Calcium Pyrophosphate Deposition Disease

Calcium pyrophosphate deposition (CPPD) disease is the family of joint conditions caused by deposition of calcium pyrophosphate dihydrate crystals in articular cartilage and surrounding tissues. It spans a spectrum from asymptomatic chondrocalcinosis seen on imaging, through acute flares (pseudogout), to a chronic inflammatory arthritis, and it is a common cause of arthritis in older adults.

Definition

Calcium pyrophosphate deposition disease is an arthropathy caused by the deposition of calcium pyrophosphate dihydrate crystals in cartilage and joint tissues, presenting as asymptomatic chondrocalcinosis, acute calcium pyrophosphate crystal arthritis (pseudogout), or chronic calcium pyrophosphate crystal inflammatory arthritis.

Scope

This entry is the detailed disease node for calcium pyrophosphate deposition disease: its crystal pathophysiology, its clinical spectrum and standardised terminology, how it is diagnosed and distinguished from gout and other arthritides, its strong link to ageing and osteoarthritis, and its recognised metabolic associations. The acute pseudogout presentation is treated more fully in the companion pseudogout-cppd topic. This is reference material, not clinical guidance.

Key concepts

• Calcium pyrophosphate dihydrate crystals
• Inorganic pyrophosphate metabolism in cartilage
• Chondrocalcinosis on radiography and ultrasound
• Acute CPP crystal arthritis (pseudogout)
• Chronic CPP crystal inflammatory arthritis
• Standardised CPPD terminology
• Association with osteoarthritis and ageing
• Secondary CPPD (e.g. haemochromatosis, hyperparathyroidism, hypomagnesaemia)

Mechanisms

Calcium pyrophosphate deposition disease originates in the cartilage, where dysregulated handling of inorganic pyrophosphate favours formation of calcium pyrophosphate dihydrate crystals within the matrix. These crystals may remain clinically silent — visible only as chondrocalcinosis on imaging — or be released into the joint, where innate immune recognition drives inflammation and produces acute flares; persistent crystal-associated inflammation can result in a chronic arthritis. Definitive identification rests on demonstrating calcium pyrophosphate crystals in synovial fluid, classically rhomboid and weakly positively birefringent under polarised light, distinguishing them from urate crystals. A subset of disease, particularly when it appears young or in an atypical distribution, is associated with underlying metabolic conditions affecting calcium, iron, magnesium or phosphate handling.

Clinical relevance

CPPD disease is an important and common cause of arthritis in older people, overlaps clinically with gout, osteoarthritis and other inflammatory arthritides, and its incidental imaging finding of chondrocalcinosis must be interpreted in context. This entry describes how the disease is conceptualised, classified and diagnosed; it is educational and is not a basis for individual diagnosis or treatment.

Epidemiology

The prevalence of calcium pyrophosphate deposition rises steeply with age, with radiographic chondrocalcinosis becoming common in later decades of life, making CPPD a frequent cause of inflammatory arthritis in the elderly. It is closely associated with osteoarthritis. When CPPD presents at a younger age, is widespread, or is familial, an underlying metabolic disorder — such as haemochromatosis, primary hyperparathyroidism or hypomagnesaemia — is more likely to be relevant.

History

The disease entered modern rheumatology in the early 1960s, when calcium pyrophosphate crystals were identified in the synovial fluid of patients whose acute attacks mimicked gout, giving rise to the term "pseudogout". Over subsequent decades the broader spectrum — from asymptomatic chondrocalcinosis to chronic arthritis — and the links to ageing, osteoarthritis and metabolic disease were characterised. European recommendations later standardised the terminology, establishing calcium pyrophosphate deposition (CPPD) disease and its clinical subforms and clarifying its diagnosis and management.

Debates

How should CPPD be classified and named?

A standardised scheme distinguishes chondrocalcinosis, acute CPP crystal arthritis and chronic CPP crystal inflammatory arthritis, replacing older overlapping labels; how these forms relate to one another and to osteoarthritis continues to be refined.

How strong is the relationship between CPPD and osteoarthritis?

Calcium pyrophosphate deposition and osteoarthritis frequently coexist, and whether and how each contributes to the other's development is debated, complicating both classification and interpretation of imaging findings.

Seminal works

• mccarty-1962
• rosenthal-ryan-2016
• zhang-2011-cppd-1

Frequently asked questions

What is the difference between chondrocalcinosis and CPPD disease?

Chondrocalcinosis is the imaging finding of calcium pyrophosphate crystal deposition in cartilage, which can be asymptomatic, whereas CPPD disease is the broader clinical entity that includes asymptomatic chondrocalcinosis as well as the symptomatic acute and chronic arthritis forms.

When should an underlying metabolic cause be considered in CPPD?

Secondary causes such as haemochromatosis, primary hyperparathyroidism or hypomagnesaemia are more likely to be relevant when CPPD appears at a younger age, is unusually widespread, or runs in families, prompting evaluation for an associated metabolic disorder.