (P = .005), and phosphorus (P < .001) at the time of presentation were all higher in nonsurvivors compared with survivors. CLINICAL RELEVANCE: The survival rate with feline APN is higher than previous reports of acute kidney injury when all etiologies are considered. Nonsurvivors had more pronounced azotemia upon initial presentation. Amoxicillin-clavulanate was a poor empirical antimicrobial in this cohort based on the microbiological data.

The Care and Management of Children and Young People with Ataxia Telangiectasia Provided by Nurses and Allied Health Professionals: a Scoping Review.

Ataxia telangiectasia (A-T) is a rare, multisystem progressive condition that typically presents in early childhood. In the absence of cure, people with A-T require coordinated multidisciplinary care to manage their complex array of needs and to minimize the disease burden. Although symptom management has proven benefits for this population, including improved quality of life and reduced complications, there is a need for guidance specific to the nursing and allied healthcare teams who provide care within the community. A scoping review, adopting the Joanna Briggs Institute methodology, was undertaken. It aimed to identify and map the available expertise from nursing and allied healthcare and management of children and young people with A-T ≤ 18 years of age. A rigorous search strategy was employed which generated a total of 21,118 sources of evidence, of which 50 were selected for review following screening by experts. A range of interventions were identified that reported a positive impact on A-T-related impairments, together with quality of life, indicating that outcomes can be improved for this population. Most notable interventions specific to A-T include therapeutic exercise, inspiratory muscle training, and early nutritional assessment and intervention. Further research will be required to determine the full potential of the identified interventions, including translatability to the A-T setting for evidence related to other forms of ataxia. Large gaps exist in the nursing and allied health evidence-base, highlighting a need for robust research that includes children and young people with A-T and their families to better inform and optimize management strategies.

Development of cancer surveillance guidelines in ataxia telangiectasia: A Delphi-based consensus survey of international experts.

BACKGROUND/OBJECTIVES: Ataxia telangiectasia (A-T) is a multiorgan disorder with increased vulnerability to cancer. Despite this increased cancer risk, there are no widely accepted guidelines for cancer surveillance in people affected by A-T. We aimed to understand the current international practice regarding cancer surveillance in A-T and agreed-upon approaches to develop cancer surveillance in A-T. DESIGN/METHODS: We used a consensus development method, the e-Delphi technique, comprising three rounds. Round 1 consisted of a Delphi questionnaire and a survey that collected the details of respondents' professional background, experience, and current practice of cancer surveillance in A-T. Rounds 2 and 3 were designed based on previous rounds and modified according to the comments made by the panellists. The pre-specified consensus threshold was ≥75% agreement. RESULTS: Thirty-five expert panellists from 13 countries completed the study. The survey indicated that the current practice of cancer surveillance varies widely between experts and centres'. Consensus was reached that evidence-based guidelines are needed for cancer surveillance in people with A-T, with separate recommendations for adults and children. Statements relating to the tests that should be included, the age for starting and stopping cancer surveillance and the optimal surveillance interval were also agreed upon, although in some areas, the consensus was that further research is needed. CONCLUSION: The international expert consensus statement confirms the need for evidence-based cancer surveillance guidelines in A-T, highlights key features that the guidelines should include, and identifies areas of uncertainty in the expert community. This elucidates current knowledge gaps and will inform the design of future clinical trials.

Whole-body MRI for cancer surveillance in ataxia-telangiectasia: A qualitative study of the perspectives of people affected by A-T and their families.

