Determination of pyrophosphate in renal calculi and urine by means of an enzymatic method

Ratiometric fluorescent sensing of pyrophosphate with sp³-functionalized single-walled carbon nanotubes

Inorganic pyrophosphate is a key molecule in many biological processes from DNA synthesis to cell metabolism. Here we introduce sp3-functionalized (6,5) single-walled carbon nanotubes (SWNTs) with red-shifted defect emission as near-infrared luminescent probes for the optical detection and quantification of inorganic pyrophosphate. The sensing scheme is based on the immobilization of Cu2+ ions on the SWNT surface promoted by coordination to covalently attached aryl alkyne groups and a triazole complex. The presence of Cu2+ ions on the SWNT surface causes fluorescence quenching via photoinduced electron transfer, which is reversed by copper-complexing analytes such as pyrophosphate. The differences in the fluorescence response of sp3-defect to pristine nanotube emission enables reproducible ratiometric measurements in a wide concentration window. Biocompatible, phospholipid-polyethylene glycol-coated SWNTs with such sp3 defects are employed for the detection of pyrophosphate in cell lysate and for monitoring the progress of DNA synthesis in a polymerase chain reaction. This robust ratiometric and near-infrared luminescent probe for pyrophosphate may serve as a starting point for the rational design of nanotube-based biosensors.

FeMoO4 nanospheres-based nanozymatic colorimetry for rapid and sensitive pyrophosphate detection

Assays of pyrophosphate ion (PPi) are of remarkable biochemical significance due to their vital roles in the bioenergetic and metabolic processes or as disease indicators. Colorimetry is popular in the field of biosensing and detection because of its simplicity, speed and cost-effectiveness, but there is a lack of a suitable colorimetric probe. Herein, a novel colorimetric sensing platform has been established for the detection of pyrophosphate based on the FeMoO₄-H₂O₂-3,3',5,5'-tetra-methylbenzidine (TMB) system. Compared with most previously reported iron-based nanozymes, the as-obtained FeMoO₄ nanospheres with a rough surface possessed a much superior peroxidase-like catalytic activity (V_max = 28.47 × 10^-8 M s^-1) and substrate affinity (K_m = 0.174 mM) toward H₂O₂ catalysis. Due to the Fe(II) and PPi reaction, the presence of PPi could specifically restore blue oxidized TMB to colorless TMB, which led to a decrease in UV absorption at 652 nm. The absorbance change is proportional to the PPi concentration, with a linear detection range (from 0.5 to 25 μM) and a low detection limit of 0.3 μM (S/N = 3). Accordingly, its excellent selectivity and high sensitivity made it a potential colorimetric sensor for PPi analysis in actual water samples.

A colorimetric indicator-displacement assay based on stable Cu2+ selective carbon dots for fluorescence turn-on detection of pyrophosphate anions in urine

Determination of PPi levels in urine represents a measurable factor for diagnostic, treatment, and monitoring of urolithiasis. Owing to the quenching ability of Cu²⁺ on fluorescent carbon dots (CDs) and strong binding affinity between Cu²⁺ and PPi, we develop a new off-on assay for PPi detection using newly BPHA CDs (BPHA: N,N-bis(pyridin-2-ylmethyl)hexan-1-amine). The fluorescence intensity of BPHA CDs was significantly quenched by Cu²⁺ ("off") through forming BPHA CDs/Cu²⁺ complexes and the fluorescence intensity of BPHA CDs /Cu²⁺ system was completely resumed by PPi ("on") owing to the release of free Cu²⁺. The fluorescence turn-off/on approach showed a highly selective response to PPi over the large family of other anions. The detection limits were 0.094 μM for Cu²⁺ and 0.025 μM for PPi, respectively. A wide linear range for PPi was up to 4400 μM. The indicator displacement assay (IDAs) using pyrocatechol violet (PV) as a colorimetric indicator was carried out to detect PPi with the naked eyes. The "off-on" fluorescent sensor based on BPHA CDs shows many merits, including convenient operation, cost-saving, high sensitivity, selectivity, stability and wide detecting range, which is applied to PPi detection in human urine sample.

