Update in calcium deposition diseases

Amorphous 1-D nanowires of calcium phosphate/pyrophosphate: A demonstration of oriented self-growth of amorphous minerals

Amorphous inorganic solids are traditionally isotropic, thus, it is believed that they only grow in a non-preferential way without the assistance of regulators, leading to the morphologies of nanospheres or irregular aggregates of nanoparticles. However, in the presence of (ortho)phosphate (Pi) and pyrophosphate ions (PPi) which have synergistic roles in biomineralization, the highly elongated amorphous nanowires (denoted ACPPNs) form in a regulator-free aqueous solution (without templates, additives, organics, etc). Based on thorough characterization and tracking of the formation process (e.g., Cryo-TEM, spherical aberration correction high resolution TEM, solid state NMR, high energy resolution monochromated STEM-EELS), the microstructure and its preferential growth behavior are elucidated. In ACPPNs, amorphous calcium orthophosphate and amorphous calcium pyrophosphate are distributed at separated but close sites. The ACPPNs grow via either the preferential attachment of ∼2 nm nanoclusters in a 1-dimension way, or the transformation of bigger nanoparticles, indicating an inherent driving force-governed process. We propose that the anisotropy of ACPPNs microstructure, which is corroborated experimentally, causes their oriented growth. This study proves that, unlike the conventional view, amorphous minerals can form via oriented growth without external regulation, demonstrating a novel insight into the structures and growth behaviors of amorphous minerals.

Sonographic assessment of calcium pyrophosphate deposition disease at wrist. A focus on the dorsal scapho-lunate ligament

OBJECTIVES

To investigate the diagnostic accuracy of ultrasound and conventional radiography in the evaluation of calcium pyrophosphate crystal deposits at wrist level.

METHODS

Consecutive patients with a "definite" diagnosis of calcium pyrophosphate deposition disease and disease-controls were prospectively included in this cross-sectional single-centre study. Scapho-lunate ligament, triangular fibrocartilage complex, and volar recess of the radio-lunate joint were explored using ultrasound, conventional radiography and computed tomography.

RESULTS

Sixty one patients and 39 disease controls were enrolled. Two-hundred wrists were evaluated using both conventional radiography and ultrasound and 26 using computed tomography. Ultrasound findings indicative of crystal deposits were found in at least one wrist in 95.1% of patients and in 15.4% of controls (P<0.001). Scapho-lunate ligament calcifications were reported in 83.6% of patients and in 5.1% of controls (P<0.001). On conventional radiography, calcifications were found in at least one wrist in 72.1% of patients and in 0% of controls (P<0.001). Using the Ryan-McCarty criteria as a gold standard, sensitivity, specificity and diagnostic accuracy were 0.72 (0.59-0.83), 1.0 (0.91-1.0) and 0.83 (0.74-0.90) for conventional radiography and 0.95 (0.86-0.99), 0.85 (0.69-0.94) and 0.91 (0.84-0.96) for ultrasound. The agreement between ultrasound and computed tomography was substantial when assessing triangular fibrocartilage complex (kappa=0.70; 0.43-0.97) and scapho-lunate ligament (kappa=0.69; 0.41-0.97), and moderate for radio-lunate joint (kappa=0.46; 0.12-0.80).

CONCLUSIONS

This study supports the diagnostic accuracy of ultrasound in evaluating wrist involvement in calcium pyrophosphate deposition disease. The inclusion of the scapho-lunate ligament in a disease-oriented scanning protocol could improve the diagnostic performance of ultrasound.

Ultrashort Time to Echo Magnetic Resonance Evaluation of Calcium Pyrophosphate Crystal Deposition in Human Menisci

OBJECTIVES

In human menisci, we aimed to investigate whether calcium pyrophosphate crystal deposition (CPPD) affects biomechanical and quantitative MR properties, and their zonal distribution.

