Diagnosis and Treatment of Calcium Pyrophosphate Deposition (CPPD) Disease: A Review

Core domain set for chronic and/or recurrent manifestations of calcium pyrophosphate deposition disease: OMERACT delphi survey to establish consensus

OBJECTIVE

To agree on important domains for the Outcome Measures in Rheumatology (OMERACT) core domain set for chronic and/or recurrent manifestations of calcium pyrophosphate deposition (CPPD) disease.

METHODS

Patient research partners (PRPs) and other participants (mainly clinicians and researchers) contributed to three rounds of a consensus survey using Delphi methodology. Consensus was defined if ≥70% of both patients and other participants scored the domain as 'critically important domain to include'. In a subsequent ranking exercise, all participants were asked to select and rank up to 10 of the domains reaching consensus.

RESULTS

Fifteen domains reached consensus as critically important. Within the Pathophysiological Manifestations area, these were joint pain, joint tenderness, joint swelling, acute CPP crystal arthritis flare, joint damage on imaging tests, joint calcification on imaging tests, and crystals in joint fluid. Within the Life Impact area, these were overall function, ability to complete daily tasks, ability to work, health related quality of life, patient global assessment response to treatment, patient global assessment of disease activity, physician global assessment of disease activity, and patient satisfaction with treatment. No domains within the Societal/Resource Use area reached consensus as critically important. In the ranking exercise, joint pain, joint tenderness, joint swelling, acute CPP crystal arthritis flare and overall function were most highly ranked.

CONCLUSION

This work has identified potential domains for the OMERACT core domain set for chronic and/or recurrent manifestations of CPPD disease. There was strong support for joint pain, joint tenderness, joint swelling, acute CPP crystal arthritis flare, overall function, and global assessments of disease activity as core domains.

Particle uptake by macrophages triggers bifurcated transcriptional pathways that differentially regulate inflammation and lysosomal gene expression

Exposure to particles is a driver of several inflammatory diseases. Here, we investigated macrophage responses to monosodium urate crystals, calcium pyrophosphate crystals, aluminum salts, and silica nanoparticles. While each particle induced a distinct gene expression pattern, we identified a common inflammatory signature and acute activation of lysosomal acidification genes. Using monosodium urate crystals as a model, we demonstrated that this lysosomal gene program is regulated by a 5'-prime-AMP-activated protein kinase (AMPK)-dependent transcriptional network, including TFEB, TFE3, and the epigenetic regulators DNA methyl transferase 3a (DNMT3A) and DOT1L. This lysosomal acidification program operates in parallel with, but largely independently of, a JNK-AP-1-dependent network driving crystal-induced chemokine and cytokine expression. These findings reveal a bifurcation in pathways governing inflammatory and lysosomal responses, offering insights for treating particle-associated diseases.

Updates in Deposition Arthritis Other Than Gout

This article focuses on updates in calcium pyrophosphate deposition disease (CPPD) and basic calcium phosphate deposition (BCPD), highlighting recent advances in imaging and the understanding of these conditions. It explores their clinical presentations, crystal formation mechanisms, and diagnostic challenges. CPPD and BCPD are often underrecognized causes of arthritis, and recent imaging diagnostic criteria are presented.

CPP-calcification of articular cartilage is associated with elevated cytokine levels in synovial fluid

Background

Calcification of articular tissues is commonly observed in later osteoarthritis (OA) stages and can be caused by basic calcium phosphate (BCP) or calcium pyrophosphate (CPP) crystals. Calcification, particularly CPP deposition, has recently been associated with inflammation and cellular senescence. Investigating this association, we analyzed the concentration of various inflammatory mediators in synovial fluid and synovial membrane of OA patients in relation to calcification and the different crystal types.

Methods

Synovial fluid was collected from OA patients during joint replacement surgery. Cytokine concentrations were measured using magnetic bead-based multiplex assay using Luminex® technology. Radiographs were used to determine and grade calcification of the knee joint and involved calcium crystal types were identified via Raman spectroscopy.

Results

Synovial fluid of patients with radiological calcification showed elevated levels of multiple cytokines (IL-10, IL-15, IL-1ra, GM-CSF), chemokines (IL-8, MCP-1, MIP-1b) and growth factors (PDGF-AB/BB, VEGF). Crystal differentiation revealed higher synovial fluid concentrations of IL-15, IL-1ra, IL-10, GM-CSF, PDGF-AB/BB and MIP-1b in patients with CPP- compared to BCP-calcified cartilage.

Conclusion

We show an elevated cytokine profile in synovial fluid of patients with radiological calcification that may be linked to CPP depositison in cartilage.

