Citations

Abstract Background The expanding use of biologic and small-molecule therapies for ulcerative colitis (UC) has raised concerns regarding perioperative safety. We conducted a network meta-analysis to compare short-term postoperative complications associated with preoperative exposure to these agents in patients undergoing colorectal surgery. Methods We systematically searched PubMed, Web of Science, and the Cochrane Library through September 15, 2025, for cohort studies of adults with UC who were exposed to biologic or small-molecule therapy within 12 weeks prior to surgery. Interventions included biologic therapy, small-molecule therapy, and no biologic or small-molecule therapy (control). The primary outcome was overall postoperative complications at 30 and 90 days. Venous thromboembolism (VTE) was assessed as a key secondary outcome. Random-effects network meta-analysis was performed using risk ratios (RRs) with 95% confidence intervals (CIs). Results Sixteen retrospective cohort studies involving 3235 patients were included. At 30 days, ustekinumab and tofacitinib were associated with lower overall postoperative complication rates than control (RR: 0.29; 95% CI: 0.09-0.96; and RR: 0.66; 95% CI: 0.46-0.96, respectively). Anti-tumor necrosis factor (TNF) therapy was associated with higher complication rates compared with vedolizumab, ustekinumab, and tofacitinib at 30 days (RR: 1.27; 95% CI: 1.00-1.63; RR: 3.67; 95% CI: 1.12-12.03; and RR: 1.61; 95% CI: 1.14-2.27, respectively). At 90 days, anti-TNF therapy was associated with higher complication rates than control (RR 1.20, 95% CI 1.03-1.40), although the 90-day analysis was based on limited data. VTE rates were similar across treatments at both time points. Conclusion Preoperative ustekinumab and tofacitinib were associated with fewer 30-day postoperative complications than control or anti-TNF therapy, while vedolizumab was associated with fewer complications than anti-TNF therapy. At 90 days, anti-TNF therapy was associated with higher complication rates compared with control. These findings, particularly at 90 days based on limited data, should be interpreted with caution and require confirmation in well-designed prospective studies with rigorous adjustment for confounding factors.

Background: Hypoplastic left heart syndrome (HLHS) is defined as “a spectrum of congenital cardiovascular malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch”. Without treatment, HLHS is usually lethal in the neonate. Many hypotheses have been advanced to explain the etiology of HLHS; however, no single theory appears to fully explain the phenotypic variability seen in HLHS. Furthermore, many of these theories offer no explanations regarding the precipitating events which lead to the development of HLHS. Objective: This review considers and critically evaluates the strengths and weaknesses of the leading theories proposed to explain the pathogenesis of HLHS—including hemodynamic disturbances, primary myocardial structural defects, valvar malformations, and genetic or epigenetic alterations that may provoke developmental and anatomic abnormalities. After presenting each model, we propose a novel, comprehensive, and data-driven framework which may assist researchers in developing models for the pathogenesis of the various subtypes of HLHS. Methods: Key findings from human fetal imaging, histopathology, genetic studies, and animal models were considered, as well as the hypothetical contribution of each in observed HLHS phenotypes. The rationales for these findings as causal factors initiating individual HLHS patterns, as well as how they might contribute to HLHS in general, were critically analyzed. Results: The flow theory is strongly supported by animal models and in utero interventions that demonstrate the impact of altered hemodynamics on cardiac morphogenesis. However, the flow theory fails to identify initial causes of disturbed flow or related histological features of HLHS like endocardial fibroelastosis. The myocardial and valve-first models suggest an important