MATERIALS AND METHODS

From 9 cadaveric knees, sectioned triangular meniscus pieces were harvested. Samples were classified into "normal" or "CPPD" groups based upon visual inspection. Micro computed tomography scan verified CPPD. Using magnetic resonance imaging, ultrashort echo time (UTE) T2* and spin echo (SE) T2, quantitative values in 3 zones (red, red-white, and white) were determined. Using biomechanical test, indentation forces in the same zones were determined. Effects of CPPD and meniscal zone on indentation force and quantitative MR values were compared.

RESULTS

On UTE MRI scans, CPPD-affected menisci exhibited punctate dark regions, found mostly (92%) in avascular white and red-white zones. Indentation forces were significantly higher for CPPD samples in the red-white (all P < 0.02) and white (all P < 0.004) zones but not in the vascular red zone (all P > 0.2). Similarly, UTE T2* red zone values were similar between both groups (~6.6 milliseconds, P = 0.8), whereas in the red-white and white zones, CPPD samples had significantly lower values (~5.1 milliseconds, P = 0.005 to 0.007). In contrast, SE T2 values showed no difference with CPPD (P = 0.12 to 0.16). UTE T2*, but not SE T2, correlated significantly with indentation force (R = -0.29, P = 0.009).

CONCLUSIONS

Dark CPP deposits were detectable on UTE images featuring high signal intensity from surrounding meniscal tissue. Preliminary results indicate that CPP deposits were almost exclusively found in the avascular zones. Compared with normal, CPPD menisci featured higher indentation stiffness and lower UTE T2* values in the affected zones.

Current strategy in the treatment of calcium pyrophosphate crystal deposition disease

The paper considers currently available drugs used to treat calcium pyrophosphate crystal deposition disease. It discusses the advantages and disadvantages of the most widely used drugs, such as  nonsteroidal anti-inflammatory drugs, colchicine, glucocorticoids, traditional immunosuppressants, as well as prospects for the use of biologic agents.

Microcalcification of lumbar spine intervertebral discs and facet joints is associated with cartilage degeneration, but differs in prevalence and its relation to age

Cartilage calcification (CC) is associated with degeneration in non-vertebral joints, but little is known about CC and lumbar vertebral joints. The goal of this study was to analyze the prevalence of CC in lumbar facet joints (FJ) and intervertebral discs (IVD) and its relation to cartilage degeneration and age in a non-selected cohort of the general population. The segment L4/5 of 85 consecutive donors (mean age 61.9 years) was analyzed by high-resolution imaging digital-contact radiography (DCR). Quantification was achieved by measuring CC in % of total cartilage area. Histological degeneration of FJs and IVDs was determined by OARSI and Boos scores. Prevalence of CC was 36.5% for FJ (95%CI (0.26, 0.48)) and 100% for IVD (95%CI (0.96, 1.00)). The amount of IVD CC (3.36% SD ± 7.14) was 16.3 times higher (p < 0.001) than that of the FJ (0.23% SD ± 0.53) and independent of each other (p = 0.07). The amount of FJ CC correlated significantly with FJ and IVD degeneration (FJ r = 0.44, p = 0.01, IVD r = 0.49, p = 0.006) while the amount of IVD CC correlated only with IVD degeneration (r = 0.54, p < 0.001). Age correlated with IVD CC (r_s  = 0.35, p < 0.001), but not FJ CC (r_s  = 0.04, p = 0.85). We conclude that IVD fibrocartilage is particularly prone to calcification. A causal relationship between lumbar CC and degeneration is possible, but the clear differences in IVD fibrocartilage CC and FJ synovial joint CC in regard to prevalence and in relation to age point to a differential role of CC in single compartments of the respective motion segment in lumbar spine degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2692-2699, 2017.

Current advances in therapies for calcium pyrophosphate crystal arthritis

PURPOSE OF REVIEW

Calcium pyrophosphate (CPP) crystal disease is a common rheumatologic disorder that has received limited attention from the scientific community. This review is aimed at summarizing current evidence for managing CPP disease (CPPD), focusing on recently reported advances.

