Intracellular and extracellular CPPD crystals are a regular feature in synovial fluid from uninflamed joints of patients with CPPD related arthropathy

Synovial Fluid from Patients with Osteoarthritis Shows Different Inflammatory Features Depending on the Presence of Calcium Pyrophosphate Crystals

The role of calcium pyrophosphate (CPP) crystals in osteoarthritis (OA) is still a matter of debate. With this study we aimed to investigate the inflammatory features of synovial fluid (SF) collected from patients with OA with CPP crystals compared with those without crystals. We also explored the effect of OA SF on monocytes response. SFs were collected from adult patients with OA and subdivided according to the presence of crystals. Local cellular and humoral inflammatory mediators were analysed in the SF samples. The expression levels of IL-1β, IL-18, CASP-1, NLRP3, and GAPDH were measured by RT-PCR in the cells obtained by pelleting the SF samples. For the in vitro study, a monocytic cell line was treated with selected SF samples. SF with CPP crystals showed a significant increase in inflammatory cellular indices and higher levels of IL-1β, IL-8, and caspase-1 transcript with respect to SF without crystals. Higher concentrations of VEGF were also observed in the early stages of the whole OA patients. THP-1 cells stimulated with OA SF released a significant amount of IL-1 β in culture supernatants. This study demonstrated that SF collected from patients with OA shows different inflammatory features depending on the presence of CPP crystals.

Risk of cardiovascular events in patients having had acute calcium pyrophosphate crystal arthritis

OBJECTIVES

Calcium pyrophosphate deposition (CPPD) disease, broadly defined, has been associated with increased risk of cardiovascular (CV) events. We investigated risk of CV events in patients with acute CPP crystal arthritis, the acute manifestation of CPPD.

METHODS

Cohort study using Mass General Brigham electronic health record (EHR) data, 1991-2017. Patients with acute CPP crystal arthritis were identified using a published machine learning algorithm with positive predictive value 81%. Comparators were matched on year of EHR entry and index date of patients with acute CPP crystal arthritis (first positive synovial fluid CPP result or mention of 'pseudogout', or matched encounter). Major adverse cardiovascular event (MACE) was a composite of non-fatal CV event (myocardial infarction, acute coronary syndrome, coronary revascularisation, stroke) and death. We estimated incidence rates (IRs) and adjusted hazard ratios for MACE, non-fatal CV event and death, allowing for differential estimates during years 0-2 and 2-10. Sensitivity analyses included: (1) patients with acute CPP crystal arthritis diagnosed during outpatient visits, (2) patients with linked Medicare data, 2007-2016 and (3)patients matched on number of CV risk factors.

RESULTS

We matched 1200 acute CPP crystal arthritis patients to 3810 comparators. IR for MACE in years 0-2 was 91/1000 person-years (p-y) in acute CPP crystal arthritis and 59/1000 p-y in comparators. In years 2-10, IR for MACE was 58/1000 p-y in acute CPP crystal arthritis and 53/1000 p-y in comparators. Acute CPP crystal arthritis was significantly associated with increased risk for MACE in years 0-2 (HR 1.32, 95% CI 1.01 to 1.73) and non-fatal CV event in years 0-2 (HR 1.92, 95% CI 1.12 to 3.28) and years 2-10 (HR 2.18, 95% CI 1.27 to 3.75), but not death. Results of sensitivity analyses were similar to the primary analysis; in the outpatient-only analysis, risk of non-fatal CVE was significantly elevated in years 2-10 but not in years 0-2.

CONCLUSIONS

Acute CPP crystal arthritis was significantly associated with elevated short and long-term risk for non-fatal CV event.

Identification of Common Pathogenic Pathways Involved in Hemochromatosis Arthritis and Calcium Pyrophosphate Deposition Disease: a Review

OBJECTIVES

Arthritis is a common clinical manifestation of hereditary hemochromatosis (HH), and HH is one of a handful of conditions linked to calcium pyrophosphate deposition (CPPD) in joints. The connection between these two types of arthritis has not yet been fully elucidated. In light of new pathogenic pathways recently implicated in CPPD involving bone, we reviewed the literature on the etiology of hemochromatosis arthropathy (HHA) seeking shared pathogenic mechanisms.

