Familial calcium crystal diseases: what have we learned?

Calcific tendinopathy of the shoulder: clinical perspectives into the mechanisms, pathogenesis, and treatment

Calcific tendinopathy (CT) of the shoulder is a common, painful condition characterized by the presence of calcium deposits in the rotator cuff tendons. Current theories indicate that CT may be the result of a cell-mediated process in which, after a stage of calcium deposition, calcifications are spontaneously resorbed. However, in a minority of cases, this self-healing process is somehow disrupted, resulting in symptoms. Recent literature shows an emerging role of biological and genetic factors underlying CT. This new evidence could supplement the classic mechanical theory of rotator cuff tendinopathy complicated by calcium precipitation, and it may also explain why the majority of the therapies currently in use are only able to provide partially satisfactory outcomes. This review aims to summarize the current knowledge about the pathological processes underlying CT of the shoulder and thereby justify the quest for advanced biological treatments of this condition when it becomes symptomatic.

[Crystal-induced activation of the inflammasome: gout and pseudogout]

Crystals in tissues lead the innate immune system to the same kind of acute response seen with pathogens. Via activation of the inflammasome, interleukin-1 (IL-1) is released, which upregulates mediators such as cyclooxygenase, tumor necrosis factor, and IL-8 and induces an acute granulocytic inflammation. Therefore, in addition to nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, and colchicine, IL-1 blockers appear to be effective. Large clinical trials have already been initiated. Such an approach could constitute a valuable alternative for patients with contraindications or insufficient response to NSAIDs. After the attack has subsided, control of uric acid metabolism is central. At least several of the responsible urate transporters have been unraveled, which could lead to more focused therapy in the future. At present, diet and blockade of uric acid synthesis remain the main pillars of therapy. The new xanthine oxidase inhibitor febuxostat constitutes a novel option for patients with renal insufficiency or intolerance to allopurinol.

[Chondrocalcinosis and hypomagnesemia: clinical and radiological progression]

Hypomagnesemia is a rare secundary metabolic disorder associated with calcium pyrophosphate dihydrate cristal deposition disease in joint structures and may cause asymptomatic chondrocalcinosis (linear calcification of cartilage), pseudogout, and chronic arthropathy. We report 2 young men with relapsing acute knee monoarthritis with chondrocalcinosis and hypomagnesemia. After follow-up clinical and radiological events al least for 5 years and treatment with magnesium lactate, these patients have not shown new pseudogout attacks. We discuss knee radiological evolution in both patients, outstanding major knee radiological deterioration in the patient with early symptoms and a familial chondrocalcinosis association, in spite of clinical asymptomatic status.

Kristallarthropathien – alt, aber wichtig

Gout is the most common inflammatory arthropathy for men. Asymptomatic hyperuricemia, which should lead to diet, but not to medication, is much more common still. Increased uric acid levels mostly result from diminished renal excretion, which is more commonly familiar than secondary (renal failure, diuretics). With the first episode of often typical (red, hot, exquisitely painful first MTP joint) acute arthritis or with urate nephrolithiasis, increased uric acid turns pathological. Attacks are treated with NSAIDs or corticosteroids. More common attacks, chronic gout, or urate nephropathy are definite indications for long-term (at least 5 years) therapy with allopurinol or febuxostat. Additional anti-inflammatory medication will be necessary during the first months. Calcium pyrophosphate deposition arthropathy, the second common crystal-induced arthritis, is diagnosed by synovial fluid analysis or for chondrocalcinosis. Treatment for attacks resembles therapy of acute gout; causal therapy is possible in case of secondary forms (e.g. hypothyroidism. hyperparathyroidism, hemochromatosis).

Crystal deposits in the human intervertebral disc: implications for disc degeneration

BACKGROUND CONTEXT

Although crystal deposition in cartilage and synovial fluid has received much attention, crystal formation and the role that crystal deposits play are virtually unexplored in the intervertebral disc. In articular cartilage matrix, crystal deposits are associated with altered extracellular matrix (ECM) and cell phenotypic features, but crystal deposition in the human intervertebral disc has received much less attention.

PURPOSE

To determine the incidence of crystal deposits in the annulus and to evaluate associated disc cell and ECM features.

STUDY DESIGN/SETTING

Human intervertebral disc annulus tissue was obtained in a prospective study of the presence of crystals in the disc ECM. Human Subjects Institutional Review Board approved experimental studies.

PATIENT SAMPLE

Two hundred eight sequential disc specimens were submitted from surgical disc procedures performed on individuals with herniated discs, degenerative disc disease, or recurrent disc herniation. During this same time period, three disc specimens were received from nonsurgical donors and added to the study population.

OUTCOME MEASURES

Histologic features with special attention to crystal deposition.

METHODS

Specimens were processed undecalcified and examined for the histologic presence of crystal deposits and ECM features around the crystals.

RESULTS

The proportion of specimens containing crystals was determined to be 14.7%; crystals displayed varying sizes, morphology, and polarized light birefringence features. Pyrophosphate crystals were most common, but oxalate-like crystals were also present. ECM in crystal regions showed previously recognized alterations.

