TAR syndrome (thrombocytopenia with absent radius) is a rare genetic disorder that is characterized by the absence of the radius bone in the forearm and a dramatically reduced platelet count.[1] It is associated with cardiac defects, dysmorphic features, and petechiae. It involves a 1q21 deletion with RMB8A variant on other allele.
Absence of the radius bone in the forearm with preservation of the thumb[citation needed].
Other common links between people with TAR syndrome include anemia, heart problems, kidney problems, knee joint problems, and frequently milk allergy. Different cases with leukemia in patients with TAR are described in.[clarification needed][3]
This condition requires mutations in both chromosomes[clarification needed].[4] The first mutation is inheritance of a 1q21.1 deletion and the second is in the remaining in the RBM8A gene.
Approximately 95% of TAR patients have one non-functional copy of the RBM8A gene.[5][6]
Treatment
Treatments range from platelet transfusions[1] to surgery aimed at either centralizing the hand over the ulna to improve functionality of the hand or aimed at 'normalizing' the appearance of the arm, which is much shorter and 'clubbed'.[citation needed] There is some controversy surrounding the role of surgery[citation needed]. The infant mortality rate has been curbed by new technology, including platelet transfusions, which can even be performed in utero[citation needed]. The critical period is the first and sometimes second year of life[citation needed]. For most people with TAR, platelet counts improve as they grow out of childhood.[citation needed]
Epidemiology
The incidence is 0.42 per 100,000 live births[citation needed].
History
In 1929 Greenwald and Sherman(( described the first patient with TAR Syndrome.[7] 40 years later Hall collected 40 cases and introduced the name "Thrombocytopenia with absent radius".[8] In 1988 Hedberg published an article with 100 cases.[9]
References
^ abToriello HV (December 2016). "Thrombocytopenia Absent Radius Syndrome.". In Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJ, Stephens K, Amemiya A, Toriello HV (eds.). GeneReviews [Internet]. University of Washington, Seattle. PMID20301781.
^Brodie SA, Rodriguez-Aulet JP, Giri N, Dai J, Steinberg M, Waterfall JP, Roberson D, Ballew BJ, Zhou W, Anzick SL, Jiang Y, Wang Y, Zhu YJ, Meltzer PS, Boland J, Alter BP, Savage SA (2019) 1q21.1 deletion and a rare functional polymorphism in siblings with thrombocytopenia-absent radius-like phenotypes. Cold Spring Harb Mol Case Stud 5(6)
^Hedberg VA, Lipton JM (1988). "Thrombocytopenia with absent radii. A review of 100 cases". review. The American Journal of Pediatric Hematology/Oncology. 10 (1): 51–64. doi:10.1097/00043426-198821000-00010. PMID3056062.
Further reading
Goldfarb CA, Wall L, Manske PR (September 2006). "Radial longitudinal deficiency: the incidence of associated medical and musculoskeletal conditions". primary. The Journal of Hand Surgery. 31 (7): 1176–82. doi:10.1016/j.jhsa.2006.05.012. PMID16945723.