RESULTS

Clinical observations reinforce striking similarities between HHA and CPPD even in the absence of CPP crystals. They share a similar joint distribution, low grade synovial inflammation, and generalized bone loss. Excess iron damages chondrocytes and bone cells in vitro. While direct effects of iron on cartilage are not consistently seen in animal models of HH, there is decreased osteoblast alkaline phosphatase activity, and increased osteoclastogenesis. These abnormalities are also seen in CPPD. Joint repair processes may also be impaired in both CPPD and HHA.

CONCLUSIONS

Possible shared pathogenic pathways relate more to bone and abnormal damage/repair mechanisms than direct damage to articular cartilage. While additional work is necessary to fully understand the pathogenesis of arthritis in HH and to firmly establish causal links with CPPD, this review provides some plausible hypotheses explaining the overlap of these two forms of arthritis.

Ultra-high resolution 3D MRI for chondrocalcinosis detection in the knee-a prospective diagnostic accuracy study comparing 7-tesla and 3-tesla MRI with CT

OBJECTIVES

To test the diagnostic accuracy of a 3D dual-echo steady-state (DESS) sequence at 7-T MRI regarding the detection of chondral calcific deposits of the knee in comparison to 3-T MRI, using CT as cross-sectional imaging reference standard.

METHODS

CT and 7-T MRI (DESS) of knee joints in 42 patients with radiographically known chondrocalcinosis (13 of 42 bilateral) were prospectively acquired for all included patients (n = 55 knee joints). Additionally, 3-T MRI (DESS) was performed for 20 of these 55 knee joints. Two fellowship-trained musculoskeletal radiologists scored eight cartilage regions of each knee joint separately regarding presence of cartilage calcification, diagnostic confidence level, and sharpness of calcific deposits. In an explorative subanalysis, micro-CT of the menisci was evaluated after knee arthroplasty in one patient. Diagnostic performance metrics and nonparametric tests were used to compare between modalities. p values < 0.05 were considered to represent statistical significance.

RESULTS

Sensitivity for chondrocalcinosis detection was significantly higher for 7-T MRI (100%) compared to 3-T MRI (reader 1: 95.9%, p = 0.03; reader 2: 93.2%, p = 0.002). The diagnostic confidence was significantly higher for both readers at 7 T compared to both 3-T MRI (p < 0.001) and to CT (p = 0.03). The delineation of chondral calcifications was significantly sharper for 7-T compared to both 3-T MRI and CT (p < 0.001, both readers). Micro-CT in one patient suggested that 7-T MRI may potentially outperform standard CT in diagnosing chondral calcifications.

CONCLUSION

3D-DESS imaging at 7-T MRI offers a significantly higher sensitivity in detection of chondral calcific deposits compared to 3-T MRI.

KEY POINTS

• 3D dual-echo steady-state (DESS) MRI at 7 T has a higher sensitivity in detection of chondral calcific deposits compared to 3-T MRI (p ≤ 0.03). • 3D DESS MRI at 7 T yields no false-negative cases regarding presence of chondral calcific deposits. • 3D DESS MRI at 7 T offers better delineation and higher diagnostic confidence in detection of chondral calcific deposits compared to 3-T MRI (p < 0.001).

The diagnostic value of conventional radiography and musculoskeletal ultrasonography in calcium pyrophosphate deposition disease: a systematic literature review and meta-analysis

OBJECTIVE

To examine and compare the accuracy of conventional radiography (CR) and musculoskeletal ultrasonography (US) in the diagnosis of calcium pyrophosphate (CPP) crystals deposition disease (CPPD).

DESIGN

A systematic search of electronic databases (PubMed, Embase, and Cochrane), conference abstracts and reference lists was undertaken. Studies which evaluated the accuracy of CR and/or US in the diagnosis of CPPD, using synovial fluid analysis (SFA), histology or classification criteria as reference tests were included. Subgroup analyses by anatomic site and by reference test were performed.