BACKGROUND/OBJECTIVES: Ataxia-telangiectasia (A-T) is a complex inherited disease associated with an increased risk of malignancy. Surveillance guidelines have demonstrated significant health benefits in other cancer predisposition syndromes. However, evidence-based guidelines for cancer screening are not currently used in the United Kingdom for people affected by A-T. This study aims to understand how people with A-T and their parents feel about cancer surveillance using whole-body magnetic resonance imaging (MRI) to inform the future development of cancer surveillance guidelines. DESIGN/METHODS: We conducted semistructured interviews with people affected by A-T. Data were analysed inductively using thematic analysis. RESULTS: Nine parents of children with A-T and four adults with A-T were interviewed. Five main themes emerged from the data, including (1) cancer screening was considered invaluable with the perceived value of early detection highlighted; (2) the cancer fear can increase anxiety; (3) the perceived limitations around current practice, with the responsibility for monitoring falling too strongly on parents and patients; (4) the need for effective preparation for cancer screening, including clear communication and (5) the challenges associated with MRI screening, where specific recommendations were made for improving the child's experience. CONCLUSION: This study suggests that stakeholders are positive about the perceived advantages of a cancer screening programme. Ongoing support and preparation techniques should be adopted to maximise adherence and minimise adverse psychosocial outcomes. PATIENT OR PUBLIC CONTRIBUTION: People with A-T and parents of people with A-T were actively involved in this study by giving their consent to be interviewed. An independent parent representative contributed to the study, supporting the research team in interpreting and commenting on the appropriateness of the language used in this report.

A clinically utilized intravenous continuous rate infusion of diltiazem does not significantly decrease systolic function in healthy dogs.

OBJECTIVE: To determine if left ventricular systolic function on echocardiography, systemic blood pressure, and electrocardiography change with a clinically accepted intravenous (IV) diltiazem constant rate infusion (CRI) compared to a control. ANIMALS: 10 healthy client-owned adult dogs. PROCEDURES: Prospective, masked, crossover study from May 27, 2021, to August 22, 2021. Dogs were randomized to receive diltiazem (loading dose of 240 µg/kg, IV followed by a CRI of 6 µg/kg/min for 300 minutes) or the same volume of 5% dextrose in water (D5W) administered IV followed by the opposite intervention after a 7-day washout. Blood pressure was monitored during each CRI, and echocardiographic and electrocardiographic studies were performed immediately before the CRI and during the last hour of the CRI. RESULTS: Postdiltiazem systolic time interval (STI) (median, 0.30; range, 0.16 to 0.34) was significantly lower than post-D5W STI (median, 0.32; range, 0.22 to 0.40; P = .046). All other echocardiographic parameters did not differ significantly between each of the groups after receiving diltiazem or D5W. Systemic blood pressure did not change significantly with either diltiazem (P = .450) or D5W (P = .940), and none of the dogs became hypotensive at any point in the study. Expectedly, negative dromotropy was observed with diltiazem. CLINICAL RELEVANCE: A significant decrease in left ventricular systolic function was not appreciated in healthy dogs receiving diltiazem at a clinically accepted intravenous infusion rate at this dosing regimen. Further studies are needed in dogs with cardiac disease.

Effects of an intravenous infusion of diltiazem on glomerular filtration rate, electrolyte excretion, and urine output in healthy dogs.

BACKGROUND: Acute kidney injury (AKI) in dogs has a high case fatality rate. Diltiazem might improve renal function, but effect of intravenous infusion has not been adequately studied in dogs. HYPOTHESIS/OBJECTIVES: To determine if an intravenous infusion of diltiazem improves renal function through changes in glomerular filtration rate (GFR), fractional excretion of sodium (FENa), and urine output (UOP) in healthy dogs. ANIMALS: Ten healthy adult dogs. METHODS: Prospective, unmasked, crossover study. Dogs were randomized to receive diltiazem (loading dose of 240 µg/kg followed by 6 µg/kg/min for 300 min) or the same volume of 5% dextrose in water (D5W). The opposite treatment was given after a 7-day washout period. GFR and FENa were obtained at baseline and after infusion. UOP was measured starting 1 hour before diltiazem administration. RESULTS: GFR did not significantly increase from baseline with diltiazem (before diltiazem median = 2.371 mL/min/kg, range = 1.605-4.359; after diltiazem median = 2.305 mL/min/kg, range = 1.629-4.387; median difference = 0.080 mL/min/kg, 95% confidence interval [CI] = -0.417 to 0.757; P = .85), and there was no difference in D5W GFR before and after diltiazem (median = 2.389 mL/min/kg, range = 1.600-3.557; median difference = 0.036 mL/min/kg, 95% CI = -0.241 to 1.112; P = .69). FENa did not increase from baseline after administration of diltiazem (median difference = 0%, 95% CI = -0.1 to 0.1; P = .81), and there was no difference in D5W FENa (median difference = 0.1%, 95% CI = -0.1 to 0.2; P = .26). UOP did not increase with diltiazem (P = .06). CONCLUSION AND CLINICAL IMPORTANCE: Intravenous administration of diltiazem does not improve markers of renal function in healthy dogs. Further studies are needed in dogs with AKI.

