TAR syndrome

The TAR syndrome (after eng. Thrombocytopenia - Absent Radius Syndrome), and radial aplasia - thrombocytopenia syndrome, is a hereditary malformation syndrome with typically on either side of missing radius ( radius) in existing thumbs, and extra low platelet counts (thrombocytopenia).

The TAR syndrome is very rare, with just over 100 cases. It was first described in 1929 by the Americans HM Greenwald and J. Sherman. In 2007, a microdeletion on chromosome 1 q21.1 locus ( 1q21.1 - deletion syndrome ) has been described as a necessary but not sufficient gene mutation. The autosomal recessive inheritance takes place, with great variability in the individual form. Women are affected slightly more often.

Symptoms

Always there are the following changes:

  • Thrombocytopenia ( low platelet counts ) and thus increased bleeding tendency. The thrombocytopenia is particularly pronounced in the first two years of life and is largely to adulthood back. Operations should be avoided in the first two years. Even later but life-threatening bleeding events are still possible. Especially in the first months of life may lead to intracranial hemorrhage, with a motor or mental retardation as a result.
  • On both sides ( bilateral ) absence of the spoke ( radial aplasia ), while the thumb is always present and has a normal function. This deviation of the hand after radial ( thumb down) with club hand deformity. This also the ulna ( ulna ) is always shortened and bent, in about 20 % it is also missing. Also, the upper arm bone (humerus ) is usually shortened and dysplastic ( malformed ). Elbow, shoulder and wrist are restricted in movement.

Other changes are also made frequently:

  • Leukemia -like changes up to 70 % in the first two years of life, with a greatly increased number of white blood cells (leukocytes ), especially with infections. However, there is no leukemia, it does not require treatment.
  • Frequently cow's milk allergy or intolerance, thereby conditionally frequent diarrhea (diarrhea) and increase of thrombocytopenia and leukocytosis, often with eosinophilia. The symptoms improved also in the course of development and in adults, there is hardly any.
  • With up to 50 % concomitant dysplasia of the lower extremities, especially hip dysplasia, coxa valga, Kniegelenkssubluxation, Patelladysplasie with dislocation, knee stiffening and foot and toe deformities.
  • Most dwarfism
  • About one third heart defects, especially tetralogy of Fallot and atrial septal defect
  • On the eye occasionally ptosis. Glaucoma is also described, but this may cause intraocular hemorrhage.

Differential Diagnosis

Especially in the first months of life with bleeding and thrombocytopenia is to distinguish a Fanconi anemia, otherwise there are similarities with the Holt -Oram syndrome and Roberts syndrome. The Tetraphokomelie thrombocytopenia syndrome has as part of the TAR syndrome, not be considered as an independent disease.

When TAR syndrome is per se no motor development disorder or neurological limitations. The race start is usually at best limited by the lack of Abstützfähigkeit. The mental development is unremarkable in itself, retardations are probably always the result of intracranial bleeding in the first months of life. A supply of prosthetic arms is possible, but rarely useful, since this reduces the residual function is further restricted.

Swell

  • F. Hefti: pediatric orthopedics in practice. Springer -Verlag, Berlin 1997, ISBN 3- 540-61480 -X.
  • B. Leiber: The clinical syndromes. Urban and Schwarzenberg, Munich 1996, ISBN 3-541-01718- X.
  • TAR syndrome in Online Mendelian Inheritance in Man.
Congenital disorder 1q21.1 deletion syndrome Autosome Recessive trait Coxa vara Digital Object Identifier
762048
de