CONCLUSIONS

This study shows that the incidence of crystal deposits in discs is approximately 15% and is thus a relatively common occurrence. These data are important because masses of crystals not only disrupt disc ECM but may also accelerate preexisting degenerative changes via an elevation in matrix metalloproteinases (as previously recognized in cartilage). Because failure of the structural integrity of the disc can result in annular tears and subsequent disc herniation, the mechanisms of crystal formation and the relationship between crystals and disc degeneration merit further investigations.

Calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint: new developments relevant to the clinician

The major types of crystals containing calcium, which causes arthropathy and periarticular disease, are calcium pyrophosphate dihydrate and basic calcium phosphates, including hydroxyapatite. Exciting advances include the identification of mutations in the gene ANKH associated with disordered inorganic pyrophosphate (PPi) transport in some kindred with familial chondrocalcinosis linked to chromosome 5p. In addition, central basic mechanisms governing cartilage calcification and their relationship to aging and osteoarthritis have now been elucidated. These include the role of plasma cell glycoprotein-1, the PPi-generating ecto-enzyme, in chondrocalcinosis and the linkage of low- grade inflammation to expression and activation of two cartilage-expressed transglutaminase isoenzymes with direct calcification-stimulating activity. This review discusses clinically pertinent new information on pathogenesis. The authors also address, in detail, current diagnostic and therapeutic issues pertaining to calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint, as well as possible therapeutic directions for the future.

Parallels between arterial and cartilage calcification: what understanding artery calcification can teach us about chondrocalcinosis

The pathogenesis of arterial calcification and chondrocalcinosis has become concurrently illuminated in recent years. For example, both processes occur in chronic inflammation-mediated degenerative diseases associated with aging (including atherosclerosis and osteoarthritis). Both processes are also modulated by altered gene expression by resident cells and by the release of mineralization-competent cell fragments (matrix vesicles and apoptotic bodies). Among the variety of genetic diseases associated with artery calcification are disorders that also promote cartilage calcification and/or dysregulated bone formation. Our discussion highlights that pathologic arterial and articular cartilage calcification both can be owing to genetic deficiencies of calcification inhibitors such as the inorganic pyrophosphate-generating ectoenzyme PC-1/nucleotide pyrophosphatase phosphodiesterase 1. Conversely, pathologic arterial and articular cartilage calcification also can primarily arise as a consequence of active processes driven by inflammatory cytokines and by disordered calcium and inorganic phosphate homeostasis. As discussed in this review, recent developments in the pathogenesis of arterial calcification provide valuable information pertinent to potential future advances in controlling chondrocalcinosis.

Oxalate crystal deposition disease

In addition to monosodium urate, calcium pyrophosphate dihydrate, and apatite crystals, oxalate crystals are less often found in synovial fluids in association with acute or chronic arthritis. Oxalate crystal deposition disease is seen in patients with primary hyperoxaluria types 1 and 2 (PH1 and 2) and in patients with end-stage renal disease managed with long-term dialysis. Oxalate crystal deposits are found mainly in kidneys, bone, skin, and vessels, and less often inside the joints. Musculoskeletal and systemic manifestations of oxalate crystal deposition disease may be confused with those observed with the other most common types of crystal deposition diseases. Clinical and radiographic features include calcium oxalate osteopathy, acute and chronic arthropathy with chondrocalcinosis, synovial calcification, and miliary skin calcium oxalate deposits and vascular calcifications that affect mainly the hands and feet. Systemic life-threatening cardiovascular, neurologic, and hematologic manifestations are rare. Genomic DNA studies have identified those genetic defects of PH1 and PH2 that allow a precise early diagnosis. Kidney transplantation has poor outcome as a result of graft oxalosis. Combined liver and kidney transplantation is the treatment of choice in patients with PH1 and advanced renal failure. Pre-emptive isolated liver transplantation is the preferred treatment in patients who develop the disease during infancy with progressive manifestations of oxalosis. These novel findings in the understanding of the molecular and enzymatic aspects of primary hyperoxalurias have provided a more rational basis for the management and prevention of oxalate crystal deposition disease. This information may lead to a better understanding and effective management of other common calcium-containing crystal deposition diseases.

Calcium crystals in osteoarthritis

Osteoarthritis is the most common form of arthritis in adults and its incidence increases with age. More than 50% of people aged 65 and older have radiographic changes of knee osteoarthritis. Calcium crystals, including calcium pyrophosphate dihydrate and basic calcium phosphate crystals, are also common in the elderly. Not surprisingly, osteoarthritis and crystal arthropathy frequently coexist. The question of a role for calcium crystals in causing or worsening osteoarthritis has been pondered for many years. Progress in understanding the interrelationships between calcium crystals and osteoarthritis has been slowed by our limited knowledge of the pathogenesis of both osteoarthritis and calcium crystal-induced arthritis and our limited ability to accurately detect calcium crystals. Nonetheless, there are good data from clinical and laboratory studies supporting an important role for calcium crystals in osteoarthritis.

Bilateral temporomandibular joint pseudogout

Pseudogout is an acute presentation of one type of crystal deposition disease in which calcium pyrophosphate dihydrate crystals are found in the joint spaces of synovial joints. In this case, a 56-year-old caucasian male presented with right sided preauricular swelling, temporomandibular joint arthralgia and restricted mouth opening; he developed identical symptoms on the left side two days later.