Calcium Pyrophosphate Deposition Disease

Calcium pyrophosphate deposition (CPPD) disease is a crystal deposition arthropathy that affects the cartilage, synovial, and periarticular tissues and is the third most common form of inflammatory arthritis. CPPD disease manifests in various clinical presentations, which often overlap with other types of arthritides. The crystals involved in CPPD disease are composed of calcium pyrophosphate dihydrate and commonly affect larger, weight-bearing joints, including the hips, knees, and shoulders. In some cases, calcium pyrophosphate (CPP) crystal deposits may be visible on imaging without any associated symptoms. Due to its diverse presentation, CPPD is frequently misdiagnosed as other rheumatic conditions, including gout, rheumatoid arthritis, polymyalgia rheumatica, or even ankylosing spondylitis. The European Alliance of Associations for Rheumatology (EULAR) categorizes CPPD into 4 categories: (1) asymptomatic CPPD; (2) osteoarthritis with CPPD; (3) acute CPP crystal arthritis/pseudogout; (4) chronic CPP inflammatory crystal arthritis. Other rare types have been noted, including pseudo-polymyalgia rheumatica (pseudo-PMR), pseudo-neuropathic arthropathy, and tumoral CPPD. Briefly, the various types of CPPD present as follows: Asymptomatic CPPD: This form may present asisolated hyaline or fibrocartilage calcifications (chondrocalcinosis) observed on plain x-ray or as osteoarthritis with CPP crystals without classic acute CPPD episodes. Osteoarthritis with CPPD: Many patients with CPPD also have degenerative arthritis, characterized by an unusual distribution similar to osteoarthritis, typically involving the knees, wrists, metacarpophalangeal joints, hips, shoulders, and ankles. This type can present with a gradual onset of pain and slow progressive joint destruction. Acute CPP crystal arthritis/pseudogout: Approximately 25% of patients present with the classic pseudogout presentation, characterized by acute, intermittent, and severe episodes of joint pain and swelling, accompanied by redness and tenderness similar to those of gout. Acute phase reactants may be elevated. Chronic CPP inflammatory crystal arthritis (previously referred to as pseudo-rheumatoid arthritis): This subtype affects approximately 25% of patients with CPPD. Presentation can involve chronic, symmetrical, deforming polyarthritis. The wrists and metacarpal joints are commonly affected, and patients may also develop carpal tunnel syndrome, synovial thickening, localised edema, and flexion contractures of the hands and wrists. Pseudo-polymyalgia rheumatica: Older patients with early morning stiffness and bilateral shoulder pain similar to polymyalgia rheumatica should also be considered for an atypical presentation of CPP arthritis. Involvement of proximal joints may be a feature of CPPD and has been reported in the literature. Pseudo-neuropathic arthropathy: Rarely, patients can present with severe destructive monoarthritis with evidence of joint destruction on radiographic imaging. Tumoral CPPD: This type is characterized by the accumulation of calcium foci and chondroid metaplasia, resulting in a radiographic appearance similar to a tumor. .