Calcium pyrophosphate crystal deposition in the temporomandibular joint associated with temporomandibular joint surgery: Case report

INTRODUCTION

Calcium pyrophosphate crystal deposition disease, also known as pseudogout, is a condition in which calcium pyrophosphate dihydrate (CPPD) crystals accumulate in the joint tissues, causing inflammation and arthritis. CPPD crystals are known to accumulate due to trauma; however, pseudogout developing after open temporomandibular joint (TMJ) surgery has not been previously reported.

PRESENTATION OF CASE

A 54-year-old male presented to our hospital with complaints of discomfort and swelling in the front of the left ear. Magnetic resonance imaging (MRI) revealed a TMJ tumor, which was removed under general anesthesia, and a pathological diagnosis of synovial chondromatosis (SC) was established. Seven months after the surgery, recurrence was suspected based on an MRI scan. However, the patient had few subjective symptoms; therefore, we decided to continue to observe the patient without specific treatment. Twenty two months after the surgery, the mass was found to have increased in size; therefore, a second surgery was performed. Pathological examination revealed CPPD deposition, which led to the rare diagnosis of CPPD crystal deposition in the left TMJ.

DISCUSSION

The development of CPPD in this patient may have been triggered by mechanical stimulation from intra-articular free bodies. However, because CPPD was not detected in the original excised specimen, it is more likely that the surgical invasion during the original procedure promoted the deposition of CPPD crystals.

CONCLUSION

This case demonstrates the rare possibility of CPPD development after TMJ surgery. This emphasizes the importance of long-term follow-up after open TMJ surgery to monitor the possibility of CPPD-related complications.

Paravertebral crystal deposition disease: a retrospective study of clinical presentation, prevalence, and CT imaging findings

OBJECTIVES

Paravertebral crystal deposition disease, characterized by the deposition of crystals around the vertebral bodies leading to acute inflammation and pain, is a condition that remains largely unrecognized. This study aims to elucidate the prevalence, clinical features, and CT findings associated with this disease.

METHODS

We retrospectively analyzed 14,839 consecutive patients who underwent chest and/or abdominal CT (September 2017 to September 2024) owing to chest, abdominal, or back pain. Cases demonstrating paravertebral calcification with a surrounding soft tissue density of ≥ 5 mm were identified and further evaluated.

RESULTS

Twenty-four cases of paravertebral crystal deposition disease were identified, with a prevalence of 0.16% (95% CI: 0.10, 0.24). The mean age was 46.2 years, with a female predominance (n = 15, 63%). Back pain was the most common presenting symptom (n = 15, 63%). Calcifications were primarily located at the lower thoracic and upper lumbar spine (Th6/7-L1/2) in 18 cases (75%) and in the anterior median to anterior right region of the vertebral body in 21 cases (86%). Mean of maximum CT values of the crystal deposition was approximately 800 HU; in follow-up cases, the depositions either resolved or exhibited morphological changes.

CONCLUSIONS

This study adds to the current knowledge base by identifying a 0.16% prevalence of paravertebral crystal deposition disease in patients with torso pain-often overlooked in clinical practice, primarily affecting middle-aged women. CT imaging shows calcifications mainly in the lower thoracic and upper lumbar spine. Considering this self-limiting disease in differential diagnoses can improve diagnostic accuracy and patient management.

Selective Dissolution of Calcium Pyrophosphate Dihydrate Crystals Using a Pyrophosphate Specific Receptor

Pseudo-gout is caused by the deposition of highly insoluble calcium pyrophosphate dihydrate (CPPD) crystals in the joints of sufferers. This leads to inflammation and ultimately joint damage. The insolubility of CPPD is driven by the strong attraction of di-cationic calcium ions with tetra-anionic pyrophosphate ions. One of the challenges of dissolving CPPD is that a related mineral, hydroxy apatite (HA) is present in larger amounts in the form of bone and also contains strongly interacting calcium and phosphate ions. Our aim in this work was to selectively dissolve CPPD in preference to HA. To accomplish this, we used a known receptor for pyrophosphate that contains two complexed zinc ions that are ideally spaced to interact with the tetra-anion of pyrophosphate. We hypothesized that such a molecule could act as a preorganized tetra-cation that would be able to outcompete the two calcium ions present in the crystal lattice of CPPD. We demonstrate both visually and through analysis of released phosphorous that this molecule is able to preferentially dissolve CPPD over the closely related HA and thus can form the basis for a possible approach for the treatment of pseudo-gout.

