AlPaCas: allele-specific CRISPR gene editing through a protospacer-adjacent-motif (PAM) approach.

Gene therapy of dominantly inherited genetic diseases requires either the selective disruption of the mutant allele or the editing of the specific mutation. The CRISPR-Cas system holds great potential for the genetic correction of single nucleotide variants (SNVs), including dominant mutations. However, distinguishing between single-nucleotide variations in a pathogenic genomic context remains challenging. The presence of a PAM in the disease-causing allele can guide its precise targeting, preserving the functionality of the wild-type allele. The AlPaCas (Aligning Patients to Cas) webserver is an automated pipeline for sequence-based identification and structural analysis of SNV-derived PAMs that satisfy this demand. When provided with a gene/SNV input, AlPaCas can: (i) identify SNV-derived PAMs; (ii) provide a list of available Cas enzymes recognizing the SNV (s); (iii) propose mutational Cas-engineering to enhance the selectivity towards the SNV-derived PAM. With its ability to identify allele-specific genetic variants that can be targeted using already available or engineered Cas enzymes, AlPaCas is at the forefront of advancements in genome editing. AlPaCas is open to all users without a login requirement and is freely available at https://schubert.bio.uniroma1.it/alpacas.

Transgenic Epidermal Cultures for Junctional Epidermolysis Bullosa - 5-Year Outcomes.

Inherited junctional epidermolysis bullosa is a severe genetic skin disease that leads to epidermal loss caused by structural and mechanical fragility of the integuments. There is no established cure for junctional epidermolysis bullosa. We previously reported that genetically corrected autologous epidermal cultures regenerated almost an entire, fully functional epidermis on a child who had a devastating form of junctional epidermolysis bullosa. We now report long-term clinical outcomes in this patient. (Funded by POR FESR 2014-2020 - Regione Emilia-Romagna and others.).

An ultrasound multiparametric method to quantify liver fat using magnetic resonance as standard reference.

BACKGROUND & AIMS: There is an unmet need for a reliable and reproducible non-invasive measure of fatty liver content (FLC) for monitoring steatotic liver disease in clinical practice. Sonographic FLC assessment is qualitative and operator-dependent, and the dynamic quantification range of algorithms based on a single ultrasound (US) parameter is unsatisfactory. This study aims to develop and validate a new multiparametric algorithm based on B-mode images to quantify FLC using Magnetic Resonance (MR) values as standard reference. METHODS: Patients with elevated liver enzymes and/or bright liver at US (N = 195) underwent FLC evaluation by MR and by US. Five US-derived quantitative features [attenuation rate(AR), hepatic renal-ratio(HR), diaphragm visualization(DV), hepatic-portal-vein-ratio(HPV), portal-vein-wall(PVW)] were combined by mixed linear/exponential regression in a multiparametric model (Steatoscore2.0). One hundred and thirty-four subjects were used for training and 61 for independent validations; score-computation underwent an inter-operator reproducibility analysis. RESULTS: The model is based on a mixed linear/exponential combination of 3 US parameters (AR, HR, DV), modelled by 2 equations according to AR values. The computation of FLC by Steatoscore2.0 (mean ± std, 7.91% ± 8.69) and MR (mean ± std, 8.10% ± 10.31) is highly correlated with a low root mean square error in both training/validation cohorts, respectively (R = 0.92/0.86 and RMSE = 5.15/4.62, p < .001). Steatoscore2.0 identified patients with MR-FLC≥5%/≥10% with sensitivity = 93.2%/89.4%, specificity = 86.1%/95.8%, AUROC = 0.958/0.975, respectively and correlated with MR (R = 0.92) significantly (p < .001) better than CAP (R = 0.73). CONCLUSIONS: Multiparametric Steatoscore2.0 measures FLC providing values highly comparable with MR. It is reliable, inexpensive, easy to use with any US equipment and qualifies to be tested in larger, prospective studies as new tool for the non-invasive screening and monitoring of FLC.

Clinical outcomes and complications of S53P4 bioactive glass in chronic osteomyelitis and septic non-unions: a retrospective single-center study.