RESULTS

Twenty-six studies were included. Using SFA/histology as reference test, CR and US showed an excellent (CR AUC = 0.889, 95%CI = 0.811-0.967) and an outstanding (US AUC = 0.954, 95%CI = 0.907-1.0) diagnostic accuracy (p < 0.01), respectively. Furthermore, US showed a higher sensitivity (0.85, 95%CI = 0.79-0.90 vs 0.47, 95%CI = 0.40-0.55) and only a little lower specificity (0.87, 95%CI = 0.83-0.91 vs 0.95, 95%CI = 0.92-0.97) than CR. A considerable heterogeneity between the studies was found, with adopted reference test being the main source of heterogeneity. In fact, subgroup analysis showed a significant change in the diagnostic accuracy of CR, but not of US, using Ryan and McCarty criteria or SFA/histology as reference test (CR: AUC = 0.956, 95%CI = 0.925-1.0 vs AUC = 0.889, 95%CI = 0.828-0.950, respectively, p < 0.01) (US: AUC = 0.922, 95%CI = 0.842-1.0 vs AUC = 0.957, 95%CI = 0.865-1.0, respectively, p = 0.08) CONCLUSIONS: Although US is more sensitive and a little less specific than CR for identifying CPP crystals, both these two techniques showed a great diagnostic accuracy and should be regarded as complementary to each other in the diagnostic work-up of patients with CPPD.

There is no difference in postoperative pain, function and complications in patients with chondrocalcinosis in the outcome of total knee arthroplasty for end-stage osteoarthritis

PURPOSE

Chondrocalcinosis is the radiographic appearance of calcium crystals in cartilage and other soft tissue. It is suggested that preoperative chondrocalcinosis predicts a worse outcome after total knee arthroplasty and it is unclear if chondrocalcinosis leads to more postoperative complications. This study aimed to compare function, pain, postoperative complications, postoperative signs of acute arthritis and revision rates between patients with and without chondrocalcinosis undergoing total knee arthroplasty for osteoarthritis.

METHODS

In this retrospective cohort study performed in 2017, 408 knees in 392 patients (16 bilateral total knee arthroplasties) were included. None of the patients received additional synovectomy. PROMs were evaluated after 1 year (n = 294) and 5 years (n = 308). The follow-up for clinical data was 5 years (n = 408). The range of final follow-up was 57-84 months. All preoperative radiographs were scored for chondrocalcinosis and Oxford Knee Score, Knee Society Score and Algofunctional Index were used to assess outcome. All clinical records were screened for postoperative complications (excessive wound discharge, infection, loosening, PAO, stiffness), arthritis after surgery and reoperation or revision for any reason.

RESULTS

Sixty-three knees (15.4%) showed signs of chondrocalcinosis. Male gender, higher age and lower BMI were risk factors for chondrocalcinosis. No difference was found in Oxford Knee Score, Knee Society Score and Algofunctional Index, nor in postoperative complications, postoperative signs of acute arthritis and revision rate.

CONCLUSION

Patients with and without chondrocalcinosis have the same outcome after total knee arthroplasty related to pain, functionality, complications, arthritis and revision after surgery for end-stage osteoarthritis. Chondrocalcinosis is not a contraindication for total knee arthroplasty and additional synovectomy is unnecessary.

LEVEL OF EVIDENCE

III.

Bilateral hamstring origin calcification: rare presentation of Gitelman syndrome

This case report is the first case to our knowledge of intratendinous or peritendinous calcification reported in Gitelman syndrome (GS) patients. GS represents the clinical manifestations of inactivation of the Slc12a3 genes encoding the thiazide-sensitive sodium chloride cotransporter and the Trpm6-Mg genes encoding the magnesium transporters in the distal convoluted tubule. Hence, the biochemical findings resemble those with thiazide diuretics such as hypokalaemia, hypomagnesaemia, hypocalciuria, metabolic alkalosis and low normal blood pressure. Serum calcium and phosphate levels are usually unaffected in GS unless associated with hyperparathyroidism or other hypercalcaemic aetiologies. We report a 69-year-old male patient with a history of GS who presented with bilateral ischial tuberosity tenderness. Further investigations confirmed the calcification of bilateral hamstring origin. Chondrocalcinosis is a known association of GS; however, extra-articular calcification is rare. Literature review illustrates sclerochoroidal calcification as the only reported soft tissue calcification apart from chondrocalcinosis.

Methotrexate: should it still be considered for chronic calcium pyrophosphate crystal disease?