Silk Fibroin-Confined Star-Shaped Decahedral Silver Nanoparticles as Fluorescent Probe for Detection of Cu2+ and Pyrophosphate

A green, one-step method for the fabrication of silk fibroin (SF) protected silver decahedral nanoparticles (SF@AgNPs) has been developed. High-resolution transmission electron microscopy characterization demonstrated that the silver decahedral nanoparticles can provide more binding sites with (111) facets. Moreover, a facile strategy based on Cu²⁺ mediated SF@AgNPs was reported as an on-off-on fluorescent system for the detection of Cu²⁺, and the SF@AgNPs can be also used for the determination of pyrophosphate ion (P₂O₇^4-, PPi). The fluorescence of SF@AgNPs was quenched by Cu²⁺ as a complex formed between SF and Cu²⁺ and was restored when PPi was introduced into the system due to the higher binding affinity between PPi and Cu²⁺. Herein, a novel SF@AgNPs-Cu²⁺ fluorescent probe for Cu²⁺ and PPi detection is presented. The proposed assay shows a linear relationship at a Cu²⁺ concentration range from 1 to 6 μM with a detection limit of 33.3 nM. This simple, reliable, selective, and environmentally friendly fluorescent probe also has a wide concentration range from 100 to 700 μM with a detection limit of 6.7 μM for PPi. The 16 types of anions lead to negligible changes in the SF@AgNPs-Cu²⁺ complexes, while restoring the fluorescence intensity of the complexes when added with PPi. Additionally, it is demonstrated that the SF@AgNPs-based fluorescent assay works in real biological samples. It suggests that this proposed method has the potential for application in the clinical detection of Cu²⁺ and PPi.

Silica-polydopamine hybrids as light-induced oxidase mimics for colorimetric detection of pyrophosphate

In this study, silica-polydopamine hybrids (SPDA) were fabricated by a facile and one-step heating method using dopamine and (3-aminopropyl)triethoxysilane (APTES) as the reaction reagents. It was firstly found that light illuminated-SPDA could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue ox-TMB. The coloration process was quenched very efficiently via the addition of Cu2+. The presence of pyrophosphate ion (PPi) in the solution of light-illuminated SPDA-Cu2+-TMB induced the recovery of the coloration process. The recovery occurred because PPi coordinated with Cu2+, effectively sequestering the ion from SPDA. A calibration curve was developed that is related to the extent of absorption recovery to [PPi], making the SPDA-Cu2+-TMB system a sensitive and selective turn-on sensor for PPi detection. The limit-of-detection (LOD) for PPi was 0.06 μmol L-1 (S/N = 3) with a linear dynamic range of 0.1-30 μmol L-1 and the calibration curve of linear equation is given as: y = 0.00146x + 0.05096 (r = 0.9974). The proposed method has been successfully applied to the detection of PPi in human serum with satisfactory recovery. The simplicity, low cost, high sensitivity, good reproducibility and excellent selectivity of the PPi detection platform based on the light-induced oxidase mimicking property of SPDA makes it promising for further applications of SPDA in chemo/biosensing.

A Conjugated Polymer Fluorescent Sensor for Continuous Identification of Copper(II) and Pyrophosphate in Blood Serum and Synovial Fluid

A novel "on-off-on" super-sensitive conjugated polymer fluorescence sensor (PPE-DPA) was developed and it was applied to realize the continuous recognition of Cu²⁺ and pyrophosphate (PPi). The fluorescence intensity decreased linearly with the change of Cu²⁺ from 0.05 to 5.0 μmol L^-1 and the limit of detection was 24 nmol L^-1. The fluorescence intensity was linearly enhanced with the increase of PPi from 0.5 to 12.0 μmol L^-1 and the limit of detection was 230 nmol L^-1. In addition, this method was applied to detect PPi in the blood serum and synovial fluid of patients with arthritis and satisfactory results were obtained. Thus, the PPE-DPA is not only an effective tool for detecting Cu²⁺ and PPi in samples, but also presents a potential way to diagnose arthritis.

One-step synthesis of a dual-emitting carbon dot-based ratiometric fluorescent probe for the visual assay of Pb2+ and PPi and development of a paper sensor

Herein, an easy and effective ratiometric fluorescent nanoprobe for the selective detection of Pb²⁺ and pyrophosphate (PPi) was developed based on label-free carbon dots (CDs).