RECENT FINDINGS

New data from case series indicate that interleukin-1β inhibitors can help patients with refractory forms of CPPD. Methotrexate, formerly a promising agent, failed to demonstrate benefits in a recent trial, but still merits consideration for some patients. No significant advances on crystal dissolution have been achieved to date. Proper characterization of the CPP crystal disease picture is needed, ruling out the possible coexistence of another persistent arthritis unrelated to the CPP deposition.

SUMMARY

Advances on CPP crystal dissolution and establishing definitions of the clinical spectrum of CPPD remain the main challenges for CPP crystal disease management.

Articular cartilage calcification of the hip and knee is highly prevalent, independent of age but associated with histological osteoarthritis: evidence for a systemic disorder

OBJECTIVES

Based on the concept of a systemic predisposition for articular cartilage calcification (CC), the aim of this study was to determine the prevalence and amount of bilateral CC of hip and knee joints in an unselected sample cohort by high-resolution digital contact radiography (DCR) and to analyze the association of CC with histological OA.

METHODS

Both hip and knee joints of 87 donors (48 m and 39 f; mean age 62) were analyzed by DCR in this post-mortem study of an unselected cohort of donors. Histological OA (OARSI) of the main load bearing area of femoral heads and medial femoral condyles was determined.

RESULTS

The prevalence of CC of the femoral head was 96.6%, of the knee 94.3%. Bilateral calcification was detected in 79.3% of hips and 86.2% of knees. Concomitant CC of all four joints was detected in 69.0% of donors. There was no difference between the amount of CC of hips and knees (P = 0.47). The amount of CC of any given hip or knee correlated with that of the contralateral hip (r_s = 0.54, P < 0.001) or knee (r_s = 0.50, P < 0.001). There was a correlation between the amount of CC and histological OA (hips r_s = 0.48, P < 0.001, knees r_s = 0.30, P = 0.004), but not between CC and age (hips r_s = -0.09, P = 0.42; knees r_s = 0.10, P = 0.34).

CONCLUSIONS

These data support the concept that articular CC occurs as the result of a systemic disorder. CC appears to be an early element of hip and knee OA pathogenesis independent of age.

Hyaline cartilage calcification of the first metatarsophalangeal joint is associated with osteoarthritis but independent of age and BMI

Background

Hyaline cartilage calcification (CC) is associated with osteoarthritis (OA) in hip and knee joints. The first metatarsophalangeal joint (1^stMTPJ) is frequently affected by OA, but it is unclear if CC occurs in the 1^stMTPJ. The aim of the present study was to analyze the prevalence of CC of the 1^stMTPJ in the general population by high-resolution digital contact radiography (DCR) and to determine its association with histological OA severity, age and body mass index (BMI).

Methods

168 metatarsal heads of 84 donors (n = 47 male, n = 37 female; mean age 62.73 years, SD ±18.8, range 20–93) were analyzed by DCR for the presence of CC. Histological OA grade (hOA) by OARSI was analyzed in the central load-bearing zone of the first metatarsal head (1^st MH). Structural equation modeling (SEM) was performed to analyze the interrelationship between CC, hOA, age and BMI.

Results

The prevalence of CC of 1^stMH was 48.8 % (41/84) (95 %-CI [37.7 %, 60.0 %]), independent of the affected side (p = 0.42), gender (p = 0.41) and BMI (p = 0.51). The mean amount of CC of one MH correlated significantly with that of the contralateral side (r_s = 0.4, 95 %-CI [0.26, 0.52], p < 0.001). The mean amount of CC (in % of total cartilage area) of the MH correlated significantly with the severity of hOA (r_s = 0.51, 95 %-CI [0.32, 0.65], p < 0.001). SEM revealed significant associations between CC and hOA (r = 0.74, p < 0.001) and between hOA and age (β = 0.62, p = 0.001), but not between CC and age (p = 0.15). There was no significant influence of BMI on either CC (p = 0.37) or hOA (p = 0.16).

Conclusion

The observation that CC of the 1^stMH is significantly associated with the severity of OA but independent of age and BMI, suggests an intimate relationship between CC and the pathogenesis of OA, the exact nature of which will have to be explored by future studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1324-0) contains supplementary material, which is available to authorized users.