role in developmental defects, but do not necessarily have a strong experimental basis that provides explanations for how they mediate HLHS. Genetic studies in patients with HLHS have identified several candidate causal mutations. However, such genetic causes of HLHS exhibit incomplete phenotypic penetrance and clinical impact. A multifactorial framework attempts to integrate these diverse mechanisms and may provide the most coherent explanation that can accommodate the heterogeneity and variable presentation of HLHS. Such a framework may identify multiple forces that drive disease but does not provide useful pathways for future research about HLHS. Conclusions: No single hypothesis has fully explained how HLHS is initiated, progresses, and presents with the clinical conditions that are encountered by cardiac surgeons and cardiologists. The most current models suggest that the spectrum of HLHS reflects acomplex interaction between genetic susceptibility, flow-dependent cardiac remodeling, and environmental factors in utero. A multifactorial model integrates these diverse mechanisms and may provide the most coherent explanation for the various phenotypic variations in HLHS. Based on our analysis of the most current data and the strengths and weaknesses of the current theoretical frameworks, we propose a novel research strategy aimed at identifying specific cardiac progenitor cell populations whose dysregulation may represent a unifying explanation for the etiology of the various phenotypes of HLHS. Based on the arguments made throughout this manuscript that evaluate the various genetic, structural, and hemodynamic models of initiation of disease, we believe that the significant phenotypic variability across the spectrum of HLHS (i.e., the different anatomic subtypes for “classic” HLHS) most likely reflects different underlying etiologies and mechanisms. At the very least, it is very likely that the timing of the insult is critical in determining anatomic subtype. Based on the published data and the arguments within this manuscript, it seems naive to think that there is a single unifying mechanism explain all forms of HLHLS.

Background: Transanal total mesorectal excision (taTME) facilitates sphincter preservation in low rectal cancer. Preliminary results and functional outcomes from the North American multicenter phase II taTME trial (NCT03144765) have been published. Three-year outcomes are reported. Methods: Patients with stage I to III rectal adenocarcinoma were enrolled across 11 centers (2017–2022). Endpoints included TME grade, 3-year overall survival, disease-free survival, cancer-specific survival, recurrence, late (beyond 90 d) complications, and stoma-free survival. Surveillance followed National Comprehensive Cancer Network guidelines, with pelvic magnetic resonance imaging (MRI) at 3 years to assess for pelvic sidewall recurrence when possible. Kaplan–Meier analysis assessed oncologic outcomes. Results: One hundred patients underwent taTME for tumors at a median of 5.8 cm from the anal verge, with intersphincteric resection in 36% and handsewn anastomosis in 54%. Median follow-up was 50.9 months. Late complications occurred in 32 patients, including 21 severe (Clavien-Dindo ≥3). Late anastomotic complications occurred in 5 patients; one required surgical revision. Estimated 3-year overall survival, cancer-specific survival, and disease-free survival were 93.7%, 96.6%, and 84.6%, respectively. Distant recurrence occurred in 15 patients (median: 17.6 months), most commonly in the lung and liver. Locoregional recurrence occurred in 2 patients. Preoperative N stage, lymph node yield, tumor deposits, and perineural invasion were associated with recurrence. Among 100 patients diverted at taTME, 97% were stoma-free at 3 years; 4 patients later underwent secondary diversion. Conclusions: Three-year outcomes of this multicenter trial support the safety and efficacy of taTME in resectable mid and low rectal tumors, with outcomes comparable to contemporary studies. Longer-term oncologic and functional outcomes are needed.