INTRODUCTION: Dead space management following debridement surgery in chronic osteomyelitis or septic non-unions is one of the most crucial and discussed steps for the success of the surgical treatment of these conditions. In this retrospective clinical study, we described the efficacy and safety profile of surgical debridement and local application of S53P4 bioactive glass (S53P4 BAG) in the treatment of bone infections. METHODS: A consecutive single-center series of 38 patients with chronic osteomyelitis (24) and septic non-unions (14), treated with bioactive glass S53P4 as dead space management following surgical debridement between May 2015 and November 2020, were identified and evaluated retrospectively. RESULTS: Infection eradication was reached in 22 out of 24 patients (91.7%) with chronic osteomyelitis. Eleven out of 14 patients (78.6%) with septic non-union achieved both fracture healing and infection healing in 9.1 ± 4.9 months. Three patients (7.9%) developed prolonged serous discharge with wound dehiscence but healed within 2 months with no further surgical intervention. Average patient follow-up time was 19.8 months ± 7.6 months. CONCLUSION: S53P4 bioactive glass is an effective and safe therapeutic option in the treatment of chronic osteomyelitis and septic non-unions because of its unique antibacterial properties, but also for its ability to generate a growth response in the remaining healthy bone at the bone-glass interface.

Expanding SPG18 clinical spectrum: autosomal dominant mutation causes complicated hereditary spastic paraplegia in a large family.

BACKGROUND: SPG18 is caused by mutations in the endoplasmic reticulum lipid raft associated 2 (ERLIN2) gene. Autosomal recessive (AR) mutations are usually associated with complicated hereditary spastic paraplegia (HSP), while autosomal dominant (AD) mutations use to cause pure SPG18. AIM: To define the variegate clinical spectrum of the SPG18 and to evaluate a dominant negative effect of erlin2 (encoded by ERLIN2) on oligomerization as causing differences between AR and AD phenotypes. METHODS: In a four-generation pedigree with an AD pattern, a spastic paraplegia multigene panel test was performed. Oligomerization of erlin2 was analyzed with velocity gradient assay in fibroblasts of the proband and healthy subjects. RESULTS: Despite the common p.V168M mutation identified in ERLIN2, a phenoconversion to amyotrophic lateral sclerosis (ALS) was observed in the second generation, pure HSP in the third generation, and a complicated form with psychomotor delay and epilepsy in the fourth generation. Erlin2 oligomerization was found to be normal. DISCUSSION: We report the first AD SPG18 family with a complicated phenotype, and we ruled out a dominant negative effect of V168M on erlin2 oligomerization. Therefore, our data do not support the hypothesis of a relationship between the mode of inheritance and the phenotype, but confirm the multifaceted nature of SPG18 on both genetic and clinical point of view. Clinicians should be aware of the importance of conducting an in-depth clinical evaluation to unmask all the possible manifestations associated to an only apparently pure SPG18 phenotype. We confirm the genotype-phenotype correlation between V168M and ALS emphasizing the value of close follow-up.

Orthoplastic Management of Lower Limb Traumas: A Retrospective Study on Polytraumas Versus Isolated Injuries.

BACKGROUND: Open fractures of the lower limb represent a common challenge for trauma centers. Even where national guidelines are available, these standards are frequently missing. Our study evaluates the influence of polytrauma on the adherence to the timing and management required in an orthoplastic approach. PATIENTS AND METHODS: A retrospective review was performed on 36 patients affected by a Gustilo-Anderson grade IIIA, IIIB, or IIIC fracture of the lower limb between 2018 and 2022. Data related to patient management were analyzed: time to the first evaluation by a plastic surgeon, time to soft tissue coverage, time to definitive osteosynthesis, days in intensive care unit (ICU), days of hospitalization, and total cost of hospital stay. Patient satisfaction was evaluated through the administration of 2 questionnaires: the Enneking and the Foot Function Index (FFI). RESULTS: In 23 patients (63.9%), a soft tissue reconstruction was required. Of these, 13 were polytraumas (PT) (56.5%) and 10 were affected by an isolated lower limb fracture (ILLF) (43.5%). The median time to wound excision was 7.0 days (IQR, 0-16.0) in the PT group and 12.5 days (IQR, 1-41.0) in the ILLF group, whereas the mean time to soft tissue coverage was 15.0 days (IQR, 4.0-17.0) in the PT group and 38.0 days (IQR, 25.0-65.0) in the ILLF group. Mean time to definitive fixation was 33.0 days (IQR, 6.5-70.0) in the PT group and 16.5 days (IQR, 3.0-26.0) in the ILLF group. Statistically significant difference was reported on mean time to soft tissue coverage, whereas not relevant differences were reported on mean time to plastic surgeon involvement, first debridement, definitive fixation, days of hospitalization, costs, and Enneking and FFI score. CONCLUSION: This is the first study comparing the effectiveness of the orthoplastic approach between isolated lower limb fractures and polytraumas. According to our study, open lower limb fracture management is paradoxically more effective in polytraumas rather than in isolated injuries because a multidisciplinary approach is mandatory in severely injured and compromised patients.