Neonatal stroke surveillance study protocol in the United Kingdom and Republic of Ireland.

Neonatal stroke is a devastating condition that causes brain injury in babies and often leads to lifelong neurological impairment. Recent prospective population studies of neonatal stroke are lacking. Neonatal strokes are different from those in older children and adults. A better understanding of its aetiology, current management, and outcomes could reduce the burden of this rare condition. The study aims to explore the incidence and 2 year outcomes of neonatal stroke across an entire population in the UK and Republic of Ireland. This is an active national surveillance study using a purpose-built integrated case notification-data collection online platform. Over a 13 month period, with a potential 6 month extension, clinicians will notify neonatal stroke cases presenting in the first 90 days of life electronically via the online platform monthly. Clinicians will complete a primary questionnaire via the platform detailing clinical information, including neuroimaging, for analysis and classification. An outcome questionnaire will be sent at 2 years of age via the platform. Appropriate ethics and regulatory approvals have been received. The neonatal stroke study represents the first multinational population surveillance study delivered via a purpose-built integrated case notification-data collection online platform and data safe haven, overcoming the challenges of setting up the study.

Quality of life and neurological disability in children and young people with ataxia telangiectasia.

AIM: To explore neurological factors affecting quality of life (QoL) in children and young people with ataxia-telangiectasia (A-T), from both child and parent perspective. METHOD: 24 children/young people with A-T (mean age 11.2 ± 3.5 years; 13 males) and 20 parents were recruited, and 58% were reassessed after an average interval of 3.4 years. Participants completed the PedsQL QoL assessment. Participants with A-T underwent structured neurological examination. QoL data from 20 healthy controls and their parents was used for comparison. RESULTS: Children/young people with A-T rated their QoL higher than parental ratings across time points, with no longitudinal change. Higher age of the child participant correlated with lower parental (r = -0.43, p = .008) but not child ratings of QoL (r = -0.16, p = .380). Child and parent QoL ratings from the A-T group were lower than respective ratings from controls (ηp2 = 0.44 and ηp2 = 0.75 respectively, both p < .0005, controlled for socioeconomic status). Parental, but not child, ratings of QoL was predicted by a regression model based on neurological scores (R2 = 0.44, p=<.001). INTERPRETATION: Neurological disability does not determine child/young person QoL ratings in A-T. While certain aspects of neurological disability predict parent-proxy ratings, there is no decline in QoL over time. These results may reflect resilience in the face of a complex life-limiting disorder.

The natural history of ataxia-telangiectasia (A-T): A systematic review.

