TAR Syndrome
Thrombocytopenia Absent Radius (TAR) Syndrome is characterized by the absence of a bone called the radius in each forearm and a deficiency of blood cells involved in the blood-clotting process. It is a rare genetic disorder that occurs in less than 1 in 100,000 live births. The first year is often the hardest due to internal bleeding which contributes to a mortality rate of about 30-40%. In some cases, serious hemorrhaging episodes may lead to an intellectual disability. After the first two years most individuals go on to have a normal life expectancy.
Cause
Mutations in the RBM8A gene cause TAR syndrome. The RBM8A gene provides instructions for making a protein called RNA-binding motif protein 8A. This protein is believed to be involved in several important cellular functions involving the production of other proteins.
TAR syndrome is a rare disorder, affecting fewer than 1 in 100,000 newborns.
Frequency
Other features that can occur in TAR syndrome include malformations of the heart or kidneys. Some people with this disorder have unusual facial features including a small lower jaw (micrognathia), a prominent forehead, and low-set ears. About half of affected individuals have allergic reactions to cow's milk that may worsen the thrombocytopenia associated with this disorder.