Chronic calcium pyrophosphate crystal arthritis is a clinical consequence of the formation and deposition of these crystals in joints and can result in persistent arthritis. Curative treatment would require the removal of crystals from joints and tissues, but to date all agents tested have proven ineffective. Management of the inflammatory manifestations of chronic calcium pyrophosphate disease includes glucocorticoids, non-steroidal anti-inflammatory drugs, or colchicine, and responses are usually satisfactory. However, in some patients, the response to these agents is poor or they are contraindicated. Methotrexate had been reported as a promising option in small case series; however, in a recent issue of Arthritis Research & Therapy, a clinical trial failed to confirm the anticipated benefits. Here, we discuss some issues that might have influenced the results of the study, before deciding to abandon methotrexate as a therapeutic option for patients with chronic calcium pyrophosphate arthritis.

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.

The cytospin technique improves the detection of calcium pyrophosphate crystals in synovial fluid samples with a low leukocyte count

In synovial fluids (SF) with low leukocyte or/and crystal counts, important features may be missed, if exclusively smears are examined by polarized microscopy. That may be overcome by cytocentrifuges, which use low-speed centrifugal force to concentrate cells onto a glass slide and thus enhance the number of cells per high power field (HPF). We compared the calcium pyrophosphate (CPP) crystal counts in cytospin preparations with those in common smears of SF. The number of CPP crystals was counted in 50 SF samples by polarized microscopy, and statistical comparisons of the mean values of the cytospin and smear preparations were performed using the Wilcoxon test. The reproducibility within the slides of the cytocentrifuge and smear samples was determined by Spearman's rank correlation. The crystal counts were significantly higher in the cytospin than in the smear preparations (median 96/10 HPF vs. 2.5/10 HPF, p < 0.0001). The correlation in the crystal count between the slides 1 and 2 was significantly higher within the cytocentrifuge than in the smear group (0.97 vs. 0.73, p = 0.0004). CPP-negative cytospin preparations in initially smear-positive slides were not observed. We confirmed that the cytospin technique significantly enhances the number of examinable crystals per HPF, compared to common smears.

Comparison of three imaging techniques in diagnosis of chondrocalcinosis of the knees in calcium pyrophosphate deposition disease

OBJECTIVE

To study the role of different imaging modalities, ultrasonography, conventional radiography (CR) and CT, in visualization of chondrocalcinosis of the knees in patients with CPDD.

METHODS

Twenty-five patients (14 males and 11 females) with CPDD were enrolled in the study. Diagnosis was made according to D.J. McCarty classification criteria. All patients had arthritis of the knee and underwent aspiration of SF from the knee and microscopic investigation of SF samples. Diagnosis of CPDD was crystal proven. Three imaging methods were performed in patients: CR, CT and US of the knees.

RESULTS

CR of the knee confirmed cartilage calcification (CC) in 13 patients, CT in 18 patients and US in 25 patients. No difference in age or disease duration between patients with CC detected by different imaging methods was found.

CONCLUSION

US appeared to be a helpful tool, possibly better than CR or CT, in revealing CC in patients with CPDD. Informativity of CT and CR in the detection of CC is almost equal.

The detection of calcium pyrophosphate crystals in sequential synovial fluid examinations of patients with osteoarthritis: once positive, always positive

The aim of this study was to investigate whether calcium pyrophosphate dihydrate (CPPD) crystals are constantly detectable in sequential synovial fluid (SF) examinations of patients with initially CPPD-positive osteoarthritis (OA). For this purpose, we searched our SF database for CPPD-positive patients, who had two or more SF analyses between 2008 and 2012 to get sequential information. The database contains SF data determined by a standardised procedure. Of 1,878 samples, examined within the defined time period, 60 samples from sequential SF analyses of 23 patients were eligible for this study. The number of examinations ranged from 2 to 7 (median, 2), and the median interval between the first and last arthrocentesis was 12 months (2-43). CPPD crystals were detected in all of the sequentially examined samples according to the defined criterion of positivity. All of the subjects had OA of the knee, with a median Kellgren-Lawrence grade of 3 in the initially performed X-rays, and meniscal calcifications were found in six subjects. In conclusion, our results suggest that CPPD crystals are a regular feature of sequentially examined SF of initially CPPD-positive patients with symptomatic OA of the knee.