Abstract Background Global data demonstrate an inverse relationship between hospital ileoanal pouch volume and adverse outcomes, highlighting the need for quality metrics for this technically demanding procedure.1-4 Currently, there are no standardised quality indicators to define high-quality pouch surgery. This study aimed to establish international consensus on key performance indicators (KPIs) in pouch surgery. Methods A modified Delphi process was conducted among an international, multidisciplinary panel of experts. Participants were identified through professional networks, literature review, and direct email invitation; additional participants recruited via a snowball sampling approach over one month. Candidate KPIs were generated from literature review and expert input across 5 domains. Each item was rated on a 9-point Likert scale (1 = not important, 9 = critically important); consensus was predefined as ≥ 80% of respondents rating an item 7–9. Items not reaching consensus were re-rated in a second round following anonymized group feedback. Results Round 1 included 312 participants from 37 countries. Demographics (Table 1): 53% were age 45 years, 35.2% were female, and included surgeons (68.6%) and gastroenterologists (31.1%). Most (76.6%) practice at academic or university hospitals, with a median of 11 (5–17) years in practise; 78.9% perform >1 pouchoscopy per month, and 39.5% of surgeons perform 5 pouches/year. Respondents’ regions included North America (51%), Europe (26%), Oceania (9%), Asia (6%), Latin America (4%), and the Middle East/Africa (4%). Seven (18%) countries (Denmark, Lithuania, Malaysia, Norway, United Arab Emirates, Sweden, and Switzerland) reported pouch surgery is already centralised, while 70.6% agreed pouch centralisation should be implemented. Cost/logistics and professional autonomy were the most important barriers to centralisation, whereas capacity and training exposure were least important. Overall, 37/59 (62.7%) candidate KPIs reached consensus after Round 1. The Round 2 response rate was 61%, and 2 additional KPIs reached consensus (preop ileitis and long-term risk of pouchitis). Additionally, 14 of 25 (56%) informed consent items reached consensus, and 64% of respondents felt informed consent for pouch surgery requires 2 or more office visits. Consensus items were used to populate a KPIPS Checklist (Figure 1). Conclusion Through an international Delphi process, the KPIPS study identified a consensus-derived set of key performance indicators to measure quality in pouch surgery. These quality metrics provide a foundation for benchmarking outcomes and represent a critical step towards centralization and the development of designated pouch centres of excellence to improve global standards of care for pouch patients. References: 1. Worley GHT, Fearnhead NS, Brown SR, et al. Review of current practice and outcomes following ileoanal pouch surgery: Lessons learned from the ileoanal pouch registry and the 2017 ileoanal pouch report. Colorectal Dis 2018;20:913–22. 2. Giddings HL, Yang PF, Steffens D, Solomon MJ, Ng KS. Influence of hospital-level and surgeon factors on the outcomes after ileo-anal pouch surgery for inflammatory bowel disease: Systematic review. Br J Surg 2024;111. 3. Hoang CM, Maykel JA, Davids JS, et al. Distribution of elective ileal pouch-anal anastomosis cases for ulcerative colitis: A study utilizing the university health system consortium database. J Gastrointest Surg 2020;24:2613–9. 4. Moojen TB, Visser E, Reijntjes MA, et al. One-year stoma-free survival of ileoanal pouches for uc in european centers: The miracle project. Ann Surg Open 2025;6:e596. Conflict of interest: Prof. Holubar, Stefan: No conflict of interest Soop, Mattias: No conflict of interest Poskus, Tomas: No conflict of interest Neary, Peter: No conflict of interest Uchino, Tairin: No conflict of interest Yang, Song-soo: No conflict of interest Adamina, Michel: No conflict of interest Avellaneda, Nicolas Luis: No conflict of interest Barnes, Edward: No conflict of interest Brouquet, Antoine: No conflict of interest Brown, Steven Ross: No conflict of interest De Buck Van Overstraeten, Anthony: No conflict of interest Buskens, Christianne J.: No conflict of interest Chiorean, Michael: No conflict of interest Clark, David: No conflict of interest Cohen, Benjamin: No conflict of interest El Ouali, Sara: No conflict of interest Faiz, Omar Darius: No conflict of interest Fichera, Alessandro: No conflict of interest Hahnloser, Dieter: No conflict of interest Hancock, Laura: No conflict of interest Herfarth, Hans: No conflict of interest Johnston, Michael: No conflict of interest Kayal, Maia: No conflict of interest Laharie, David: No conflict of interest Liberman, Sender: No conflict of interest Loftus, Jr, Edward: No conflict of interest Moeslein, Gabriela: No conflict of interest Myrelid, Pär: No conflict of interest Poylin, Vitaliy: No conflict of interest Qazi, Taha: No conflict of interest Raffals, Laura: No conflict of interest Rubin, David T.: No conflict of interest Spinelli, Antonino: No conflict of interest Steinhagen, Emily: No conflict of interest Tozer, Philip: No conflict of interest Verstockt, Bram: No conflict of interest Warusavitarne, Janindra: No conflict of interest Wexner, Steven: No conflict of interest Winter, Desmond: No conflict of interest