Response to "Letter to the Editor: The Promise and Pitfalls of AI-Generated Anatomical Images: Evaluating Midjourney for Aesthetic Surgery Applications".

This response letter answers a query regarding our study on the use of the Midjourney app in aesthetic surgery. The original study questioned the utility of Midjourney in enhancing surgical skills, patient understanding, and communication effectiveness. The response highlights the challenges and potential of AI in medical visualization, advocating for meticulous development and evaluation. It stresses the importance of the scientific community's role in educating the public about the reliability and appropriate use of new technologies to avoid misconceptions and ensure the safe integration of AI in advancing medical fields like aesthetic surgery. The authors advocate for ongoing research and thoughtful application of AI tools, acknowledging both their benefits and limitations in the medical context.Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Regeneration of the entire human epidermis using transgenic stem cells.

Junctional epidermolysis bullosa (JEB) is a severe and often lethal genetic disease caused by mutations in genes encoding the basement membrane component laminin-332. Surviving patients with JEB develop chronic wounds to the skin and mucosa, which impair their quality of life and lead to skin cancer. Here we show that autologous transgenic keratinocyte cultures regenerated an entire, fully functional epidermis on a seven-year-old child suffering from a devastating, life-threatening form of JEB. The proviral integration pattern was maintained in vivo and epidermal renewal did not cause any clonal selection. Clonal tracing showed that the human epidermis is sustained not by equipotent progenitors, but by a limited number of long-lived stem cells, detected as holoclones, that can extensively self-renew in vitro and in vivo and produce progenitors that replenish terminally differentiated keratinocytes. This study provides a blueprint that can be applied to other stem cell-mediated combined ex vivo cell and gene therapies.

The steep uphill path leading to ex vivo gene therapy for genodermatoses.

Cell therapy, gene therapy, and tissue engineering have the potential to revolutionize the field of regenerative medicine. In particular, gene therapy is understood as the therapeutical correction of mutated genes by addition of a correct copy of the gene or site-specific gene modifications. Gene correction of somatic stem cells sustaining renewing tissues is critical to ensure long-term clinical success of ex vivo gene therapy. To date, remarkable clinical outcomes arose from combined ex vivo cell and gene therapy of different genetic diseases, such as immunodeficiencies and genodermatoses. Despite the efforts of researchers around the world, only a few of these advanced approaches have yet made it to routine therapy. In fact, gene therapy poses one of the greatest technical challenges in modern medicine, spanning safety and efficacy issues, regulatory constraints, registration and market access, all of which need to be addressed to make the therapy available to patients with rare disease. In this review, we survey some of the main challenges in the development of combined cell and gene therapy of genetic skin diseases.

Fighting the Huntington's Disease with a G-Quadruplex-Forming Aptamer Specifically Binding to Mutant Huntingtin Protein: Biophysical Characterization, In Vitro and In Vivo Studies.

A set of guanine-rich aptamers able to preferentially recognize full-length huntingtin with an expanded polyglutamine tract has been recently identified, showing high efficacy in modulating the functions of the mutated protein in a variety of cell experiments. We here report a detailed biophysical characterization of the best aptamer in the series, named MS3, proved to adopt a stable, parallel G-quadruplex structure and show high nuclease resistance in serum. Confocal microscopy experiments on HeLa and SH-SY5Y cells, as models of non-neuronal and neuronal cells, respectively, showed a rapid, dose-dependent uptake of fluorescein-labelled MS3, demonstrating its effective internalization, even in the absence of transfecting agents, with no general cytotoxicity. Then, using a well-established Drosophila melanogaster model for Huntington's disease, which expresses the mutated form of human huntingtin, a significant improvement in the motor neuronal function in flies fed with MS3 was observed, proving the in vivo efficacy of this aptamer.

