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Charcot neuroarthropathy is a chronic, progressive condition of the skeletal system that affects some patients with diabetic neuropathy. It results in progressive destruction of bones of the foot and disorganisation of pedal joints and ligaments. Effective prevention and treatment for Charcot neuroarthropathy remain a challenge. Currently, there are no reliable repeatable markers to identify patients with diabetes who are at higher risk of developing Charcot neuroarthropathy. The pathogenesis underlying the development of Charcot neuroarthropathy also remains unclear. In this review, we provide an overview of the history, prevalence, symptoms, risk factors, diagnostics and treatment of Charcot neuroarthropathy. We also discuss the potential for OPG and RANKL gene variants to act as predictive markers for the development of Charcot neuroarthropathy. Finally, we summarise the latest research on the role of monocyte-to-osteoclast differentiation in the development of acute Charcot neuroarthropathy., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Objective: To report a case of neuroarthropathy in the tarsus and knee following rapid glycaemic normalisation in a female patient with type I diabetes., Methods: A retrospective review of case notes., Results: We describe the case of a female patient with type I diabetes who had developed a multifocal neuroarthropathy in only six months, probably due to a rapid glycaemic normalisation. The onset of this neuroarthropathy was not only fast but mostly multifocal affecting two levels of joints., Conclusion: The link between the onset of multifocal neuroarthropathy and the rapid correction of chronic hyperglycaemia is probably proven in our case. Patients with chronic hyperglycaemia with sensitive neuropathy should benefit from a gradual correction of their glycaemic imbalance in order to avoid the apparition of neuroarthropathy., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Charcot neuroarthropathy is a rare but often difficult to manage disease in the neuropathic patient. Early signs such as unremarkable edema, marginal trauma, or minor infection can activate a cascade of bony destruction and lead to gross prominence or deformity, with dire consequences. The exact molecular mechanism is poorly understood. Current theory states that an inflammatory reaction leads to the activation of osteoclasts mediated by specific cytokines. Our study sought to test the genetic expression of certain biomarkers in diabetic patients with and without Charcot neuroarthropathy compared with patients with and without diabetes or neuropathy. A total of 30 patients participated in the study, 17 (57%) males and 13 (43%) females. Peripheral blood samples were drawn, and gene expression was measured using real-time polymerase chain reaction. The expression levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin showed no significant increase in the Charcot neuroarthropathy group compared with the healthy control group. We determined that the levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin were not significantly increased in Charcot neuroarthropathy patients compared with healthy control patients. These results demonstrate a need for further investigation into alternative molecular pathways to determine the exact mechanism of the disease process., (Copyright © 2018 The American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.)

Objective: Due to the localized nature of Charcot foot, systemically altered levels of inflammation markers can be difficult to measure. The aim of this study was to investigate whether it is possible to detect an arteriovenous (A-V) flux in any locally produced inflammatory biomarkers from an acute Charcot foot by comparing local and systemic measurements., Methods: We included patients with acute diabetic Charcot foot. Blood was sampled from the vena saphena magna on the distal part of the crus bilaterally as well as from the arteria radialis. To minimize the A-V shunting effect, the feet were externally cooled with ice water prior to resampling., Results: Both before and after cooling, the A-V flux of interleukin-6 (IL-6) between the Charcot feet and the arterial level was significantly higher than the flux between the healthy feet and the arterial level (Δvalue before : 7.25 versus 0.41 pg/mL, resp., p = 0.008; Δvalue after : 10.04 versus 1.68 pg/mL, resp., p = 0.032). There were no differences in the fluxes for other markers of inflammation., Conclusion: We have found an increased A-V flux of IL-6 in the acute diabetic Charcot foot compared to the healthy foot in the same patients.