Abstract Background Patients with Crohn disease (CD) face an elevated risk of developing small bowel adenocarcinoma (SBA), a malignancy characterized by late-stage diagnosis and poor prognosis. In this study we aimed to characterize surgical management and oncologic outcomes for CD-associated SBA. Methods A retrospective review was conducted across 3 tertiary IBD centers, analyzing 99 patients with CD who underwent surgery for SBA between 1992 and 2025. Data included patient demographics, CD history, surgical details, and oncologic outcomes. Results The median time from CD diagnosis to SBA was 25 years. The SBA diagnosis was incidental in 74.8% of cases, discovered during surgery for other complications. Tumors were predominantly located in the ileum (80.8%) and showed aggressive features: 56.6% were poorly differentiated (grade 3), and 85.9% were pathologically advanced (T3/T4 on TNM staging). Nodal involvement was present in 45.5% of patients, and 18.2% had distant metastases at diagnosis. A complete (R0) resection was achieved in 90.9% of surgeries, with a 30-day morbidity rate of 26.3%. After a median follow-up of 36 months, the distant recurrence rate was 28.3%, and overall mortality was 27.3% (18.2% cancer related). Conclusion In patients with long-standing CD, SBA is typically an incidental diagnosis made at an advanced stage. While high rates of complete surgical resection are possible, the prognosis remains guarded due to aggressive tumor biology and high recurrence rates. These findings highlight a critical need for improved risk stratification to guide surveillance and for the development of evidence-based adjuvant treatment strategies.

Abstract Disclosure: D.S. Ali: None. Z. Chung: None. L. Kamel: None. S. Björnsdottir: Shire. B.L. Clarke: Shire, Takeda, Ascendis, Calcilytix. S. Hahner: None. L.C. Hofbauer: Amgen Inc, Ascendis, UCB, Ascendis, Amolyte. P. Houillier: None. S.W. Ing: Amgen Inc, Radius Health, Inc, Takeda, AscendAlexion, Amolyt, Ascendis, Calcilytix, Kyowa Kirin. M.A. Levine: Takeda, Amolyt, Calcilytix. M. Mannstadt: Takeda, Amolyt, Calcilytix. L. Rejnmark: Takeda, Amolyt, Ascendis, Calcilytix. D.M. Shoback: Amolyt, Ascendis, member of the advisory board (PARADIGHM). M. Brandi: Takeda, Eli Lilly & Company, Calcilytix, Kyowa Kirin, UCB, Abiogen, Alexion, Amolyt, Amorphical, Bruno Farmaceutici, CoGeDi, Echolight. A.A. Khan: Takeda, Amgen Inc, Alexion, Ascendis, Amolyt, Calcilytix. Background: Hypoparathyroidism (HypoPT) is a rare endocrine disorder that requires close evaluation and follow up during pregnancy to minimize maternal and fetal complications. The primary objectives of this study are to evaluate the use of rhPTH (1-84) during pregnancy by analyzing data from the PARADIGHM disease registry, and to compare maternal and neonatal outcomes among patients who continued PTH therapy during pregnancy versus those on conventional therapy (CT). Methods: We performed a retrospective analysis of data in the PARADIGHM registry. Maternal and neonatal outcomes in women treated with rhPTH (1-84) were compared to women who received CT. Results: We analyzed 39 pregnancies of 32 women. Of those, 4 women (6 pregnancies) used rhPTH (1-84) either before or during pregnancy and 28 women (33 pregnancies) continued CT during pregnancy. The mean (SD) maternal age at enrollment was 31.7 (5.6) years. Postsurgical HypoPT was the most common etiology (68.8%). The mean gestational age at delivery was 36 (2.4) weeks (PTH-treated) vs 38.3 (3.3) weeks (CT) (p=0.162). Preterm delivery rates were higher in the PTH-treated group (50% vs. 27%, p=0.591), but this was not statistically significant. Two women had pre-eclampsia, one in each group (PTH-treated and CT). In the PTH-treated group, one pregnancy resulted in a stillbirth, and one infant was born with congenital anomalies (16.7% each). Conclusions: The safety of rhPTH (1-84) use in pregnancy cannot be determined at this time. The PTH-treated group exhibited trends towards higher rates of preterm delivery, but the rates of stillbirth, and congenital anomalies were low and comparable in both groups of women. Larger studies are necessary to determine the optimal approach to manage women with HypoPT during pregnancy. Presentation: Sunday, July 13, 2025

