Hyper-IgD Syndrome is a rare genetic condition characterized by elevated levels of immunoglobulin D (IgD) in the blood. It is often associated with recurrent fevers, joint pain, and abdominal discomfort. The syndrome is caused by mutations in the mevalonate kinase gene, which plays a role in the body's immune response. Individuals with Hyper-IgD Syndrome may experience periodic fever episodes, typically lasting a few days. These episodes can be triggered by infections or stress. Diagnosis is usually confirmed through blood tests that measure IgD levels and genetic testing to identify mutations in the mevalonate kinase gene.