Methotrexate is an option for patients with refractory calcium pyrophosphate crystal arthritis

BACKGROUND

Patients with calcium pyrophosphate deposition disease sometimes require a continuous therapy. Nonsteroidal anti-inflammatory drugs, colchicine, and glucocorticoids are commonly used with good results, but occasionally, these are ineffective, contraindicated, or not tolerated. We present our experience with methotrexate (MTX) in refractory CPP arthritis.

METHODS

An observational study to describe and evaluate the use of MTX in refractory calcium pyrophosphate deposition disease was undertaken. Ten patients were included. Treatment response was evaluated by the physician (excellent, good, medium, poor, or absent response) and the patient as measured on a 10-cm visual analog scale (0 = no effect; 10 = complete resolution of symptoms). Adverse effects were recorded on all patients.

RESULTS

Five patients presented a persistent polyarthritis, 3 presented a persistent oligoarthritis, and 2 presented a very frequently recurring monoarthritis. Median MTX evaluation by patients on visual analog scale was 7.4, and physicians considered excellent (n = 2), good (n = 5), or medium (n = 3). The safety profile was generally good, but MTX was discontinued in 2 patients because of adverse effects (transient bone marrow aplasia and elevation of liver enzymes).

CONCLUSIONS

Methotrexate could be an effective and safe option for patients with refractory CPP arthritis, but additional studies are necessary to determine to what extent and for which patients MTX is effective.

Clinical anatomy of the knee

The clinical anatomy of several pain syndromes of the knee is herein discussed. These include the iliotibial tract syndrome, the anserine syndrome, bursitis of the medial collateral ligament, Baker's cyst, popliteus tendon tenosynovitis and bursitis of the deep infrapatellar bursa. These syndromes are reviewed in terms of the structures involved and their role in knee physiology. All of the discussed structures can be identified in their normal state and more so when they are affected by disease. The wealth of information gained by cross examination of the medial, lateral, posterior and anterior aspects of the knee brings to life knowledge acquired at the dissection table, from anatomical drawings and from virtual images.

Synovial fluid analysis for crystals

PURPOSE OF REVIEW

Describe why this review is timely and relevant. Identifying monosodium urate (MSU) and calcium pyrophosphate dehydrate (CPPD) crystals allows a quick and definitive diagnosis of both gout and CPPD arthritis, and remains the accepted gold standard. These diseases are still often diagnosed on inaccurate clinical grounds. Crystal identification has received little critical attention since its introduction, and it appears necessary to review the technique paying special attention to the possible reasons which deter clinicians.

RECENT FINDINGS

Describe the main themes in the literature covered by the article. Synovial fluid analysis for crystals is a simple procedure allowing immediate and definite diagnosis of gout and CPPD arthritis when clinics are fitted with a proper microscope and the rheumatologists appropriately trained. This review also illustrates how crystal analysis in synovial fluid can be initially approached with both the widely available ordinary light microscope and a simple polarized one and with good results.

SUMMARY

This study describes the implications of the findings for clinical practice or research. We hope that those not performing synovial fluid analysis will be stimulated to acquire or perfect the technique and obtain a compensated polarized microscope to comply with current standards.

Soft tissue pathology of the ankle

Derangements of the soft tissues within the ankle joint are associated with a wide variety of pathophysiology, and typically can be classified as secondary to traumatic injury, rheumatic disease, or congenital lesions. Patients often present with persistent pain, swelling, and limitations on function, usually focused on the anterior aspect of the joint. Evaluation should be guided by a detailed history and physical examination, followed by clinical, laboratory, and imaging studies as indicated. The pathophysiology, diagnosis, and management of these conditions will be the focus of this article.

Pathophysiology of articular chondrocalcinosis--role of ANKH

Calcium pyrophosphate (CPP) crystal deposition (CPPD) is associated with ageing and osteoarthritis, and with uncommon disorders such as hyperparathyroidism, hypomagnesemia, hemochromatosis and hypophosphatasia. Elevated levels of synovial fluid pyrophosphate promote CPP crystal formation. This extracellular pyrophosphate originates either from the breakdown of nucleotide triphosphates by plasma-cell membrane glycoprotein 1 (PC-1) or from pyrophosphate transport by the transmembrane protein progressive ankylosis protein homolog (ANK). Although the etiology of apparent sporadic CPPD is not well-established, mutations in the ANK human gene (ANKH) have been shown to cause familial CPPD. In this Review, the key regulators of pyrophosphate metabolism and factors that lead to high extracellular pyrophosphate levels are described. Particular emphasis is placed on the mechanisms by which mutations in ANKH cause CPPD and the clinical phenotype of these mutations is discussed. Cartilage factors predisposing to CPPD and CPP-crystal-induced inflammation and current treatment options for the management of CPPD are also described.