Background: Periarticular local infiltration analgesia has become an important mainstay of multimodal analgesia after elective total hip arthroplasty (THA). However, the role of novel motor-sparing fascial plane blocks—with or without periarticular local infiltration analgesia—has not been fully elucidated for patients undergoing THA. The authors conducted a network meta-analysis evaluating the relative analgesic effectiveness of motor-sparing fascial plane blocks (quadratus lumborum, erector spinae, and pericapsular nerve group blocks) and periarticular local infiltration analgesia for adult patients undergoing THA. Methods: Randomized trials examining single-injection quadratus lumborum, erector spinae, or pericapsular nerve group blocks, or periarticular local infiltration analgesia, for THA were sought. The primary outcome was area under the curve (AUC) rest pain scores during the period from 0 to 24 h. Secondary outcomes included rest pain scores at 0, 6, 12, and 24 h; postoperative function at 6, 12, and 24 h; analgesic consumption at 0 to 24 h; incidence of opioid-related side effects; and incidence of block-related complications. Network meta-analysis was performed using a frequentist approach. Results: A total of 44 trials (3,579 patients) evaluating the quadratus lumborum block, erector spinae block, pericapsular nerve group block, or periarticular local infiltration analgesia for THA were considered. Network meta-analysis was used to derive the probability of each intervention being the most effective as compared to the others (P score). For AUC 0 to 24 h rest pain, periarticular local infiltration analgesia was the most effective intervention, as demonstrated by a P score of 89%. For postoperative analgesic consumption, the quadratus lumborum block was the most effective intervention, with a P score of 88%. This was followed by the pericapsular nerve group block (74%), the erector spinae block (38%), and periarticular local infiltration analgesia (42%). Conclusions: Periarticular local infiltration analgesia alone provides the most consistent improvements in postoperative rest pain, analgesic consumption, and functional recovery after THA. The addition of a quadratus lumborum block or pericapsular nerve group block to periarticular local infiltration may further improve analgesic outcomes.

BACKGROUND: Data registries lack a definitive classification system that distinguishes different locations of colon cancer from one another. OBJECTIVE: To establish an international consensus on the definition of primary colon cancer segment locations. DESIGN: Between December 2022 and June 2023, Delphi survey study was conducted to seek opinions from relevant international experts and eventually develop a consensus definition of each colon cancer segment. SETTING: Three-round online-based Delphi survey study. INTERVENTIONS: Online survey included 17 questions. In the first two rounds, participating experts were asked to rank each statement on a scale of 1–9 (9 is the most relevant). Consensus statements and definitions were revised according to results, obtaining a consensus score of 7–9. During the third round and online meeting, definitions and statements reached a moderate or high consensus(above 4 in more than 70% of participants) were included. MAIN OUTCOME AND MEASURE: Primary goal of our project was focused on precisely localizing the specific segment affected by primary colon cancer, rather than to identify surgical treatment or type of resection needed for particular segment. RESULTS: The first round included 331 experts, 301 (91%) completed the second round, and 295 (98%) completed the final round. Experts strongly supported the use of a “10 cm rule” to describe colon cancer sites at the flexures and anatomical landmarks for other segments. Regarding the definition of rectosigmoid cancer, experts from America and Europe reached a high consensus that the term rectosigmoid as a colon cancer location must be abolished in contrast to experts from Asia. Description of cancers overlapping segments achieved a consensus of 64%. LIMITATIONS: Subjective decisions are based on individual expert clinical experience. CONCLUSIONS: This Delphi survey, the first internationally conducted consensus study, achieved a remarkable level of consensus among a panel of global experts. Ambiguity still exists regarding overlapping lesions. See Video Abstract .