Articular cartilage calcification of the humeral head is highly prevalent and associated with osteoarthritis in the general population

Articular cartilage calcification is considered a pathological albeit incompletely understood process which is known to be associated with osteoarthritis of the knee and hip. The goal of this study was to determine the prevalence of articular cartilage calcification of the shoulder as a non-weight-bearing joint and to analyze the interrelationship of calcification with age and histological severity of shoulder osteoarthritis in the general population. In a cross-sectional study of 180 humeral heads from 90 donors (n = 49 male, n = 41 female; mean age 62.7 years [20-93]), cartilage calcification of the humeral head was quantified by digital contact radiography (DCR). Histological OA grade (OARSI) was determined and structural equation modeling (SEM) was used to analyze the interrelationship of cartilage calcification, OARSI and age. The prevalence of articular cartilage calcification was 98.9% (95%CI: [93.96%, 99.97%]) and was independent of gender (p = 0.55). Cartilage calcification of one shoulder correlated significantly with that of the contralateral side (r = 0.61, 95%CI: [0.46, 0.73], p < 0.001). SEM demonstrated significant associations between histological OA grade and cartilage calcification (r = 0.55, p = 0.039), between histological OA grade and age (β = 0.59, p < 0.001) but not between age and cartilage calcification (β = 0.24, p = 0.116). In conclusion, the prevalence of shoulder cartilage calcification in the general population is higher than anticipated. The high prevalence, its concomitant bilateral manifestation and the association between the amount of cartilage calcification and OA severity, but not age, suggest that cartilage calcification is a systemically driven process with early onset in life and may be a causative factor in the pathogenesis of OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1984-1990, 2016.

Calcium orthophosphates (CaPO4): occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO4). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO4, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of CaPO4. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of CaPO4. In addition, natural CaPO4 are the major source of phosphorus, which is used to produce agricultural fertilizers, detergents and various phosphorus-containing chemicals. Thus, there is a great significance of CaPO4 for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Calcium pyrophosphate crystal deposition disease: diagnosis and treatment

Calcium pyrophosphate dihydrate crystal deposition disease (CPPD) is an inflammatory arthritis produced by the deposition of calcium pyrophosphate (CPP) crystals in the synovium and periarticular soft tissues. It is the third most common inflammatory arthritis. Diagnosis is suspected on the basis of the clinical picture and radiographic/laboratory findings. The reference standard for the diagnosis of CPPD is based on the identification of CPP crystals in synovial fluid by light microscopy, compensated polarized light microscopy, or phase contrast microscopy. Most treatment approaches for CPPD are based upon clinical experience and not upon controlled trials. They range - depending on the subtype and the characteristics of symptoms - from no treatment to interleukin-1 blockade antibodies or specific therapy for an underlying disease. This review summarizes all we know so far about the diagnosis and management of CPPD.

Do not hallow until you are out of the wood! Ultrasonographic detection of CPP crystal deposits in menisci: facts and pitfalls

PURPOSE

Ultrasonography (US) has been demonstrated to be an important tool in the diagnosis of calcium pyrophosphate (CPP) crystal deposition disease. The aim of our study was to individuate and describe possible pitfalls in US detection of such deposits in menisci.

PATIENTS AND METHODS

We enrolled all patients waiting to undergo knee replacement surgery due to osteoarthritis, for one-month period. Each patient underwent US examination of the knee, focusing on the menisci. After surgery, the menisci were examined by US, macroscopically and microscopically, using the microscopic analysis as the gold standard for CPP deposition.

RESULTS

11 menisci of 6 patients have been studied. Ex vivo examination of menisci performed better in CPP identification than in vivo examination. The possible reasons of misinterpretation or misdiagnosis of the in vivo exam were identified and are extensively described in the paper. Also a new sign of CPP crystal deposits was found.

