105 Thrombocytopenia-Absent Radius Syndrome
TAR syndrome
Bilateral aplasia of radius, thumbs present, thrombo- cytopenia improving with age
Frequency: Rare (more than 100 documented cas- es).
Genetics
Autosomal recessive (OMIM 274000).
Clinical Features
• Normal lifespan if child survives to 2 years
• Malformed upper extremities, radial aplasia with thumbs in place, tetraphocomelia, limited exten- sion of hands, radial deviation
• Mandibular and maxillary hypoplasia
• Congenital heart defect
• Hepatosplenomegaly
• Renal malformations
• Epistaxis, purpura
• Thrombocytopenia (<100,000 platelets/mm
3), leukemoid reaction (1st year)
Differential Diagnosis
• Fanconi anemia
• Holt-Oram syndrome
• Roberts/SC phocomelia syndrome
• Aase syndrome
Radiographic Features Upper Limbs
• Bilateral absence of radii (100%)
• Ulnar hypoplasia (100%), bilateral absence of ulna (20%), unilateral absence of ulna (10%)
• Abnormal (50%) or bilaterally absent (5%) hu- merus
• Thumbs always present
• Hypoplastic digits
• Hypoplastic or fused phalanges
• Carpal bone hypoplasia or fusion
• Hypoplastic or absent middle phalanx of 5th digit Shoulder
• Hypoplastic or absent glenoid fossa, acromion, scapula or clavicle
• Clavicles with lateral hooks
Lower Limbs
• Reduction defects, including fibular hypoplasia and phocomelia
• Joint instability or dislocation (hip, knee, patella)
• Coxa valga
• Genu varum
• Femoral and tibial torsion
• Abnormal tibiofibular joint
• Hypoplastic or absent patella
• Clubfoot
• Abnormal toe position, overriding 5th toe Skull
• Hypoplasia of mandible and maxilla Spine
• Irregularity of the vertebral end-plates
• Minor vertebral anomalies Chest
• Minor rib anomalies
Bibliography
Hall JG. Thrombocytopenia and absent radius (TAR) syn- drome. J Med Genet 1987; 24: 79–83
Hall JG, Levin J, Kuhn JP, Ottenheimer EJ, van Berkum KAP, McKusick VA. Thrombocytopenia with absent radius (TAR). Medicine 1969; 48: 411–39
Lipson AH. Letters to the editors. Radial ray defects and asso- ciated anomalies; unique nature of the radial deficiencies and facial dysmorphism in the TAR syndrome. Clin Genet 1990; 37: 78–80
McLaurin TM, Bukrey CD, Lovett RJ, Mochel DM. Management of thrombocytopenia-absent radius (TAR) syndrome.
J Pediatr Orthop 1999; 19: 289–96
Moir JS, Scotland T. Thrombocytopenia absent radius syn- drome and knee deformity. J Pediatr Orthop B 1995;
4: 222–5
Ray R, Zorn E, Kelly T, Hall JG, Sommer A. Lower limb anom- alies in the thrombocytopenia absent-radius (TAR) syn- drome. Am J Med Genet 1980; 7: 523–8
Schoenecker PL, Cohn AK, Sedgwick WG, Manske PR, Salafsky I, Millar EA. Dysplasia of the knee associated with the syn- drome of thrombocytopenia and absent radius. J Bone Joint Surg Am 1984; 66: 421–7
Urban M, Opitz C, Bommer C, Enders H, Tinschert S, Witkows- ki R. Bilaterally cleft lip, limb defects, and haematological manifestations: Roberts syndrome versus TAR syndrome.
Am J Med Genet 1998; 79: 155–60 Thrombocytopenia-Absent Radius Syndrome
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Fig. 105.2 a, b. Patient 2, newborn.
Note bilaterally absent radii, short ulnas, radial deviation of hands, clavicular lateral hooks, bilateral hip dislocation, and unossified distal femoral and proximal tibial epiphyses. Also note enlarged cal- varium relative to facial bones, and maxillary and mandibular hypoplasia
a b