Pyrophosphate Recognition and Sensing in Water Using Bis[zinc(II)dipicolylamino]-Functionalized Peptides

Phosphate oxoanions and phosphorylated biomolecules (such as nucleotides, lipids, and proteins) play key roles in a wide range of biological processes. The ability to selectively detect these ions in the presence of each other has numerous applications in biochemistry and biomedicine. However, receptors and sensors that can discriminate between polyphosphate species with high selectivity and in biologically relevant conditions are rare. In this Account, we show how peptides (both cyclic and linear) can be used to position two zinc(II)dipicolylamine [Zn(II)DPA] binding sites in an appropriate arrangement to provide selective binding of pyrophosphate (PPi) in the presence of other polyphosphate species, including ATP, and in complex media such as cell growth buffer. The use of peptide scaffolds to position the Zn(II)DPA anion binding sites allowed the synthesis of small receptor libraries in which the arrangement of the two binding sites could be subtly altered to evaluate the factors affecting both binding selectivity and affinity for PPi. We altered a number of structural elements including peptide length, cyclic peptide ring size, amino acid composition, the positioning of the binding sites with respect to one another, and the relative stereochemistry of the peptides. Backbone modified cyclic peptides based on the Lissoclinum class of natural products were initially employed to provide an added degree of preorganization to the receptors, although it was subsequently found that short, flexible bis[Zn(II)DPA]-functionalized linear peptides are also effective scaffolds for selective pyrophosphate recognition. The peptidic receptors were successfully employed for the detection of PPi in aqueous media by indicator displacement assays using both colorimetric and fluorescent indicators, with the best compounds able to bind to PPi selectively in both cell growth media and artificial urine and also allow the accurate determination of PPi concentrations in physiologically relevant ranges (micromolar concentrations) in these complex media. Improved pyrophosphate selectivity was observed upon increasing the complexity of the media from HEPES buffer to cell growth media (Krebs saline). Pyrophosphate sensors in which a fluorescent indicator was covalently attached to either a linear or cyclic peptide scaffold through a flexible linker were then constructed. When the Zn(II)DPA binding sites and the indicator were suitably placed with respect to one another on the peptide scaffold, these 'intramolecular indicator displacement assays' showed improved selectivity for PPi over other polyphosphate anions, such as ATP, when compared to the intermolecular indicator displacement assays. This observation provides the basis for the design and application of future PPi sensors in biochemistry and biomedicine.

Intraperitoneal pyrophosphate treatment reduces renal calcifications in Npt2a null mice

Mutations in the proximal tubular sodium-dependent phosphate co-transporters NPT2a and NPT2c have been reported in patients with renal stone disease and nephrocalcinosis, however the relative contribution of genotype, dietary calcium and phosphate, and modifiers of mineralization such as pyrophosphate (PPi) to the formation of renal mineral deposits is unclear. In the present study, we used Npt2a^-/- mice to model the renal calcifications observed in these disorders. We observed elevated urinary excretion of PPi in Npt2a^-/- mice when compared to WT mice. Presence of two hypomorphic Extracellular nucleotide pyrophosphatase phosphodiesterase 1 (Enpp1^asj/asj) alleles decreased urine PPi and worsened renal calcifications in Npt2a^-/- mice. These studies suggest that PPi is a thus far unrecognized factor protecting Npt2a^-/- mice from the development of renal mineral deposits. Consistent with this conclusion, we next showed that renal calcifications in these mice can be reduced by intraperitoneal administration of sodium pyrophosphate. If confirmed in humans, urine PPi could therefore be of interest for developing new strategies to prevent the nephrocalcinosis and nephrolithiasis seen in phosphaturic disorders.

Systemic endothelial function measured by flow-mediated dilation is impaired in patients with urolithiasis

Some in vitro and animal studies have shown endothelial dysfunction in hyperoxaluria models indicating its role in pathogenesis of urolithiasis and relation to CVD. The aim of this study was to investigate endothelial function in patients with urolithiasis in relation to urinary stone risk factors and metabolic parameters. A total of 120 subjects without any known CVD (60 with urolithiasis and 60 healthy subjects) were included into study. Fasting blood and 24-h urine samples were collected to study metabolic parameters (glucose and lipids) and urine stone risk factors (oxalate, citrate, uric acid, and calcium, pH). Endothelial function was assessed as flow-mediated dilation (FMD) at the brachial artery. Age, sex, and body mass index were similar in patients and controls. Of urine stone risk factors, oxalate and citrate were higher in patients than controls. Fasting blood glucose, total LDL cholesterol, and triglyceride were higher, and HDL cholesterol was lower in patients than controls. Although within normal limits systolic blood pressure was higher in patient group, patients with urolithiasis had a lower %FMD than controls. Percent FMD was negatively correlated with urinary oxalate/creatinine ratio (p = 0.019, r = -0.315), calcium/creatinine ratio (p = 0.0001, r = -0.505) age (p < 0.001, r = -0.694), BMI (p < 0.001, r = -0.838), total cholesterol (p < 0.001, r = -0.559), and triglyceride (p < 0.001, r = -0.529). Urine oxalate/creatinine ratio was positively correlated with age (p = 0.01, r = 0.327) and calcium/creatinine ratio with BMI (p = 0.001, r = 0.410). This is the first study demonstrating endothelial dysfunction in human subjects with urolithiasis. This indicates a possible predictive role of urolithiasis in future development of cardiovascular diseases.