CONCLUSIONS

This study permitted to highlight some difficulties in CPP crystal detection by US in menisci. Further studies are needed to define completely US CPP crystal aspect and to improve the sensibility and specificity of US in CPP deposition diagnosis.

Calcium orthophosphates: occurrence, properties, biomineralization, pathological calcification and biomimetic applications

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided.

Crystals, inflammation, and osteoarthritis

PURPOSE OF REVIEW

Calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are common components of osteoarthritic joint fluids and tissues. Why these crystals form and how they contribute to joint damage in osteoarthritis remain unclear. With renewed interest in inflammation as a key component of osteoarthritis the role of calcium-containing crystals in this common disease warrants re-examination.

RECENT FINDINGS

There is ample evidence supporting a pathogenic role for inflammation in osteoarthritis, and the innate immune system likely participates in this inflammatory process. Recent work reinforces the almost universal existence of calcium-containing crystals in tissues from patients with end-stage osteoarthritis. Calcium-containing crystals may contribute to inflammation in osteoarthritis tissues through their direct interactions with components of the innate immune system, as well as by inducing or amplifying other inflammatory signals.

SUMMARY

There is increasing evidence that calcium-containing crystals contribute to osteoarthritis and their inflammatory properties may mediate detrimental effects through innate immunity signals. Calcium-containing crystals may thus represent important therapeutic targets in osteoarthritis.

Determination of calcium in synovial fluid samples as an aid to diagnosing osteoarthritis

BACKGROUND

Microscopic inorganic crystals are commonly observed in the synovial fluid of patients suffering from arthritic diseases. Basic calcium phosphate (BCP) crystals are known to occur quite commonly in the joint fluid of osteoarthritis (OA) patients and are insoluble at physiological pH. Current analysis of patient synovial fluid depends on light microscopy and staining with Alizarin Red-S. Both methods cannot identify crystals < 1µm in size and are highly subjective. This article investigates the use of o-cresolphthalein complexone (OCP), a colorimetric reagent, to quantify calcium from crystals isolated from synovial fluid samples as a means of identifying the presence of BCP and, hence, improving the diagnosis of OA.

RESULTS

Inorganic crystals were isolated following degradation of the biological sample matrix with hyaluronidase. 1-M HNO(3) was used for crystal dissociation into ions and the colorimetric response of OCP to calcium was measured in a basic environment of 2-amino-2-methyl-1-propanol. The average calcium content in OA patient samples was up to 40% higher than in rheumatoid arthritis (RA) patient samples. RA samples were used as a comparison, because they are generally accepted to be crystal free. Within the OA group, higher levels of calcium were detected in three out of 12 synovial fluid samples, which correlated with a significantly greater number of BCP crystals detected during microscopic examination.

CONCLUSIONS

A simple method based on colorimetry for measurement of calcium content and semiquantification of BCP crystals in synovial fluid samples has been described. Sample pretreatment following addition of hyaluronidase proved to be effective in reducing viscosity and aiding the dissociation of BCP crystals in synovial fluid samples.

Calcium pyrophosphate dihydrate deposition disease of the spleen

Calcium pyrophosphate dihydrate deposition disease (CPPD), also known as pseudogout or chondrocalcinosis, is a variety of metabolic arthropathy caused by the deposition of calcium pyrophosphate dihydrate crystals in and around joints. Despite many case reports, extra-articular CPPD often goes unrecognized. Here, we report a unique case of pancreatic tail pseudocyst and CPPD of the spleen. To the best of our knowledge, CPPD of the spleen has not been reported in the literature.

