Calcium pyrophosphate deposition disease, commonly abbreviated as CPPD and often called pseudogout, is a joint condition caused by the buildup of calcium pyrophosphate crystals in the cartilage of joints. These crystals form deposits inside the joint cartilage and can trigger inflammation, leading to symptoms that closely resemble gout, such as sudden, painful swelling and redness in the affected joint. The knee is one of the most commonly involved joints, but CPPD can affect other joints as well.
The disease occurs when calcium pyrophosphate crystals accumulate in the cartilage, which is the smooth tissue that covers the ends of bones in a joint. Over time, these crystals can cause irritation and inflammation of the joint lining, resulting in episodes of joint pain, swelling, and stiffness. These flare-ups can come on suddenly and may last for days or weeks. Unlike gout, which involves uric acid crystals, CPPD involves calcium pyrophosphate crystals, and the two conditions require different treatments.
On X-rays, CPPD is often identified by the presence of thin, linear or punctate calcifications within the cartilage, especially in areas like the meniscus of the knee or the articular cartilage. These calcifications appear as white lines or spots inside the joint space. Chronic CPPD can lead to joint damage and arthritis, sometimes mimicking osteoarthritis but with distinct features due to the crystal deposits.
The exact cause of CPPD is not always clear, but it is more common in older adults and can be associated with other medical conditions such as joint trauma, metabolic disorders like hyperparathyroidism, or genetic factors. The crystals themselves form when there is an imbalance in the metabolism of calcium and phosphate in the joint fluid.
Symptoms of CPPD can vary widely. Some people may have no symptoms despite having crystal deposits visible on X-rays, while others experience acute attacks of joint inflammation that resemble gout attacks. These attacks typically involve sudden onset of joint pain, swelling, warmth, and redness. The knee is the most frequently affected joint, but wrists, shoulders, ankles, and other joints can also be involved.
Diagnosis of CPPD involves a combination of clinical evaluation, imaging studies like X-rays, and sometimes joint fluid analysis. During an acute flare, a doctor may extract fluid from the affected joint and examine it under a microscope to identify calcium pyrophosphate crystals, which confirms the diagnosis.
Treatment focuses on managing symptoms and preventing flare-ups. Since CPPD causes inflammation, anti-inflammatory medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, or colchicine are commonly used to reduce pain and swelling during attacks. In chronic cases, treatment may also involve physical therapy to maintain joint function and mobility. Unlike gout, lowering uric acid levels is not relevant in CPPD.
CPPD can sometimes be confused with other causes of joint pain and calcifications seen on X-rays, such as osteoarthritis with calcifications, gout, or other rare conditions like synovial chondromatosis or tumoral calcinosis. However, the pattern of calcifications and clinical presentation help doctors differentiate CPPD from these other disorders.
In summary, calcium pyrophosphate deposition disease is a joint disorder caused by calcium pyrophosphate crystal deposits in cartilage, leading to inflammation and arthritis-like symptoms. It is especially common in older adults and can cause sudden painful joint attacks similar to gout but requires different treatment approaches focused on controlling inflammation and preserving joint health.