Background and Aims: Charcot foot is a rare but severe complication to diabetes and peripheral neuropathy. It is still unclear if an acute Charcot foot has long-term effects on the bone metabolism. To investigate this, we conducted a follow-up study to examine if a previously acute Charcot foot has any long-term effects on bone mineral density (BMD) or local or systemic bone metabolism., Methods: An 8.5-year follow-up case-control study of 44 individuals with diabetes mellitus, 24 of whom also had acute or chronic Charcot foot at the baseline visit in 2005-2007, who were followed up in 2015 with DXA scans and blood samples., Results: 21 of the 44 baseline participants participated in the follow-up. There were no difference in the change in total hip BMD from baseline to follow-up in either the Charcot or the control group (p = 0.402 and 0.517), and no increased risk of osteoporosis in the previous Charcot feet either. From baseline to follow-up, there was a significant difference in the change in levels of fsRANK-L in the Charcot group, but not in the control group (p = 0.002 and 0.232, respectively). At follow-up, there were no differences in fsRANK-L between the groups. The fsRANK-L/OPG ratio also significantly decreased from baseline to follow-up in the Charcot group (3.4 versus 0.5) (p = 0.009), but not in the control group (1.3 versus 1.1) (p = 0.302)., Conclusion: We found that diabetes patients with an acute Charcot foot have an elevated fsRANK-L/OPG ratio, and that the level decreased from baseline to follow-up to be comparable to the level in diabetes patients without previous or current Charcot foot. We found no permanent effect of an acute Charcot foot on hip or foot BMD., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Charcot arthropathy is one of the most serious complications of diabetic foot syndrome that leads to amputation of the affected limb. Since there is no cure for Charcot arthropathy, early diagnosis and implementation preventive care are the best available treatment. However, diagnosis is hindered by obscure clinical picture of the disease and lack of molecular markers for its early detection. Results of recent research suggest that OPG-RANKL-RANK axis regulating bone metabolism can be associated with Charcot arthropathy and that SNPs in OPG gene are associated with the disease. Here we report the results of comprehensive analysis of ten SNPs in OPG, RANKL and RANK genes in 260 subjects divided into diabetes, neuropathy and Charcot arthropathy groups. Besides genotype analysis we performed linkage disequilibrium and hierarchical clustering to obtain information about correlation between SNPs. Our results show that OPG 245T/G (rs3134069) and OPG 1217C/T (rs3102734) polymorphisms co-occur in patients with Charcot arthropathy (r2 = 0.99). Moreover, hierarchical clustering revealed a characteristic profile of all SNPs in Charcot arthropathy and neuropathy, which is distinct from control group. Our results suggest that analysis of multiple SNPs can be used as potential marker of Charcot arthropathy and provide insight into possible molecular mechanisms of its development.

Aims: Charcot neuroarthropathy (CN) is a disabling complication, culminating in bone destruction and involving joints and articular cartilage with high inflammatory environment. Its real pathogenesis is as yet unknown. In autoinflammatory diseases, such as rheumatoid arthritis, characterized by inflammation and joint involvement, autoantibodies against oxidative post-translationally modified (oxPTM) collagen type I (CI) and type II (CII) were detected. Therefore, the aim of our study was to assess the potential involvement of autoimmunity in charcot neuroarthropathy, investigating the presence of autoantibodies oxPTM-CI and oxPTM-CII, in participants with charcot neuroarthropathy., Methods: In this case-control study, we enrolled 124 participants with type 2 diabetes mellitus (47 with charcot neuroarthropathy, 37 with diabetic peripheral neuropathy without charcot neuroarthropathy, and 40 with uncomplicated diabetes), and 32 healthy controls. The CI and CII were modified with ribose and other oxidant species, and the modifications were evaluated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Binding of sera from the participants was analyzed with enzyme-linked immunosorbent assay., Results: Age, body mass index, waist and hip circumferences, and lipid profile were similar across the 4 groups, as well as glycated hemoglobin and duration of diabetes among people with diabetes. An increased binding to both native and all oxidation-modified forms of CII was found in participants with CN and diabetic neuropathy. Conversely, for CI, an aspecific increased reactivity was noted., Conclusions: Our results detected the presence of autoantibodies against oxidative post-translational modified collagen, particularly type 2 collagen, in participants with charcot neuroarthropathy and diabetic neuropathy, suggesting the possible involvement of autoimmunity. Further studies are required to understand the role of autoimmunity in the pathogenesis of charcot neuroarthropathy., (Copyright © 2016 John Wiley & Sons, Ltd.)

Introduction. The receptor activator of nuclear factor-kB (RANK), ligand (RANK-L) and osteoprotegerin (OPG) are implicated in the pathogenesis of acute Charcot neuroarthropathy (CN). Materials and Methods. This study aimed to investigate the expression of RANK-L and OPG in peripheral blood mononuclear cells (PBMC) from patients with acute CN. Results. We found that the expression of RANK-L was lower in patients with acute CN as compared with diabetic control subjects and healthy control participants; whereas OPG expression was not detected in patients and in both control groups. RANK-L expression at the onset of disease was inversely correlated with the index of polyunsaturation (PUI), a bone marrow MRS-derived measurable index that allows evaluation of disease activity in acute CN, and recovery time. Finally, the expression of RANK-L increased at the time of healing compared with the values found during the acute phase. Conclusions. In conclusion, our preliminary data provide a first step in applying analysis of RANK-L expression in peripheral blood cells to the diagnosis of acute CN. Based on our data we also suggest that analysis of RANK-L expression could be a complementary tool that can be employed to obtain quantitative parameters that may help clinicians to monitor disease activity in patients with acute CN., Competing Interests: The authors have declared that no competing interest exists.