Association between crystals and cartilage degeneration in the ankle

OBJECTIVE

Monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals have been observed in synovial joints both before and after the onset of osteoarthritis (OA). The relationship between crystals and OA, however, remains controversial. We compared histologic and immunohistochemical patterns in articular cartilage of ankle joints with and without crystals.

METHODS

A sample of 7,855 human cadaveric tali was examined for the presence of surface and beneath-the-surface crystals. A random subsample of tali with and without crystals underwent crystal analysis by Fourier transform infrared spectroscopy (FTIR), histologic examination, and immunohistochemistry for S100 protein, superficial zone protein, collagen X, cSRC.

RESULTS

The prevalence of grossly visible crystals in the pool of donors over 18 years of age was 4.7% and correlated with advanced age, male sex, and obesity. Crystals were strongly associated with cartilage lesions and these lesions appeared to be biomechanically induced, being located where opposing articular surfaces might not be in congruence with each other. Thirty-four percent of the random subsamples of crystals upon which FTIR was performed contained CPPD, and the remainder were MSU crystals. Both crystal types were associated with higher levels of superficial zone protein and collagen X.

CONCLUSION

We show that the presence of surface crystals of either MSU or CPPD is strongly correlated with cartilage lesions in the talus. The histologic similarities in cartilage from joints with CPPD crystals compared to those with MSU crystals, together with what is known about the dramatically different etiologic factors producing these crystals, strongly suggest that these lesions are biomechanically induced.

Identification of nanobacteria in human arthritic synovial fluid by method validated in human blood and urine using 200 nm model nanoparticles

Earlier we introduced a biosensor for the identification of nanobacteria in water drops. Here, we generalize its principle and apply it to identify nanobacteria in synovial fluid from a patient with osteoarthritis. Results indicate the prevalence of nanobacteria in the synovial fluid. The identification method is applicable to body fluids such as unfiltered human blood and urine, is independent of culturing procedures, and permits for a rapid detection of nanoparticles in liquid drops. In view of increasing clinical evidence on a contribution of nanobacteria in disease, their reported detection in HIV-infected people in South Africa, laboratory experiments indicating the excretion of viable (i.e., propagating) nanobacteria from humans via urine, the use of human excreta in agricultural irrigation, models predicting an injection of nanoaerosols contained in irrigation water enriched with human excreta into the atmosphere, and the identification of nanobacteria in the terrestrial atmosphere, promote the identification method described in this work to an important tool to monitor nanobacteria in body fluids and environmental samples.

Update in calcium deposition diseases

PURPOSE OF REVIEW

Calcium pyrophosphate dihydrate and basic calcium phosphate crystals are common components of osteoarthritic synovial fluids and define subsets of patients with inflammatory or rapidly destructive arthritis. Recent literature concerning clinical and etiologic aspects of calcium pyrophosphate dihydrate and basic calcium phosphate crystal arthritis are reviewed.

RECENT FINDINGS

Recent literature reminds us of the propensity of calcium pyrophosphate dihydrate deposition disease to mimic other syndromes affecting the elderly. Several new studies reinforce the prevalence and significance of extra-articular calcium pyrophosphate dihydrate deposits, and demonstrate the presence of basic calcium phosphate-like whitlockite crystals in intervertebral discs. Current work serves to increase our appreciation for the complex role of the putative pyrophosphate transporter, ANKH, in healthy and diseased cartilage. The application of newer radiographic techniques to the diagnosis of calcium pyrophosphate dihydrate deposition disease holds promise for easier and more accurate identification of these crystal deposits in vivo. Work demonstrating the efficacy of a crystal poison in an animal model of osteoarthritis provides good evidence for a pathogenic role of calcium crystals in osteoarthritis, and hope for new therapies for these diseases.

SUMMARY

Continued work will further our understanding of these common crystals and their associated clinical syndromes.