Review Question - QID 217527

This patient's photo demonstrates the absence of the radius with the presence of the thumb, which is characteristic of Thrombocytopenia-Absent Radius (TAR) Syndrome.

Radial longitudinal deficiency is a spectrum of dysplasia and hypoplasia involving the radial structures of the upper extremity. Radial club hand is a dysplasia where patients have a partial or complete absence of the radius with subsequent deformity characterized by the wrist and forearm being perpendicular. There are several syndromes associated with this deformity including VACTER, VACTERL, Fanconi's Anemia, TAR, and Holt-Oram Syndrome. Most patients with radial club hand will also have an absence of the thumb, with TAR being unique in that most patients will have a thumb present. If radial club hand is identified on physical exam further work up is warranted due to its association with pathology involving other organ systems. Work up should include an echocardiogram, renal ultrasound, and CBC (for evaluation of blood cytopenias). TAR is an autosomal recessive genetic disease characterized by congenital thrombocytopenia and absent radius with a normal thumb. Often the thrombocytopenia resolves over the patient's first year of life. The phenotype of TAR can be quite variable from the near-complete absence of the arm and forearm to isolated absence of the radius.

Goldfarb et al. evaluated thumb function and appearance in 7 TAR patients (14 thumbs). They found that thumbs were relatively normal in length and girth, but were on average wider than normal thumbs. Functionally, the thumbs evaluated all lacked interphalangeal joint active motion, with 32-degree extensor lag of the metacarpophalangeal joints. Tested activities were difficult for patients, especially grasping large objects.

Dr. Lamb published a study in 1977 to review the basic science of radial club hand and the outcomes of 68 patients with 117 radial club hand deformities. He discussed the embryologic involvement of the apical ectodermal ridge in the deformity correction and its association with other congenital anomalies. Included in the study is the progression of surgical options with centralization being considered the best option at the time. He does advise against surgical treatment if limited elbow motion is present, surgery would further shorten the forearm, or if surgery would likely limit the functionality of the extremity.

Maschke et al published an extensive review of radial longitudinal deficiency. They discussed the associated syndromes, embryology of upper extremity development, and anatomic manifestations. They discuss deficiencies of the thumb and forearm, common muscular deficiencies, and vascular and neurologic anomalies.

Figure A is a clinical photograph of a radial club hand with the presence of the thumb which is commonly present in TAR patients.

Incorrect Answers:
Answers 1-3, 5: While all of these disorders are associated with radial club hand, often they have an associated absence of the thumb. Components of each are:
VATER: Vertebral anomalies, Anal atresia, Tracheo-Esophageal fistula, and Renal agenesis.
VACTERL: VACTER + Cardiac abnormalities and Limb deformity
Holt Oram Syndrome: radial club hand with cardiac defects. This is an autosomal dominant condition.
Fanconi's Anemia: Radial club hand and aplastic anemia. It is autosomal recessive and requires bone marrow transplant.