Chondrocalcinosis 2 is a rare disease characterized by the accumulation of calcium pyrophosphate dihydrate (CPP) crystals in and around the joints. A buildup of these crystals can lead to joint pain and damage that is progressive (worsens over time). Signs and symptoms of the disease include chronic joint pain or sudden, recurrent episodes of pain, as well as stiffness or swelling of the joints. Chondrocalcinosis 2 is actually a familial form of chondrocalcinosis (also known as calcium pyrophosphate deposition disease or CPPD), which is caused by a similar buildup of CPP crystals but is associated with the aging process. The age-related chondrocalcinosis is quite common, whereas chondrocalcinosis 2 is not. In addition, people with chondrocalcinosis 2 are more likely to have symptoms that develop earlier in adulthood than the age-related form..

Chondrocalcinosis 2 is caused by changes in the ANKHgene. The disease is inherited in an autosomal dominant manner. Chondrocalcinosis 2 is diagnosed based on imaging such as X-rays. The diagnosis can be confirmed with genetic testing of the ANKH gene. Treatment may include the use of corticosteroids, pain relievers, and physical therapy.

ANKH gene. When a genetic change causes a disease, it is also known as a pathogenic variation. The ANKH gene provides instructions to make a protein that may interact with or regulate other proteins involved in the controlling the formation of calcium pyrophosphate (CPP) mineralization. Mineralization is the process by which calcium and phosphorus form crystals to become part of the bone structure. Although the exact function of the ANKH protein is not known, it is known that the pathogenic variation in the ANKH gene allows too many CPP crystals to build up in the cartilage of joints. The buildup of crystals weakens the cartilage and causes it to break down more easily, leading to the joint pain and other symptoms associated with chondrocalcinosis 2.

ANKH gene in each cell of the body. Most genes, including the ANKH gene, come in pairs, and a person inherits one copy of each gene from their mother and the other from their father.

When a person with chondrocalcinosis 2 has children, each child has a:

• 50% chance to inherit the changed copy of ANKH, meaning they may develop chondrocalcinosis 2
• 50% chance to inherit the working copy of ANKH, meaning they will not develop chondrocalcinosis 2

In some cases, a person with chondrocalcinosis 2 inherits the disease from an affected parent. In other cases, the pathogenic variation that causes the disease is new (de novo) in the affected person, and there is no history of the disease in the family. However, a person with a new pathogenic variation in the ANKH gene has a 50% chance of passing this disease-causing change on to each of his or her children.

The symptoms can be chronic (occurring all the time) or may occur in sudden episodes. If the pain occurs in episodes, it can last anywhere from several hours to several weeks. In some cases, episodes of pain may cause fevers. The attack may affect only one joint or multiple joints. Joints that are most commonly affected include the knees, wrists, hips, or shoulders. Some people with chondrocalcinosis 2 may experience pain in the back if calcium deposits develop around the bones of the spine.

If a doctor suspects that a person has chondrocalcinosis caused by a change (pathogenic variation) in the ANKH gene, genetic testing may be ordered to confirm the diagnosis and identify other family members who may have the same pathogenic variation.

• Joint aspiration (draining of fluid from the affected joint)
• Corticosteroid injections
• Non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin or ibuprofen

For people who have frequent episodes of pain or for whom other medications are not effective, small doses of a medication called colchicine may be recommended. However, this medication has side effects and may not help everyone with chondrocalcinosis 2.

In some cases, people with chondrocalcinosis 2 may be required to wear a splint or brace to prevent too much movement. In other cases, physical therapy may be recommended for safe movement of the affected joint.

For some people with chondrocalcinosis 2, medications and other therapies work well to treat signs and symptoms of the disease. For others, the buildup of calcium pyrophosphate dehydrate (CPP) crystals is severe and can cause pain that is not relieved with treatment. At this time there is, unfortunately, no way to prevent or remove the buildup of CPP crystals in the joints. In some cases, the pain associated with chondrocalcinosis 2 can be severe and very disabling.