One-pot synthesis of highly greenish-yellow fluorescent nitrogen-doped graphene quantum dots for pyrophosphate sensing via competitive coordination with Eu(3+) ions

Highly fluorescent nitrogen-doped graphene quantum dots (N-GQDs) with greenish-yellow emission and quantum yield of 13.2% have been synthesized via a one-pot hydrothermal method. The obtained N-GQDs displayed excellent optical properties, high photostability and resistance to strong ion strength. Based on the higher affinity of pyrophosphate (PPi) than carboxyl and amido groups on the surface of the N-GQDs to Eu(3+), a Eu(3+)-modulated N-GQD off-on fluorescent probe for PPi detection was constructed with a detection limit of 0.074 μM. The detection process was simple in design, easy to operate, and showed a highly selective response to PPi in the presence of co-existing anions. This work widens the applications of N-GQDs with versatile functionality and reactivity in clinical diagnostics and as biosensors.

High-throughput and rapid fluorescent visualization sensor of urinary citrate by CdTe quantum dots

In this paper, we have presented a novel CdTe quantum dots (QDs) based fluorescent sensor for visual and turn-on sensing of citrate in human urine samples. The europium ion (Eu(3+)) can lead to the fluorescence quenching of thioglycollic acid (TGA) modified CdTe QDs due to photoinduced electron transfer accompanied by the change of emission color from yellow to orange. Next, addition of citrate breaks the preformed assembly because citrate can replace the CdTe QDs, based on the fact that the Eu(3+) ion displays higher affinity with citrate than the CdTe QDs. Thus the photoinduced electron transfer is switched off, and the fluorescence emission of CdTe QDs is rapidly (within 5min) recovered, simultaneously, the orange emission color restores to yellow. Such proposed strategy may conveniently discriminate the patient of renal stone from normal person by naked eyes. In addition to visualization detection, the fluorescence responses can be used for well quantifying citrate in the range of 0.67-133μM. So, the present, simple, low-cost and visualized citrate fluorescence sensor has great potential in the applications for earlier screening in clinical detection.

Selective sensing of pyrophosphate in physiological media using zinc(ii)dipicolylamino-functionalised peptides

Linear zinc(ii)dipicolylamino-functionalised peptides show high affinity and selectivity for pyrophosphate in physiological media.