Truncated Analogues of a G-Quadruplex-Forming Aptamer Targeting Mutant Huntingtin: Shorter Is Better!

Two analogues of the MS3 aptamer, which was previously shown to have an exquisite capability to selectively bind and modulate the activity of mutant huntingtin (mHTT), have been here designed and evaluated in their physicochemical and biological properties. Featured by a distinctive propensity to form complex G-quadruplex structures, including large multimeric aggregates, the original 36-mer MS3 has been truncated to give a 33-mer (here named MS3-33) and a 17-mer (here named MS3-17). A combined use of different techniques (UV, CD, DSC, gel electrophoresis) allowed a detailed physicochemical characterization of these novel G-quadruplex-forming aptamers, tested in vitro on SH-SY5Y cells and in vivo on a Drosophila Huntington's disease model, in which these shorter MS3-derived oligonucleotides proved to have improved bioactivity in comparison with the parent aptamer.

Epigenetic and metabolic regulation of epidermal homeostasis.

Continuous exposure of the skin to environmental, mechanical and chemical stress necessitates constant self-renewal of the epidermis to maintain its barrier function. This self-renewal ability is attributed to epidermal stem cells (EPSCs), which are long-lived, multipotent cells located in the basal layer of the epidermis. Epidermal homeostasis - coordinated proliferation and differentiation of EPSCs - relies on fine-tuned adaptations in gene expression which in turn are tightly associated with specific epigenetic signatures and metabolic requirements. In this review, we will briefly summarize basic concepts of EPSC biology and epigenetic regulation with relevance to epidermal homeostasis. We will highlight the intricate interplay between mitochondrial energy metabolism and epigenetic events - including miRNA-mediated mechanisms - and discuss how the loss of epigenetic regulation and epidermal homeostasis manifests in skin disease. Discussion of inherited epidermolysis bullosa (EB) and disorders of cornification will focus on evidence for epigenetic deregulation and failure in epidermal homeostasis, including stem cell exhaustion and signs of premature ageing. We reason that the epigenetic and metabolic component of epidermal homeostasis is significant and warrants close attention. Charting epigenetic and metabolic complexities also represents an important step in the development of future systemic interventions aimed at restoring epidermal homeostasis and ameliorating disease burden in severe skin conditions.

Gentamicin induces LAMB3 nonsense mutation readthrough and restores functional laminin 332 in junctional epidermolysis bullosa.

Herlitz junctional epidermolysis bullosa (H-JEB) is an incurable, devastating, and mostly fatal inherited skin disease for which there is only supportive care. H-JEB is caused by loss-of-function mutations in LAMA3, LAMB3, or LAMC2, leading to complete loss of laminin 332, the major component of anchoring filaments, which mediate epidermal-dermal adherence. LAMB3 (laminin ß3) mutations account for 80% of patients with H-JEB, and ∼95% of H-JEB-associated LAMB3 mutations are nonsense mutations leading to premature termination codons (PTCs). In this study, we evaluated the ability of gentamicin to induce PTC readthrough in H-JEB laminin ß3-null keratinocytes transfected with expression vectors encoding eight different LAMB3 nonsense mutations. We found that gentamicin induced PTC readthrough in all eight nonsense mutations tested. We next used lentiviral vectors to generate stably transduced H-JEB cells with the R635X and C290X nonsense mutations. Incubation of these cell lines with various concentrations of gentamicin resulted in the synthesis and secretion of full-length laminin ß3 in a dose-dependent and sustained manner. Importantly, the gentamicin-induced laminin ß3 led to the restoration of laminin 332 assembly, secretion, and deposition within the dermal/epidermal junction, as well as proper polarization of α6ß4 integrin in basal keratinocytes, as assessed by immunoblot analysis, immunofluorescent microscopy, and an in vitro 3D skin equivalent model. Finally, newly restored laminin 332 corrected the abnormal cellular phenotype of H-JEB cells by reversing abnormal cell morphology, poor growth potential, poor cell-substratum adhesion, and hypermotility. Therefore, gentamicin may offer a therapy for H-JEB and other inherited skin diseases caused by PTC mutations.

