Scientists identify genetic cause of previously undefined primary immune deficiency disease

Researchers at the National Institutes of Health have identified a genetic mutation that accounts for a perplexing condition found in people with an inherited immunodeficiency. The disorder, called combined immunodeficiency, is characterized by a constellation of severe health problems, including persistent bacterial and viral skin infections, severe eczema, acute allergies and asthma, and cancer.

The team that made the discovery was led by Helen Su, M.D., Ph.D., at the National Institute of Allergy and Infectious Diseases (NIAID), and included collaborators from NIAID and the National Cancer Institute (NCI). The research is reported in this week's New England Journal of Medicine.

"NIH clinicians have cared for people with unusual and difficult-to-treat immune disorders for decades," says NIAID Director Anthony S. Fauci, M.D. "This study exemplifies their commitment to improving the lives of people with these diseases by trying to uncover the causes of these disorders and thereby better understanding how to treat them."

Combined immunodeficiency is a type of primary immune deficiency disease (PIDD) in which several parts of the immune system are affected. This inherited disorder is characterized by increased susceptibility to bacterial, viral and fungal infections of various organs of the body. In some cases, susceptibility to cancers also may be seen.

There are 150 known PIDDs. Approximately 500,000 people in the United States have been diagnosed with a PIDD, while many more remain undiagnosed.

The NIAID and NCI investigators recognized that certain patients with an undefined form of combined immunodeficiency shared enough clinical features to make it likely that the cause might be a common genetic mutation. Originally, these individuals were thought to have a variant form of hyper-immunoglobulinema E syndrome (HIES), a disorder characterized by increased levels of a class of antibodies known as immunoglobulin E, superficial and systemic bacterial and fungal infections, and atopic dermatitis, also known as eczema.

This newly described group, however, had far more severe eczema than is typical in people with variant HIES. They also had extensive and difficult-to-manage viral infections of the skin, such as warts, molluscum contagiosum—a type of poxvirus that only infects the skin—and herpes simplex. Some in this group also developed skin cancers, as well as lymphoma of the skin.

"Even though these individuals were diagnosed with a more uncommon form of HIES, they were still considered to have a mystery disease, because they had severe allergies and had developed cancers," says Dr. Su.

Using a technique called comparative genomic hybridization, a process by which large amounts of DNA is fixed to a computer chip and analyzed for changes in the genes, scientists examined the genes in the tissue samples from five different groups: the 11 individuals with the unknown immunodeficiencies, people with the variant form of HIES, people with classic HIES, those with other immunological diseases, and healthy individuals.