Lubricin, encoded by the gene PRG4, is the principal lubricant in articulating joints. We immunized mice genetically deficient for lubricin (Prg4-/-) with purified human lubricin, and generated several mAbs. We determined each mAb's binding epitope, sensitivity, and specificity using biologic samples and recombinant lubricin sub-domains, and we also developed a competition ELISA assay to measure lubricin in synovial fluid and blood. We found the mAbs all recognized epitopes containing O-linked oligosaccharides conjugated to the peptide motif KEPAPTTT. By western blot, the mAbs detected lubricin in 1 μl of synovial fluid from several animal species, including human. The mAbs were specific for lubricin since they did not cross-react with other synovial fluid constituents from patients with camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP), who genetically lack this protein. The competition ELISA detected lubricin in blood samples from healthy individuals but not from patients with CACP, indicating blood can be used in a diagnostic test for patients suspected of having CACP. Lubricin epitopes in blood do not represent degradation fragments from synovial fluid. Therefore, although blood lubricin levels did not differentiate patients with inflammatory joint disease from healthy controls, epitope-specific anti-lubricin mAbs could be useful for monitoring disease activity in synovial fluid.

Aims: To assess markers of inflammation and bone turnover at presentation and at resolution of Charcot osteoarthropathy., Methods: We measured serum inflammatory and bone turnover markers in a cross-sectional study of 35 people with Charcot osteoarthropathy, together with 34 people with diabetes and 12 people without diabetes. In addition, a prospective study of the subjects with Charcot osteoarthropathy was conducted until clinical resolution., Results: At presentation, C-reactive protein (P = 0.007), tumour necrosis factor-α (P = 0.010) and interleukin-6 (P = 0.002), but not interleukin-1β, (P = 0.254) were significantly higher in people with Charcot osteoarthropathy than in people with and without diabetes. Serum C-terminal telopeptide (P = 0.004), bone alkaline phosphatase (P = 0.006) and osteoprotegerin (P < 0.001), but not tartrate-resistant acid phosphatase (P = 0.126) and soluble receptor activator of nuclear factor-κβ ligand (P = 0.915), were significantly higher in people with Charcot osteoarthropathy than in people with and without diabetes. At follow-up it was found that tumour necrosis factor-α (P = 0.012) and interleukin-6 (P = 0.003), but not C-reactive protein (P = 0.101), interleukin-1β (P = 0.457), C-terminal telopeptide (P = 0.743), bone alkaline phosphatase (P = 0.193), tartrate-resistant acid phosphatase (P = 0.856), osteoprotegerin (P = 0.372) or soluble receptor activator of nuclear factor-kβ ligand (P = 0.889), had significantly decreased between presentation and the 3 months of casting therapy time point, and all analytes remained unchanged from 3 months of casting therapy until resolution. In people with Charcot osteoarthropathy, there was a positive correlation between interleukin-6 and C-terminal telopeptide (P = 0.028) and tumour necrosis factor-α and C-terminal telopeptide (P = 0.013) only at presentation., Conclusions: At the onset of acute Charcot foot, serum concentrations of tumour necrosis factor-α and interleukin-6 were elevated; however, there was a significant reduction in these markers at resolution and these markers may be useful in the assessment of disease activity., (© 2014 The Authors. Diabetic Medicine © 2014 Diabetes UK.)

Objective: To evaluate whether bone marrow proton magnetic resonance spectroscopy (MRS) might provide a quantitative parameter able to assess disease activity in acute Charcot neuro-osteoarthropathy (CN)., Methods: Ten diabetic patients with stage 0 CN were prospectively evaluated at clinical onset and during treatment follow-up. The MRS lipid spectrum was analysed and a lipid polyunsaturation index (PUI) was calculated. Disease recovery was defined as the disappearance of bone marrow oedema as demonstrated on MRI short-tau-inversion-recovery (STIR) images. A 3-T MRI was used., Results: Inter- and intra-individual PUI measurements generated reproducible results with approximately 7 % and 6 % variation respectively. Baseline PUI values were significantly higher in patients with acute CN compared with controls. Also, a significant positive correlation was observed between baseline PUI values and serum levels of IL-6 and TNF-α. During follow-up a gradual decrease in PUI was observed. The percentage reduction of PUI values at 3 months' follow-up with respect to baseline values showed a negative correlation with recovery time., Conclusions: Bone marrow MRS may provide a measurable index that allows progressive evaluation of disease activity in acute CN. MRS may be a complementary tool that can be used to guide clinicians in the management of acute CN patients., Key Points: • Bone marrow MRS demonstrates lipid alterations in acute Charcot neuro-osteoarthropathy (CN). • Bone marrow MRS allows disease activity in acute CN to be evaluated. • MRS could become a new tool in the management of CN.

