Hyper-IgD syndrome

Hyperimmunoglobulinemia D syndrome (HIDS) is a rare genetic condition that causes recurring episodes of elevated body temperature (fevers) from infancy through childhood that tend to become less frequent in adulthood. The fevers usually last 3 to 6 days and may occur spontaneously or in response to stress or vaccinations. During fevers, individuals may have mouth sores, abdominal pain, joint pain, headache, rashes, and nausea. Children with the disorder typically may not reach developmental milestones at the expected time (developmental delays). Other features may include problems with movement and balance (ataxia), eye problems, seizures, and a high number of immune system proteins that help fight infections (immunoglobulins) in the blood. Some affected people may have protein deposits in the kidney (amyloidosis) that may cause kidney damage.

HIDS is caused by changes (mutations) in the MVK gene, which provides instructions for the body to make an enzyme called mevalonate kinase. This enzyme is involved with making cholesterol, a substance that is important for many functions in the body. Mutations in the MVK gene cause the body to decrease production of the enzyme (mevalonate kinase enzyme deficiency) and, in turn, not produce enough cholesterol. HIDS is inherited in an autosomal recessive way, meaning a child needs a mutation in both of their MVK gene copies to have the condition. HIDS is the less severe form of mevalonate kinase enzyme deficiency. Another condition, known as mevalonic aciduria (MVA), is the more severe form of mevalonate kinase enzyme deficiency and is discussed in a separate entry.

There are currently no specific treatments for MVA, but there are some medications that can help symptoms during fevers. If your child has been diagnosed with HIDS, talk with their doctor about ways to manage symptoms. Support groups can provide additional information and connect you with others affected by HIDS.