Thrombocytopenia-Absent Radius Syndrome (TAR)

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Disease Ontology 12 DOID:14699 OMIM 56 274000 KEGG 36 H01847 MeSH 43 C536940 D013921 D038062 NCIt 49 C99038 SNOMED-CT 67 85589009 ICD10 32 Q87.2

ICD10 via Orphanet 33 Q87.2 UMLS via Orphanet 72 C0175703 Orphanet 58 ORPHA3320 MedGen 41 C0175703 SNOMED-CT via HPO 68 111266001 119250001 11934000 127962001 128602000 128613002 13649004 157265008 15911003 16026008 165397008 22066006 224958001 228156007 22841008 237836003 246545002 247578003 248942000 249684000 249769001 249773003 249785006 249808002 253273004 253366007 253549006 253930002 258211005 263029007 268251006 271737000 299236004 299331007 302215000 30288003 31258000 313307000 32958008 34048007 362970003 36760000 37373007 396351009 397932003 405752007 415116008 41729002 443710002 445124008 50563003 59494005 60700002 63567004 64217002 64779008 67531005 70142008 708670007 72535009 7305005 84757009 86299006 86708008 87979003 91138005 91175000 more UMLS 71 C0175703

Genetics Home Reference : ²⁵ Thrombocytopenia-absent radius (TAR) syndrome is characterized by the absence of a bone called the radius in each forearm and a shortage (deficiency) of blood cell fragments involved in clotting (platelets). This platelet deficiency (thrombocytopenia) usually appears during infancy and becomes less severe over time; in some cases the platelet levels become normal. Thrombocytopenia prevents normal blood clotting, resulting in easy bruising and frequent nosebleeds. Potentially life-threatening episodes of severe bleeding (hemorrhages) may occur in the brain and other organs, especially during the first year of life. Hemorrhages can damage the brain and lead to intellectual disability. Affected children who survive this period and do not have damaging hemorrhages in the brain usually have a normal life expectancy and normal intellectual development. The severity of skeletal problems in TAR syndrome varies among affected individuals. The radius, which is the bone on the thumb side of the forearm, is almost always missing in both arms. The other bone in the forearm, which is called the ulna, is sometimes underdeveloped or absent in one or both arms. TAR syndrome is unusual among similar malformations in that affected individuals have thumbs, while people with other conditions involving an absent radius typically do not. However, there may be other abnormalities of the hands, such as webbed or fused fingers (syndactyly) or curved pinky fingers (fifth finger clinodactyly). Some people with TAR syndrome also have skeletal abnormalities affecting the upper arms, legs, or hip sockets. 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.

MalaCards based summary : Thrombocytopenia-Absent Radius Syndrome, also known as tar syndrome, is related to chromosome 1q21.1 deletion syndrome, 1.35-mb and amegakaryocytic thrombocytopenia, congenital. An important gene associated with Thrombocytopenia-Absent Radius Syndrome is RBM8A (RNA Binding Motif Protein 8A), and among its related pathways/superpathways are RNA transport and mRNA surveillance pathway. Affiliated tissues include bone, kidney and brain, and related phenotypes are thrombocytopenia and abnormality of coagulation

NIH Rare Diseases : ⁵² TAR syndrome is characterized by the absence of a bone called the radius in each forearm, short stature , and thrombocytopenia . The thrombocytopenia often appears first in infancy but becomes less severe or returns to normal over time. Infants and young children are particularly vulnerable to episodes of severe bleeding which may occur in the brain and other organs . Children who survive this period and do not have damaging bleeding in the brain usually have a normal life expectancy and normal intellectual development. Other signs and symptoms vary but may include heart defects, kidney defects, and other skeletal abnormalities. About half of people with TAR syndrome also have difficulty digesting cow's milk. TAR syndrome is thought be caused by a deletion of genes on chromosome 1q21.1 in concert with another genetic change that has yet to be identified. Click here to see a diagram of chromosome 1.

OMIM : ⁵⁶ The thrombocytopenia-absent radius syndrome (TAR) is characterized by reduction in the number of platelets and absence of the radius; preservation of the thumb distinguishes TAR from other syndromes that combine blood abnormalities with absence of the radius, such as Fanconi anemia (see 227650). Individuals with TAR have low numbers of megakaryocytes, platelet precursor cells that reside in bone marrow, and frequently present with bleeding episodes in the first year of life that diminish in frequency and severity with age. The severity of skeletal anomalies varies from absence of radii to virtual absence of upper limbs, with or without lower limb defects such as malformations of the hip and knee (summary by Albers et al., 2012). (274000)

KEGG : ³⁶ Thrombocytopenia-absent radius (TAR) syndrome is a rare autosomal recessive syndrome characterized by severe thrombocytopenia and bilateral defects in development of the radii at birth but with preservation of the thumb. Other physical abnormalities have been reported such as ulnar and humeral deformities, rib and cervical anomalies, cardiac lesions (usually septal defects), gastrointestinal and genitourinary abnormalities. Cow's milk allergy is highly prevalent in patients with TAR syndrome. TAR syndrome is caused by the compound (bi-allelic) inheritance of one of two noncoding single-nucleotide variants and a null allele in RBM8A. Clinical management is based on presentation, with platelet transfusions as required for thrombocytopenia and orthopedic intervention for functional optimization of upper limbs.

UniProtKB/Swiss-Prot : ⁷³ Thrombocytopenia-absent radius syndrome: An autosomal recessive disorder characterized by bilateral absence of the radii with the presence of both thumbs, thrombocytopenia, low numbers of megakaryocytes, and bleeding episodes in the first year of life. Thrombocytopenic episodes decrease with age. Skeletal anomalies range from absence of radii to virtual absence of upper limbs, with or without lower limb defects such as malformations of the hip and knee.

Wikipedia : ⁷⁴ TAR syndrome (thrombocytopenia with absent radius) is a rare genetic disorder that is characterized by... more...

GeneReviews: NBK23758

Clinical features from OMIM:

274000

Search NIH Clinical Center for Thrombocytopenia-Absent Radius Syndrome

Search GEO for disease gene expression data for Thrombocytopenia-Absent Radius Syndrome.