Definition of Hyper-IgD syndrome

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Hyper-IgD syndrome: A genetic disorder characterized by recurring attacks of chills and fever that usually start before the first birthday and last for 4 to 6 days, usually accompanied by swollen glands in the neck and abdominal pain with vomiting or diarrhea. Other symptoms may include headache, joint pain (arthralgia), arthritis of the large joints, and reddish spots (macules) and bumps (papules) on the skin, and bleeding (petechiae and purpura) into the skin. The attacks can be triggered by minor trauma, surgery, vaccination or stress. Patients may be free of attacks for months or even years.

The key laboratory abnormality is a continuously high level of IgD (immunoglobulin D). By "high" is meant more than 100 IU (International Units) per milliliter of blood. Over 80% of patients also have high IgA (immunoglobulin A) levels.

The syndrome is an autosomal recessive trait. The gene for the syndrome is on chromosome 12. It encodes the enzyme mevalonate kinase. Most patients are compound heterozygotes with two different mutations in the gene for mevalonate kinase, one mutation inherited from one parent, and the other mutation from the other parent.