Omenn syndrome is a genetic disease that results in problems with the immune system, a part of the body that protects against substances and organisms that can cause human disease. Another name for the syndrome is reticuoendotheliosis with eosinophilia. It is often classified as a subtype of severe combined immunodeficiency (SCID), and is inherited in an autosomal recessive fashion, meaning that both parents must pass on a mutated gene in order for one of their offspring to be affected. Symptoms include a skin rash, enlarged lymph nodes, and intestinal problems. Treatment of the disease often involves a bone marrow stem cell transplant and immunosuppressive medications.
A number of different gene mutations can cause Omenn syndrome. When the disease was first identified, it was thought that mutations in recombination-activating genes 1 and 2 (RAG-1 and RAG-2) were the only causes of the disease. Later research showed that different mutations in other genes can also cause the syndrome. In order for an individual to have Omenn syndrome, he or she must inherit abnormal genes from both parents.
The mutations causing Omenn syndrome cause problems with producing enough of the white blood cells, including the T cells and B cells, that play a critical role in the body's defenses. Additionally, sometimes the white blood cells produced act abnormally and attack elements of the person's own body, including the lining of the intestines and the skin. Patients therefore have problems due to both an underactive immune system, making them susceptible to different infections, as well as problems due to an overactive immune system, as cells of the body attack their own organs.
Symptoms of Omenn syndrome typically become evident shortly after birth. Many affected individuals experience a red scaly skin rash, enlarged lymph nodes, and diarrhea. These symptoms are similar to those seen with graft-versus-host disease, which is a condition that can be seen in some patients who receive organ transplants. Often patients also have an enlarged liver and spleen, a condition known as hepatosplenomegaly. Patients are susceptible to a number of bacterial infections, and often have symptoms as a result, including fever, breathing problems, and skin lesions.
In order to make the diagnosis of Omenn syndrome, it is important to perform a panel of different laboratory tests because a number of different diseases could cause similar symptoms. Patients typically have elevated levels of white blood cells in their blood, and in particular have high levels of a type called eosinophils. They also have an elevated amount of immunoglobulin type E in their blood, which is a type of protein produced by white blood cells used to fight infections. In some cases a patient’s genes can be analyzed to check for the presence of known mutations that could cause the syndrome.
Treatment of Omenn syndrome can be complicated. It is often best left to a specialist trained in treating immune disorders. One of the mainstays of treatment is bone marrow stem cell transplantation, a procedure that attempts to replace the part of the body that makes the white blood cells. Often this is combined with immunosuppressive drugs, which can protect the body from attacking itself. Patients are also monitored for infection, and treated with antibiotics if any symptoms become evident.