04/09/2026
April brings a new month and a new set of monthly illnesses, diseases, and conditions to bring more awareness to. First this month we are bringing awareness to Thrombocytopenia Absent Radius (TAR) Syndrome.
TAR Syndrome comes from mutations in the RBM8A gene, the gene code for a protein involved in the production of other proteins, resulting in irregular development of certain tissue. It is inherited when both copies of the allele (variant form of a specific gene, located in a particular position on a chromosome, which determines distinct traits) are present, also known as a autosomal recessive pattern.
Every patient will not have the same symptoms, some even causing little to no problems in adulthood. However about 90% of all those affected by TAR Syndrome develop symptoms that are related to low levels of the platelets in the blood during the first year after birth. Platelets are special blood cells that stick together to form clots in order to stop bleeding. In TAR Syndrome megakaryocytes (special cells in the bone marrow) are ineffective or improperly developed (hypoplastic), where as those megakaryocytes would develop into platelets in those without it. Maturation of megakaryocytes does not occur causing low platelet levels (hypomegakaryocytic thrombocytopenia); the exact reason for failing development of megakaryocytes is unfortunately unknown.
Those with TAR Syndrome experience a high and low level of platelets in the blood and episodes are most frequent in the first 2 years of life, however they can be triggered or preceded by things such as viral illness (digestive illnesses in particular), surgery, stress, or even cows milk (as mentioned yesterday). Low levels can result in hemorrhaging (severe bleeding). Frequent nosebleeds, vomiting blood, or bloody stools are all specific symptoms of thrombocytopenia. Patients also may suffer from bleeding within the skin layer/layers (below the mucous membranes) which results in easy bruising and/or pin-point sized reddish/purplish spots on the skin. Severe patients the bleeding episodes, especially in the brain, may lead to deadly complications; some TAR patients with history of brain bleeds have reported intellectual difficulties.
Skeletal abnormalities in TAR Syndrome were discussed yesterday with being categorized with the absence of the radius (bone in your forearm, thumb side), with both arms being affected and thumbs present. The thumbs often distinguish it from other radii involved disorders. The thumbs, fingers, and hands are unaffected almost all the time, though they can be abnormally short. Other skeletal abnormalities can include underdevelopment or absence of the ulna, an undeveloped humerus or shoulder girdle, or in severe cases the hands may be joined to the trunk by irregularly shaped, small bone. Some patients may involve the lower limbs and can range between hardly noticeable to significantly malformed. Those with lower limb abnormalities may exhibit knee abnormalities such as loose kneecaps that slide improperly within its groove and potentially can slide out of socket, bones of the knee fused together, or the absence of a knee cap. Hip dislocation, improper inward rotation of the legs long bones, bowing of the legs, feet and toe abnormalities. Abnormalities of the lower limbs can potentially affect the ability to walk.
https://paleyinstitute.org/tar-syndrome/
https://rarediseases.org/rare-diseases/thrombocytopenia-absent-radius-syndrome/