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Calcium pyrophosphate deposition disease

Author/s: 
Timothy S.H. Kwok, Gregory Choy

Calcium pyrophosphate deposition (CPPD) disease is caused by CPP crystal accumulation in musculoskeletal tissues, leading to inflammation
Symptomatic CPPD disease (formerly known as “pseudogout”) is more common in older than younger adults and typically affects joints with previous damage. Chondrocalcinosis visible on radiographs affects 10% of adults and 50% of those older than 80 years, but most people are asymptomatic and findings are noted incidentally.1

The most common presentation is acute inflammatory monoarthritis affecting the wrists or knees, which resolves within 4 weeks
Extra-articular structures can also be affected, leading to acute inflammatory tendinitis. Crowned dens syndrome comprises 5% of CPPD disease presentations and can mimic bacterial meningitis, manifesting with acute cervical neck pain, fever, and elevated inflammatory markers with CPPD at C1 to C2, seen on computed tomography. The chronic (> 3 mo) inflammatory phenotype presents with hand or wrist symmetric polyarthritis, or with recurrent flares, and can be misdiagnosed as seronegative rheumatoid arthritis. Calcium pyrophosphate deposition disease and osteoarthritis can co-exist — underlying CPPD disease should be considered in patients with osteoarthritis at atypical locations (e.g., metacarpophalangeal joints, wrists, ankles, shoulders, elbows).2

Diagnosis can be confirmed with CPP crystals identified from synovial fluid, or the presence of the crowned dens syndrome
Although used for research, the 2023 Classification Criteria have high sensitivity (99.2%) and specificity (92.5%), thereby providing a diagnostic framework.2 Supportive diagnostic features include acute knee or wrist inflammatory arthritis in an older adult, osteoarthritis at atypical areas, or CPPD on imaging.3

Patients younger than 60 years at diagnosis should be assessed for associated metabolic diseases
Investigations for secondary causes of CPPD disease include calcium (hypercalcemia), parathyroid hormone (hyperparathyroidism), ferritin, transferrin saturation (hemochromatosis), magnesium (hypomagnesemia), and alkaline phosphatase (hypophosphatasia).2

Corticosteroids, colchicine, and nonsteroidal antiinflammatory drugs can treat acute flares4
Inflammatory arthritis lasting more than 3 months or recurrent flares (> 2/yr) should prompt rheumatology referral for consideration of chronic suppressive colchicine, hydroxychloroquine, or methotrexate (Appendix 1, available at www.cmaj.ca/lookup/doi/10.1503/cmaj.250933/tab-related-content).5

Keywords 
pseudogout calcium pyrophosphate deposition disease

Systemic Lupus Erythematosus: A Review

Author/s: 
Siegel, C.H., Sammaritano, L.R.

Importance
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by inflammation and immune-mediated injury to multiple organ systems, including the mucocutaneous, musculoskeletal, hematologic, and kidney systems. Approximately 3.4 million people worldwide have received a diagnosis of SLE.

Observations
Approximately 90% of people with SLE are female. Although there are no uniformly accepted diagnostic criteria for SLE, the 2019 European Alliance of Associations for Rheumatology (formerly the European League Against Rheumatism)/American College of Rheumatology classification criteria developed for scientific study are an estimated 96.1% sensitive and 93.4% specific for SLE. These classification criteria include both clinical factors, such as fever, cytopenia, rash, arthritis, and proteinuria, which may be indicative of lupus nephritis; and immunologic measures, such as SLE-specific autoantibodies and low complement levels. Approximately 40% of people with SLE develop lupus nephritis, and an estimated 10% of people with lupus nephritis develop end-stage kidney disease after 10 years. The primary goal of treatment is to achieve disease remission or quiescence, defined by minimal symptoms, low levels of autoimmune inflammatory markers, and minimal systemic glucocorticoid requirement while the patient is treated with maintenance doses of immunomodulatory or immunosuppressive medications. Treatment goals include reducing disease exacerbations, hospitalizations, and organ damage due to the disease or treatment toxicity. Hydroxychloroquine is standard of care for SLE and has been associated with a significant reduction in mortality. Treatments in addition to hydroxychloroquine are individualized, with immunosuppressive agents, such as azathioprine, mycophenolate mofetil, and cyclophosphamide, typically used for treating moderate to severe disease. Three SLE medications were recently approved by the Food and Drug Administration: belimumab (for active SLE in 2011 and for lupus nephritis in 2020), voclosporin (for lupus nephritis), and anifrolumab (for active SLE).

Conclusions and Relevance
Systemic lupus erythematosus is associated with immune-mediated damage to multiple organs and increased mortality. Hydroxychloroquine is first-line therapy and reduces disease activity, morbidity, and mortality. When needed, additional immunosuppressive and biologic therapies include azathioprine, mycophenolate mofetil, cyclophosphamide, belimumab, voclosporin, and anifrolumab.

Keywords 
Kidney Lupus Erythematosus Lupus Nephritis Kidney Failure
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