Multisystemic functions of alkaline phosphatases

Human and mouse alkaline phosphatases (AP) are encoded by a multigene family expressed ubiquitously in multiple tissues. Gene knockout (KO) findings have helped define some of the precise exocytic functions of individual isozymes in bone, teeth, the central nervous system, and in the gut. For instance, deficiency in tissue-nonspecific alkaline phosphatase (TNAP) in mice (Alpl (-/-) mice) and humans leads to hypophosphatasia (HPP), an inborn error of metabolism characterized by epileptic seizures in the most severe cases, caused by abnormal metabolism of pyridoxal-5'-phosphate (the predominant form of vitamin B6) and by hypomineralization of the skeleton and teeth featuring rickets and early loss of teeth in children or osteomalacia and dental problems in adults caused by accumulation of inorganic pyrophosphate (PPi). Enzyme replacement therapy with mineral-targeting TNAP prevented all the manifestations of HPP in mice, and clinical trials with this protein therapeutic are showing promising results in rescuing life-threatening HPP in infants. Conversely, TNAP induction in the vasculature during generalized arterial calcification of infancy (GACI), type II diabetes, obesity, and aging can cause medial vascular calcification. TNAP inhibitors, discussed extensively in this book, are in development to prevent pathological arterial calcification. The brush border enzyme intestinal alkaline phosphatase (IAP) plays an important role in fatty acid (FA) absorption, in protecting gut barrier function, and in determining the composition of the gut microbiota via its ability to dephosphorylate lipopolysaccharide (LPS). Knockout mice (Akp3 (-/-)) deficient in duodenal-specific IAP (dIAP) become obese, and develop hyperlipidemia and hepatic steatosis when fed a high-fat diet (HFD). These changes are accompanied by upregulation in the jejunal-ileal expression of the Akp6 IAP isozyme (global IAP, or gIAP) and concomitant upregulation of FAT/CD36, a phosphorylated fatty acid translocase thought to play a role in facilitating the transport of long-chain fatty acids into cells. gIAP, but not dIAP, is able to modulate the phosphorylation status of FAT/CD36. dIAP, even though it is expressed in the duodenum, is shed into the gut lumen and is active in LPS dephosphorylation throughout the gut lumen and in the feces. Akp3 (-/-) mice display gut dysbiosis and are more prone to dextran sodium sulfate-induced colitis than wild-type mice. Of relevance, oral administration of recombinant calf IAP prevents the dysbiosis and protects the gut from chronic colitis. Analogous to the role of IAP in the gut, TNAP expression in the liver may have a proactive role from bacterial endotoxin insult. Finally, more recent studies suggest that neuronal death in Alzheimer's disease may also be associated with TNAP function on certain brain-specific phosphoproteins. This review recounts the established roles of TNAP and IAP and briefly discusses new areas of investigation related to multisystemic functions of these isozymes.

A molecular logic gate for the highly selective recognition of pyrophosphate with a hypocrellin A-Zn(II) complex

Pyrophosphate (PPi) participates in many biological and chemical processes such as energy transduction so that investigations on its role and detection have become very significant. In this contribution, we have developed a molecular logic gate for the recognition of PPi with a fluorescent hypocrellin A-zinc(II) complex (HA-Zn(2+)), and the outputs of which correspond to the fluorescence emission ratio at 604 nm and wavelength shift relative to 629 nm. The emission at 604 nm is the intrinsic fluorescence of HA, which can be effectively quenched by Zn(2+) with a new emission at 629 nm owing to the formation of the HA-Zn(2+) complex. It was found, however, that the new emission at 629 nm is highly selectively quenched with the addition of PPi, recovering the emission at 604 nm, and the recovery ratio is linearly correlated with PPi in the range of 1.8 × 10(-5) mol L(-1) to 2.4 × 10(-4) mol L(-1). ATP, UTP, CTP, GTP, GDP and GMP cannot demonstrate the same spectral actions as PPi. Since the inputs of PPi and the phosphate anions obtain different logical outputs, the designed logic gates have good selectivity and can distinguish PPi from the other anions.

Expression and Localisation of the Pyrophosphate Transporter, ANK, in Murine Kidney Cells

BACKGROUND/AIMS

Mutation of the pyrophosphate transporter, ANK, results in progressive arthritis in mice. ANK is expressed in non-skeletal tissues including kidney. The aim was therefore to investigate ANK location at the cellular and subcellular level in renal cells.

METHODS

RT-PCR identified a murine cell-line, mIMCD3, expressing ANK. The intra-renal distribution of ANK was determined by immunohistochemistry and the subcellular distribution in mIMCD3 cells by transfection of an ANK-NT-GFP fusion protein. Furthermore, an inactivating mutation of murine ank, Glu440X, and a gain of function mutation, Met48Thr, were tested to determine whether membrane traffic contributed to a transport defect.

RESULTS

ANK is expressed in cells of the cortical collecting duct, as assessed by colocalisation with aquaporin 2 and at the lateral and apical plasma membranes of mIMCD-3 epithelial cells, as assessed by colocalisation with wheat germ agglutinin lectin (WGA). ANK-NT-GFP was also present in endoplasmic reticulum, Golgi, acidic endosomes and mitochondria. mIMCD3 expression of Glu440X ANK-NT-GFP shows evidence of Golgi retention whereas Met48Thr ANK-NT-GFP is unaltered at the plasma membrane compared to wild type.

CONCLUSION

The intra-renal and subcellular localisation of ANK is consistent with pyrophosphate export from collecting duct cells and supports a role for ANK in limiting intra-renal calcium-crystal formation.