Extrameningeal solitary fibrous tumors-surgery alone or surgery plus perioperative radiotherapy: A retrospective study from the global solitary fibrous tumor initiative in collaboration with the Sarcoma Patients EuroNet.

BACKGROUND: Solitary fibrous tumor (SFT) is a rare mesenchymal malignancy. Although surgery is potentially curative, the local relapse risk is high after marginal resections. Given the lack of prospective clinical trial data, the objective of the current study was to better define the role of perioperative radiotherapy (RT) in various SFT presentations by location. METHODS: This was retrospective study performed across 7 sarcoma centers. Clinical information was retrieved from all adult patients with extrameningeal, primary, localized SFT who were treated between 1990 and 2018 with surgery alone (S) compared with those who also received perioperative RT (S+RT). Differences in treatment characteristics between subgroups were tested using analysis of variance statistics and propensity score matching. Local control and overall survival rates were calculated from the start of treatment until progression or death from any cause. RESULTS: Of all 549 patients, 428 (78%) underwent S, and 121 (22%) underwent S+RT. The median follow-up was 52 months. After correction for mitotic count and surgical margins, S+RT was significantly associated with a lower risk of local progression (hazard ratio, 0.19: P = .029), an observation further confirmed by propensity score matching (P = .012); however, this association did not translate into an overall survival benefit. CONCLUSIONS: The results from this retrospective study investigating perioperative RT in patients with primary extrameningeal SFT suggest that combining RT with surgery in the management of this patient population is significantly associated with a reduced risk of local failures, especially in patients who have less favorable resection margins and in those who have tumors with a high mitotic count.

p63 control of desmosome gene expression and adhesion is compromised in AEC syndrome.

Ankyloblepharon, ectodermal defects, cleft lip/palate (AEC) syndrome is a rare autosomal dominant disorder caused by mutations in the p63 gene, essential for embryonic development of stratified epithelia. The most severe cutaneous manifestation of this disorder is the long-lasting skin fragility associated with severe skin erosions after birth. Using a knock-in mouse model for AEC syndrome, we found that skin fragility was associated with microscopic blistering between the basal and suprabasal compartments of the epidermis and reduced desmosomal contacts. Expression of desmosomal cadherins and desmoplakin was strongly reduced in AEC mutant keratinocytes and in newborn epidermis. A similar impairment in desmosome gene expression was observed in human keratinocytes isolated from AEC patients, in p63-depleted keratinocytes and in p63 null embryonic skin, indicating that p63 mutations causative of AEC syndrome have a dominant-negative effect on the wild-type p63 protein. Among the desmosomal components, desmocollin 3, desmoplakin and desmoglein 1 were the most significantly reduced by mutant p63 both at the RNA and protein levels. Chromatin immunoprecipitation experiments and transactivation assays revealed that p63 controls these genes at the transcriptional level. Consistent with reduced desmosome function, AEC mutant and p63-deficient keratinocytes had an impaired ability to withstand mechanical stress, which was alleviated by epidermal growth factor receptor inhibitors known to stabilize desmosomes. Our study reveals that p63 is a crucial regulator of a subset of desmosomal genes and that this function is impaired in AEC syndrome. Reduced mechanical strength resulting from p63 mutations can be alleviated pharmacologically by increasing desmosome adhesion with possible therapeutic implications.

A cellular disease model toward gene therapy of TGM1-dependent lamellar ichthyosis.

Lamellar ichthyosis (LI) is a chronic disease, mostly caused by mutations in the TGM1 gene, marked by impaired skin barrier formation. No definitive therapies are available, and current treatments aim at symptomatic relief. LI mouse models often fail to faithfully replicate the clinical and histopathological features of human skin conditions. To develop advanced therapeutic approaches, such as combined ex vivo cell and gene therapy, we established a human cellular model of LI by efficient CRISPR-Cas9-mediated gene ablation of the TGM1 gene in human primary clonogenic keratinocytes. Gene-edited cells showed complete absence of transglutaminase 1 (TG1) expression and recapitulated a hyperkeratotic phenotype with most of the molecular hallmarks of LI in vitro. Using a self-inactivating γ-retroviral (SINγ-RV) vector expressing transgenic TGM1 under the control of its own promoter, we tested an ex vivo gene therapy approach and validate the model of LI as a platform for pre-clinical evaluation studies. Gene-corrected TGM1-null keratinocytes displayed proper TG1 expression, enzymatic activity, and cornified envelope formation and, hence, restored proper epidermal architecture. Single-cell multiomics analysis demonstrated proviral integrations in holoclone-forming epidermal stem cells, which are crucial for epidermal regeneration. This study serves as a proof of concept for assessing the potential of this therapeutic approach in treating TGM1-dependent LI.