Spine Pseudogout Following Breast Cancer Treatment: A Report of Two Cases

Calcium pyrophosphate disease (CPPD) is a commonly diagnosed crystal-induced disease that typically presents as acute monoarticular or oligoarticular arthritis. It is less commonly seen in the spine, and its clinical importance in this area is still relatively understudied. Isolated spinal CPPD is quite rare; a diagnosis of spinal CPPD is almost always accompanied by peripheral CPPD. We present two patients who were both being treated for breast cancer. They underwent spine surgery and were subsequently diagnosed with isolated CPPD of the spine by pathology specimens. Neither patient had a history of CPPD prior to the surgery. We hypothesize there is a potential link between breast cancer and its treatment and isolated spinal CPPD; however, more research and case reports are needed to begin making conclusions and understand the relevance.

cGAS-STING pathway in pathogenesis and treatment of osteoarthritis and rheumatoid arthritis

Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are significant health concerns with notable prevalence and economic impact. RA, affecting 0.5% to 1.0% of the global population, leads to chronic joint damage and comorbidities. OA, primarily afflicting the elderly, results in joint degradation and severe pain. Both conditions incur substantial healthcare expenses and productivity losses. The cGAS-STING pathway, consisting of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), is a crucial component of mammalian immunity. This pathway is responsible for detecting foreign DNA, particularly double-stranded DNA (dsDNA), triggering innate immune defense responses. When cGAS recognizes dsDNA, it catalyzes the synthesis of cyclic GMP-AMP (cGAMP), which then binds to and activates STING. Activated STING, in turn, initiates downstream signaling events leading to the production of interferons and other immune mediators. The cGAS-STING pathway is essential for defending against viral infections and maintaining cellular balance. Dysregulation of this pathway has been implicated in various inflammatory diseases, including arthritis, making it a target for potential therapeutic interventions. Understanding the intricate molecular signaling network of cGAS-STING in these arthritis forms offers potential avenues for targeted therapies. Addressing these challenges through improved early detection, comprehensive management, and interventions targeting the cGAS-STING pathway is crucial for alleviating the impact of OA and RA on individuals and healthcare systems. This review offers an up-to-date comprehension of the cGAS-STING pathway's role in the development and therapeutic approaches for these arthritis types.

The basics of phosphate metabolism

Phosphorus is an essential mineral that is, in the form of inorganic phosphate (Pi), required for building cell membranes, DNA and RNA molecules, energy metabolism, signal transduction and pH buffering. In bone, Pi is essential for bone stability in the form of apatite. Intestinal absorption of dietary Pi depends on its bioavailability and has two distinct modes of active transcellular and passive paracellular absorption. Active transport is transporter mediated and partly regulated, while passive absorption depends mostly on bioavailability. Renal excretion controls systemic Pi levels, depends on transporters in the proximal tubule and is highly regulated. Deposition and release of Pi into and from soft tissues and bone has to be tightly controlled. The endocrine network coordinating intestinal absorption, renal excretion and bone turnover integrates dietary intake and metabolic requirements with renal excretion and is critical for bone stability and cardiovascular health during states of hypophosphataemia or hyperphosphataemia as evident from inborn or acquired diseases. This review provides an integrated overview of the biology of phosphate and Pi in mammals.

Titanium Dioxide Promotes the Growth and Aggregation of Calcium Phosphate and Monosodium Urate Mixed Crystals

The increased utilization of titanium dioxide (TiO2) nanoparticles (TNPs) in various industrial and consumer products has raised concerns regarding its harmful effect due to its accumulation within the different systems of the human body. Here, we focused on the influence of TNPs on the growth and aggregation of two crucial crystalline substances, calcium phosphate (CaP) and monosodium urate (MSU), particularly its implications in gout disease. In this study, we adopted microscopic techniques and generated kinetic models to examine the interactions between TNPs, CaP and MSU, and crystallization, under controlled laboratory conditions. Our findings reveal that TNPs not only facilitate the growth of these crystals but also promote their co-aggregations. Crystal dissolution kinetics also exhibit that an increase in TNPs concentration corresponds to a reduction in the dissolution rate of CaP and MSU crystals in presence of the dissoluting agent hydroxycitrate (Hcit). These observations suggest that TNPs can stabilize CaP+MSU mixed crystals, which underscores the significance of TNPs' exposure in the pathogenesis of gout disease.

The Ageing Foot

Feet suffer significant stress throughout a lifetime and undergo ageing-associated problems due to gradual tissue degeneration affecting the skin, connective tissue, and nerves. Oxygen supply to the tissues may be diminished. The skin gets dry and calluses, ulcers and fungal infections of the skin and nails are not uncommon. Ligaments and tendons degenerate and, without proper prevention, deformities including claw toes, hammer toes, tendonitis, and bursitis may occur. Skeletal toe deformities such as bunions, bony spurs, and hallux valgus may increase discomfort, while stress fractures may have an adverse impact on the patients' quality of life. The ageing foot pathology may add up to common age-related problems, such as crystal deposition arthropathies, diabetes mellitus, peripheral circulatory disorders, and peripheral edema, increasing morbidity. This review summarizes ageing-related feet problems, focusing on prevention and treatment. Foot health has a paramount role in overall wellbeing, therefore prevention, proper foot care, and prompt diagnosis and management of ageing-related changes are vital for maintaining a healthy, active status.