Renal calcium stones: insights from the control of bone mineralization

Extracellular pyrophosphate (PPi) plays a central role in the control of normal bone mineralization since it antagonizes inorganic phosphate in the promotion of hydroxyapatite deposition. Studies using knock-out mice have established the functional importance of PPi generation via nucleotide pyrophosphatase phosphodiesterases (NPP) and of PPi transmembrane transport by the progressive ankylosis (ANK) protein. Tissue non-specific alkaline phosphatase activity counteracts this by hydrolysis of PPi to inorganic phosphate. The molecular nature and transport function of ANK are reviewed. A close parallel is drawn between the controlled mineralization of bone and the prevention of abnormal calcium crystal deposition within the kidney, especially when concentrated urine is produced. Pyrophosphate is present in urine, and ANK is expressed in the cortical collecting duct where PPi transport to both the tubular lumen and the renal interstitium may occur. Pyrophosphate may also be generated here by nucleoside triphosphate diphosphohydrolases (NTPD2 and 3) together with NPP1. Alkaline phosphatase activity is restricted to the proximal nephron, remote from these sites of PPi generation, transport and function. The physiological importance of PPi generation and transport in preventing idiopathic calcium renal stone disease and nephrocalcinosis now needs to be established.

Inhibitors of calcification in blood and urine

In bone and teeth formation, coordinated calcification is a highly desirable biological process. However, heterotopic calcification at unwanted tissue sites leads to dysfunction, disease and, potentially, to death and therefore requires prevention and treatment. With the recent discovery of calcification inhibitors we now know that biological calcification is not passive but a complex, active and highly regulated process. Calcification at vascular sites is the most threatening localization and manifests as part of atherosclerosis or arteriosclerosis. Atherosclerosis is often accompanied by intimal plaque calcification, whereas arteriosclerosis is characterized by calcification of the media. The severity of calcification of cerebral or coronary atherosclerotic plaques is associated with an increased incidence of events such as stroke or myocardial infarction. Medial calcification is the major cause of arterial stiffness, which contributes to left ventricular dysfunction and heart failure. Patients with chronic kidney disease are at especially increased risk for both intimal and medial calcification. In this context, it is currently thought that calcium-regulatory factors including fetuin-A, matrix Gla protein, osteoprotegerin, and pyrophosphates act in a local or systemic manner to prevent calcifications of the vasculature, and that dys-regulations of such calcification inhibitors may contribute to progressive calcifications. Nephrolithiasis represents another process of unwanted calcification responsible for significant morbidity. More than 80% of renal stones contain calcium. Urinary factors inhibiting calcification are citrate, glycosaminoglycans, Tamm-Horsfall protein, and osteopontin. This review summarizes current experimental and clinical data underlining the biological importance of these calcification inhibitors.

Synovial Chondromatosis of the Temporomandibular Joint: Report and Analysis of Eleven Cases

PURPOSE

Synovial chondromatosis (SC) is a benign monoarticular condition that is uncommon in the temporomandibular joint (TMJ). The purpose of this article is to present 11 additional cases of SC of the TMJ and discuss newer modes of imaging, diagnostic approaches, treatment options, and follow-up data.

METHODS

Medical records of 11 patients with SC treated within our department from 1991 to the present were reviewed. Demographic data, etiology, clinical presentation, diagnostic evaluation, treatment, and follow-up information were collected. Previously reported cases (both TMJ and others) from 1988 to present were identified for comparison and the literature reviewed.

RESULTS

There were 8 females and 3 males with an average age of 54 years. Pain and preauricular swelling were the most common presenting clinical complaints. Etiologic factors (parafunction, inflammatory joint disease) were found in 7 of 11 cases. Plain radiographs showed joint calcifications in only 2 of 11 cases. Computed tomography identified calcifications in 3 of 6. Magnetic resonance imaging clearly demonstrated the mass and its extension in 10 of 10 cases. Fine needle aspiration was diagnostic in 4 of 9. All patients were treated with an open arthrotomy. Meniscectomy was required in 7 of 11. Average follow-up was 5.2 years with no recurrences reported.

CONCLUSION

The current case series of SC shows a female predilection with age and presenting complaints similar to those previously reported. A traumatic etiology was not identified, although a weak association is reported in the literature. The superiority of magnetic resonance imaging for both diagnosis and evaluation of extension of disease is shown. In a subset of cases, fine needle aspiration is useful for confirming the clinicoradiographic impression. Complete removal of involved tissue is associated with an excellent prognosis.