What is Aicardi-Goutieres syndrome (AGS)?

Aicardi-Goutieres syndrome (AGS) is a form of inherited encephalopathy that affects newborn infants and results in severe mental and physical handicap. There are two forms of the syndrome: a severe early-onset form, and a late-onset form that has less impact upon neurological functions. The early-onset form affects about 20 percent of all babies who have AGS. These infants are born with neurological and liver abnormalities, such as enlargement of the liver and spleen, and elevated liver enzymes. Their jittery behavior and poor feeding ability mimic congenital viral infection.

Babies with later-onset AGS begin having symptoms after the first weeks or months of normal development, which appear as a progressive decline in head growth, weak or stiffened muscles (spasticity), and moderate to severe mental and developmental retardation. Symptoms last for several months, and include irritability, inconsolable crying, intermittent fever, seizures, and loss of developmental skills. Children may also have puffy swelling on the fingers, toes, and ears that resemble chilblains. Several children exhibit a noticeable startled reaction to sudden noise. For babies with the later-onset form, as symptoms lessen, there is no further worsening of the disease.

AGS is difficult to diagnose, since many of the symptoms are similar to those of other disorders. Diagnosis is made on the clinical symptoms of the disease, as well as the characteristic brain abnormalities seen in an MRI brain scan. Cerebrospinal fluid (CSF), taken using a "spinal tap," can be tested for increased levels of a specific immune system cell (lymphocyte), which indicates a condition known as chronic lymphocytosis. Since these cells are elevated only during infection, lymphocytosis without infection can act as an indicator of AGS. CSF may also be tested for elevated levels of interferon-gamma, which supports the diagnosis of AGS.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.