Applications of Deep Learning Algorithms to Ultrasound Imaging Analysis in Preclinical Studies on In Vivo Animals.

BACKGROUND AND AIM: Ultrasound (US) imaging is increasingly preferred over other more invasive modalities in preclinical studies using animal models. However, this technique has some limitations, mainly related to operator dependence. To overcome some of the current drawbacks, sophisticated data processing models are proposed, in particular artificial intelligence models based on deep learning (DL) networks. This systematic review aims to overview the application of DL algorithms in assisting US analysis of images acquired in in vivo preclinical studies on animal models. METHODS: A literature search was conducted using the Scopus and PubMed databases. Studies published from January 2012 to November 2022 that developed DL models on US images acquired in preclinical/animal experimental scenarios were eligible for inclusion. This review was conducted according to PRISMA guidelines. RESULTS: Fifty-six studies were enrolled and classified into five groups based on the anatomical district in which the DL models were used. Sixteen studies focused on the cardiovascular system and fourteen on the abdominal organs. Five studies applied DL networks to images of the musculoskeletal system and eight investigations involved the brain. Thirteen papers, grouped under a miscellaneous category, proposed heterogeneous applications adopting DL systems. Our analysis also highlighted that murine models were the most common animals used in in vivo studies applying DL to US imaging. CONCLUSION: DL techniques show great potential in terms of US images acquired in preclinical studies using animal models. However, in this scenario, these techniques are still in their early stages, and there is room for improvement, such as sample sizes, data preprocessing, and model interpretability.

Stairways to Advanced Therapies for Epidermolysis Bullosa.

Epidermolysis bullosa (EB) is a devastating genetic skin disease typified by a plethora of different phenotypes and ranking from severe, early lethal, to mild localized forms. Although there is no cure for EB, recent progress in pharmacology and molecular and cellular biology is boosting the development of new advanced therapeutic strategies. Here we will focus on two main categories of such therapies: (1) those aimed at controlling inflammation and inducing reepithelialization of the wounds, and (2) those, perhaps more challenging and ambitious, that aim to permanently regenerate a fully functional epidermis, which requires targeting of epidermal stem cells. In both cases, the genetic variants underlying the different EB forms and factors, such as genetic background, modifier genes, comorbidities, and lifestyle, all of which impinge on EB genotype-phenotype correlation, need to be defined.

Contemporary role of amputation for patients with extremity soft tissue sarcoma.

INTRODUCTION: limb-sparing surgery is the mainstream treatment for primary extremity soft tissue sarcoma (ESTS) at referral centers, following advances in surgical reconstructions and multimodal management. However, amputation is still needed in selected patients and has not yet been described for a ESTS cohort in a contemporary scenario. MATERIAL AND METHODS: consecutive patients who underwent surgery for primary ESTS from 2006 to 2018 were extracted from a prospectively collected database at our reference center. Patients receiving amputation for either primary tumor or local recurrence (LR) after limb-sparing surgery were selected for analysis. RESULTS: Among 1628 primary ESTS, 29 patients underwent primary amputation (1.8%), 22/1159 (1.9%) for upper limb and 7/469 (1.5%) for lower limb ESTS. Patients were mainly affected by grade III FNCLCC (89.6%) of notable dimension (median size 16 cm, IQR 10-24). 65.5% of patients received preoperative treatments (systemic or regional chemotherapy, radiotherapy or chemo-radiation). Secondary amputation for LR was performed after a median of 23 months in 16/1599 patients (1%). Median survival time was 16.2 and 29.6 months after primary or secondary amputation respectively. Factors prompting the need for a primary amputation were most often a combination of multifocal disease, bone invasion and pain or neurovascular bundle involvement and relevant comorbidities, mainly for grade III tumors in elderly patients. CONCLUSION: Contemporary rate of amputation for ESTS at a reference center is extremely low. Still, amputation is required in selected cases with advanced presentations, especially in elderly, frail patients.