AbstractBackgroundInflammatory bowel disease (IBD) affects more than 10 million people worldwide. Men and women are equally affected by Crohn's disease (CD). It has been shown that patients with CD are at an increased risk of a colorectal cancer (CRC) diagnosis and CRC‐related mortality. During the last two decades, biological therapies have revolutionized the treatment of CD. There are no current studies investigating the prevalence of CRC in patients with CD in the era of biological therapy and the possible features of patients with CD who are at high risk of developing CRC.AimWe aim to assess the prevalence of CRC, risk factors and profile of CRC in patients with CD receiving biological treatment compared with those who are not under biological therapy and the impact of CD‐associated colorectal strictures on CRC development. The study hypothesis is that the use of biological therapy in the control of CD activity may decrease the risk of developing CRC.Study design and settingAn international, retrospective, snapshot of the prevalence of CRC in patients with CD, reported according to the SPIRIT guidelines. The study will involve centres that hold regular IBD multidisciplinary team meetings and have both IBD colorectal surgeons and gastroenterologists. Each participating centre will provide a local consultant lead and a local trainee lead. Data will be collected within a 2‐year recruitment period (January 2017–January 2019).Study populationAdult patients who presented with CD during the study period. Patients with an incidental diagnosis of CD during evaluation for CRC will be excluded.Statistical planBaseline patient characteristics will be summarized using the appropriate descriptive statistics. Univariable, multivariable and Cox regression models will be used to identify factors significantly associated with CRC. For noncontinuous variables a comparison between the subgroups will be carried out using the chi‐square test corrected by Fisher's exact test if appropriate. A p‐value of <0.05 will be considered statistically significant.Data storageData will be stored on a secured server, pin‐code protected according to the local data management agreement.

Abstract Disclosure: S.W. Ing: Advisory Board Member; Self; Ultragenyx, Amolyt. Grant Recipient; Self; Alexion Pharmaceuticals, Inc.. Research Investigator; Self; BridgeBio Pharma, Takeda, Amolyt, Radius Health, Inc, Ultragenyx. P. Harmatz: Research Investigator; Self; BridgeBio Pharma. S. Mora: Research Investigator; Self; BridgeBio Pharma. E.A. Imel: Research Investigator; Self; BridgeBio Pharma. P.J. Tebben: Research Investigator; Self; BridgeBio Pharma. M.L. Warren: Research Investigator; Self; BridgeBio Pharma, Ascendis, Amolyt. Speaker; Self; Ascendis. N. Ma: Research Investigator; Self; Calcilytix Therapeutics, Ultragenyx, Inozyme. Other; Self; Up To Date. A.A. Khan: Research Investigator; Self; BridgeBio Pharma, Ascendis. A. Palermo: Research Investigator; Self; BridgeBio Pharma. B. Decallonne: Research Investigator; Self; BridgeBio Pharma. S. Lemoine: Research Investigator; Self; BridgeBio Pharma, Kyowa Kirin. G. Mantovani: Research Investigator; Self; BridgeBio Pharma. A. Linglart: Consulting Fee; Self; Alexion, Novo Nordisk, Merck, Pfizer, Inc.. Research Investigator; Self; BridgeBio Pharma, Kyowa Kirin. H. Wasserman: Research Investigator; Self; BridgeBio Pharma. A.P. Barbosa: Research Investigator; Self; BridgeBio Pharma. C. Cardot-bauters: Research Investigator; Self; BridgeBio Pharma. M. Roberts: Employee; Self; BridgeBio Pharma. A. Mathew: Employee; Self; BridgeBio Pharma. S. Adler: Employee; Self; BridgeBio Pharma. M.C. Zillikens: Research Investigator; Self; BridgeBio Pharma. R.J. Clifton-Bligh: Consulting Fee; Self; Ipsen, Kyowa Kirin, Amgen Inc, Eisai. Research Investigator; Self; BridgeBio Pharma. L. Rejnmark: Research Investigator; Self; BridgeBio Pharma, Ascendis, Amolyt, Takeda, Kyowa Kirin. Autosomal dominant hypocalcemia type 1 (ADH1), caused by gain-of-function calcium-sensing receptor gene (CASR) variants, is characterized by low parathyroid hormone (PTH) concentrations, hypocalcemia, hypercalciuria, hyperphosphatemia and hypomagnesemia. While a rare disease, ADH1 is one of the more frequently identified causes of genetic hypoparathyroidism. Conventional therapy includes calcium (Ca) and/or active vitamin D, but this regimen incompletely corrects the hypocalcemia and is associated with persistent hypercalciuria, which may result in renal complications including nephrocalcinosis (NC), nephrolithiasis (NL), and chronic kidney disease (CKD). The CLARIFY disease monitoring study [NCT05227287] is a global, multicenter, longitudinal study to understand disease burden, management, and progression in children and adults with ADH1 over a 5-year period. Here we report data on the characteristics of adult participants at study entry. As of November 2023, 45 adults (≥18 years) with ADH1 were enrolled, with a mean±SD age of 42.1±16.5 years (range 18-80). The mean±SD age of a hypocalcemia diagnosis was 19.1±19.1 years, while the mean±SD age for a diagnosis of ADH1 was 28.2±20.6 years. As reported on medical history, in decreasing order of prevalence, 36% (16) had NC, 22% (10) had intracranial calcifications, 11% (5) had history of seizures, 11% (5) had CKD, 9% (4) had cataracts, 7% (3) had NL, and 4% (2) had undergone renal transplant. Treatment data were available for 43 participants and included the following: 74% (32) Ca and active vitamin D, 9% (4) Ca alone, 9% (4) active vitamin D alone, 37% (16) magnesium, 33% (14) thiazide diuretics, 26% (11) potassium, 7% (3) phosphate binder, 7% (3) PTH, and 5% (2) no treatment. Mean±SD fasting values collected prior to conventional therapy dose are presented. PTH concentrations (10.1±8.2 pg/mL [nl 15-65]) and albumin-corrected calcium ([cCa]=7.5±1.0 mg/dL [nl 8.5-10.5]) were low. Despite the low mean cCa, the mean 24-hr urine calcium was elevated (268±183 mg/d, [nl &lt;250 women, &lt;300 men]). Blood phosphate was 4.8±0.8 mg/dL [nl 2.5-4.8] while blood magnesium was 1.8±0.2 mg/dL [nl 1.8-2.4]. 25-OH vitamin D was 35.0±13.5 ng/mL [nl 30-80]. Renal function as assessed by CKD-EPIcr_R showed eGFR of 86±23 mL/min/1.73m² (range 36-123). This study represents the largest cohort of adults with ADH1 described to date. These data highlight variability in therapeutic approaches in a real-world setting with some participants receiving up to 6 different medications/supplements. Despite being followed in expert centers, and treated with available therapies, patients on average have low cCa with relatively high 24-hr urine calcium excretion. The CLARIFY study provides an opportunity to better understand the progression and burden of disease in participants with ADH1. Presentation: 6/3/2024