Aims: Recently, an association between two polymorphisms (1181G>C and 245T>G) of the osteoprotegerin (OPG) gene and diabetic Charcot neuroarthropathy was suggested on the basis of studies of a limited number of samples derived from subjects from one geographical region (Italy). The aim of this study was to assess the presence of various osteoprotegerin gene polymorphisms in patients with diabetes and Charcot neuroarthropathy compared with subjects with diabetic neuropathy but no Charcot foot and healthy controls from another geographical region (Poland)., Methods: DNA was isolated from 54 patients with Charcot neuroarthropathy, 35 subjects with diabetic neuropathy but no Charcot foot, and 95 healthy controls to evaluate OPG gene polymorphisms and their possible contribution to the development of Charcot neuroarthropathy., Results: Statistically significant differences between the group of subjects with neuropathy but no Charcot neuroarthropathy and the control group were found for 1217C>T, 950T>C and 245T>G polymorphisms, between the group of patients with Charcot neuroarthropathy and the control group for 1181G>C and 950T>C polymorphisms, and between the group of subjects with neuropathy but no Charcot neuroarthropathy and the group of patients with Charcot neuroarthropathy for 1217C>T and 245T>G polymorphisms., Conclusion: We suggest that genetic factors, particularly OPG gene polymorphisms, may play a role in the development of diabetic Charcot neuroarthropathy., (© 2011 The Authors. Diabetic Medicine © 2011 Diabetes UK.)

Background: This study was designed to compare the vitamin D levels in a cohort of nondiabetic patients to populations of diabetic patients with and without Charcot neuroarthropathy., Methods: A total of 41 participants (22 male, 19 female) with a mean +/- SD age of 59 +/- 9.43 years had serum 25-hydroxyvitamin D levels tested. Fifteen participants composed the nondiabetic group; 13, the group with diabetes but without Charcot neuroarthropathy; and 13, the group with both diabetes and Charcot neuroarthropathy., Results: The results of the study showed that the vitamin D levels in both diabetic populations were significantly lower (P < .05) than the nondiabetic population. There was no statistical difference between the group with diabetes but without Charcot foot disease and the group with both diabetes and Charcot neuroarthropathy., Conclusions: Based on the results of this study, given the importance of vitamin D in bone metabolism and the osseous consequences associated with diabetes, as well as other systems affected by low levels of vitamin D in the diabetic patient, it appears that vitamin D levels should be monitored in diabetic patients.

Vasomotion, the spontaneous rhythmic contraction exhibited by small arteries and arterioles is dysregulated in patients with diabetic neuropathy. We examined the relationship between Charcot arthropathy and vasomotion at the dorsum of the foot. We studied nine diabetic patients with clinically diagnosed neuropathy and Charcot arthropathy in 13 feet (n=13), twelve subjects with diabetic neuropathy and no Charcot deformity (n=12), and 11 healthy controls (n=11). Following neuropathy assessment, blood flow was measured by laser Doppler flowmetry with local skin warming. Fast Fourier transformation was performed to provide an index of vasomotion. Subjects with Charcot osteoarthropathy had more severe somatic neuropathy and higher circulating levels of serum calcium (9.8+/-0.1 versus 9.3+/-0.1 mg/dL). Raising local temperature increased skin blood flow and vasomotion in both control subjects and Charcot subjects, but not in diabetic patients with neuropathy alone (p < 0.05 for blood flow, p < 0.02 for vasomotion). Patterns of peripheral vasomotion and blood flow which are clearly disordered in diabetic neuropathy are intact in patients with a Charcot osteoarthropathy, despite a more severe sensory nerve impairment. These findings suggest that the loss of peripheral blood flow and vasomotion often seen in diabetic neuropathy may actually be protective against Charcot arthropathy by preventing bone resorption. It remains unclear then whether the Charcot arthropathy is a direct result of a failure to decrease blood flow to bone, or is the manifestation of some other pathology.

Four commercial test kits for parvovirus B19 IgM were evaluated by testing 491 sera assembled into 7 panels. The serum panels were designed to assess sensitivity and specificity of the commercial assays and to reflect the various clinical settings in which acute B19 infection forms part of the differential diagnosis. A mu-capture radioimmunoassay (MACRIA) was used as the reference test. With respect to MACRIA, the commercial B19 IgM assays showed an overall sensitivity of 70.1-84.1% and specificity of 92.2 to 97.4%. Assay performance varied in different clinical situations. In sera from adults with acute B19 arthropathy, all 4 assays were 100% sensitive, but in children with fifth disease, the sensitivity ranged from 44.1 to 88.6%. The sensitivity of all 4 assays was also low when testing samples collected more than 6 weeks after onset of symptoms and in women with B19-associated embryopathy. Specificity was greater than 97% in healthy blood donors, but varied from 70.9 to 83.3% in patients acutely infected with other viruses, including rubella. Although the IgM test kits here evaluated may be usefully introduced for B19 diagnosis in certain settings, knowledge of their limitations will be important when results have been interpreted.