Calcium Orthophosphates in Nature, Biology and Medicine

The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. These materials are of the special significance because they represent the inorganic part of major normal (bones, teeth and dear antlers) and pathological (i.e. those appearing due to various diseases) calcified tissues of mammals. Due to a great chemical similarity with the biological calcified tissues, many calcium orthophosphates possess remarkable biocompatibility and bioactivity. Materials scientists use this property extensively to construct artificial bone grafts that are either entirely made of or only surface-coated with the biologically relevant calcium ortho-phosphates. For example, self-setting hydraulic cements made of calcium orthophosphates are helpful in bone repair, while titanium substitutes covered by a surface layer of calcium orthophosphates are used for hip joint endoprostheses and as tooth substitutes. Porous scaffolds made of calcium orthophosphates are very promising tools for tissue engineering applications. In addition, technical grade calcium orthophosphates are very popular mineral fertilizers. Thus ere calcium orthophosphates are of great significance for humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Introduction: arthritis and myositis

In this chapter background medical information pertinent to the use of MRI and/or ultrasound in various musculoskeletal conditions is presented. Appreciation of the genetic, biochemical, histological, and immunological features of rheumatic diseases will be of benefit to the technician responsible for performing and interpreting these types of interrogations. For example, recognizing that cartilage disorder predates bone findings in osteoarthritis will help identify early versus late degenerative findings. Similarly, understanding the fibrovascular nature of rheumatoid pannus will help guide the use of more sophisticated ultrasound techniques such as power Doppler.

Anakinra is a possible alternative in the treatment and prevention of acute attacks of pseudogout in end-stage renal failure

We describe the case of a 71-year-old man with recurrent pseudogout attacks affecting multiple joints. He had end-stage renal failure that contra-indicated the use of non-steroidal anti-inflammatory drugs and was resistant to therapy with glucocorticoids. Based on the recent findings that interleukin (IL)-1beta is involved in crystal-induced inflammation, the patient received anakinra, a specific IL-1 inhibitor, in order to treat an acute attack of pseudogout. In addition, anakinra was administered as preventive therapy 3days per week after each hemodialysis session. Under this treatment, he did not present any severe episode of arthritis after a follow-up of 8 months. This observation suggests that anakinra is efficacious and safe for the prevention of crystal-induced arthritis in patients with severe renal failure.

Characterization of articular calcium-containing crystals by synchrotron FTIR

OBJECTIVE

Sixty percent of synovial fluids from patients with severe osteoarthritis (OA) contain calcium pyrophosphate dihydrate (CPPD) or basic calcium phosphate (BCP) crystals. These bioactive crystals can be particularly difficult to accurately identify in complex biologic systems, such as in vitro models of crystal formation. We sought to determine if synchrotron Fourier Transform Infrared spectroscopy (sFTIR) could be used to identify and characterize calcium-containing crystals in mineralization models.

METHODS

CPPD and BCP crystals from porcine models of crystal formation were examined with an FTIR Microscope attached to a synchrotron light source. As a comparison, crystals from human synovial fluids were also examined. The sFTIR spectra generated were compared with known spectra of multiple forms of BCP and CPPD crystals, as well as spectra generated by synthetic CPPD and BCP crystals and cartilage proteoglycans, alone and in mixtures.

RESULTS

sFTIR readily identified CPPD and BCP crystals in porcine models as well as in fresh synovial fluids. Brushite was also present in human and porcine samples, and whitlockite was seen in some porcine samples. Mixtures of minerals were commonly found in a single crystal aggregate in both human and porcine samples. In spectra from many CPPD crystals, the peak at the 1134 cm(-1) found on the standard spectrum for CPPD was diminished. Addition of spectra from cartilage proteoglycans to those of synthetic CPPD crystals dampened the peak at this frequency region, much as this peak was diminished in biologically derived CPPD crystals.

CONCLUSION

sFTIR analysis allows for accurate identification of CPPD and BCP crystals generated in vitro and will be a useful research tool to study articular crystals.

Successful treatment of resistant pseudogout with anakinra

We describe herein the case of a 63-year-old man with pseudogout affecting multiple joints that was resistant to treatment with allopurinol, steroids, and antiinflammatory drugs. Based on recent data on the molecular mechanism of pseudogout that demonstrated overproduction of interleukin-1 (IL-1), we treated the patient with anakinra, an IL-1 receptor antagonist. The patient responded to treatment with anakinra within 2 weeks, with resolution of the signs and symptoms of pseudogout and normalization of levels of inflammation markers.

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.