BACKGROUND: Ataxia-telangiectasia is an autosomal recessive, multi-system, and life-shortening disease caused by mutations in the ataxia-telangiectasia mutated gene. Although widely reported, there are no studies that give a comprehensive picture of this intriguing condition. OBJECTIVES: Understand the natural history of ataxia-telangiectasia (A-T), as reported in scientific literature. SEARCH METHODS: 107 search terms were identified and divided into 17 searches. Each search was performed in PubMed, Ovid SP (MEDLINE) 1946-present, OVID EMBASE 1980 -present, Web of Science core collection, Elsevier Scopus, and Cochrane Library. SELECTION CRITERIA: All human studies that report any aspect of A-T. DATA COLLECTION AND ANALYSIS: Search results were de-duplicated, data extracted (including author, publication year, country of origin, study design, population, participant characteristics, and clinical features). Quality of case-control and cohort studies was assessed by the Newcastle-Ottawa tool. Findings are reported descriptively and where possible data collated to report median (interquartile range, range) of outcomes of interest. MAIN RESULTS: 1314 cases reported 2134 presenting symptoms. The most common presenting symptom was abnormal gait (1160 cases; 188 studies) followed by recurrent infections in classical ataxia-telangiectasia and movement disorders in variant ataxia-telangiectasia. 687 cases reported 752 causes of death among which malignancy was the most frequently reported cause. Median (IQR, range) age of death (n = 294) was 14 years 0 months (10 years 0 months to 23 years 3 months, 1 year 3 months to 76 years 0 months). CONCLUSIONS: This review demonstrates the multi-system involvement in A-T, confirms that neurological symptoms are the most frequent presenting features in classical A-T but variants have diverse manifestations. We found that most individuals with A-T have life limited to teenage or early adulthood. Predominance of case reports, and case series demonstrate the lack of robust evidence to determine the natural history of A-T. We recommend population-based studies to fill this evidence gap.

What is new in migraine management in children and young people?

For this narrative review, we found recent publications on the use and effectiveness of old therapies including nutraceuticals, such as riboflavin, vitamin D, magnesium, melatonin and talking therapies. Recent large trials of established conventional pharmaceuticals such as propranolol, pizotifen, topiramate and amitriptyline for childhood migraine have failed, but the use of a quasi-placebo in future trials could help. We reviewed the evidence for angiotensin antagonists including candesartan in adults, but found a lack of evidence for their use in children. There have been new developments in pharmaceuticals recently, including a more selective 5-HT1F agonist, lasmiditan, an effective acute treatment with no vasoconstrictor activity in adults, currently being tested in children. Also, a number of new calcitonin gene-related peptide (CGRP) antibodies and antagonists, with proven efficacy in acute treatment and/or prevention of migraine in adults, are undergoing trials in children. Peripheral nerve blocks and botulinum toxin are gaining popularity in adult practice, but we really need more good quality evidence for their effectiveness in children. Finally, electroceuticals, that is, therapeutic electric devices, are now marketed for acute and or preventative treatment, including an external trigeminal nerve stimulator (e-TNS), a non-invasive vagal nerve stimulator (nVNS), a single-pulse transcranial magnetic stimulator (sTMS) and a remote electrical neuromodulation device (REN). At the moment, evidence for their effectiveness in children is still lacking. So, there has been much progress, but mostly for adults. We are in urgent need of more migraine trials in children.

Feline sarcomatoid renal cell carcinoma with peritoneal carcinomatosis and effusion.

A 9-y-old, castrated male, domestic medium-hair cat diagnosed previously with chronic kidney disease developed anorexia and vomiting. Ultrasonography revealed abdominal effusion and a left renal perihilar mass. Cytologic evaluation of the peritoneal fluid and mass identified atypical epithelioid cells suspected to be of renal epithelial or possible mesothelial origin. Immunohistochemical (IHC) evaluation of a formalin-fixed, paraffin-embedded peritoneal fluid cell block indicated both pancytokeratin and vimentin expression in the atypical epithelioid cell population. With scanning electron microscopic evaluation, similar epithelioid cells lacked the cell-surface microvilli expected of mesothelium, supporting an antemortem diagnosis of probable carcinoma. On postmortem examination, the left kidney was effaced by an infiltrative neoplasm with myriad similar nodules throughout the peritoneum. The neoplasm was composed primarily of polygonal-to-spindle-shaped cells with strong vimentin and weak pancytokeratin cytoplasmic immunolabeling. Further IHC characterization with PAX8, CK18, KIT, napsin A, SMA, desmin, CD18, and claudin 5 was performed. Histologic and IHC findings supported a diagnosis of sarcomatoid renal cell carcinoma with peritoneal carcinomatosis. An in vitro cell culture line of neoplastic cells harvested from the primary tumor was successfully established for future research endeavors.