TAR is an acronym that stands for
Thrombocytopenia, Absent Radius. This is a rare
condition that is most severe in the neonatal period and early infancy and
which is associated with thrombocytopenia and bilateral radial aplasia. It
was first described in 1951. An autosomal recessive inheritance disorder
that presents with abnormalities in skeletal, gastrointestinal, hematologic,
and cardiac systems. Pancytopenia similar to Fanconi. The major cause of
mortality is hemorrhage. The incidence of hemorrhage is limited to the first
14 months of life.
The frequency is 0.42 cases per 100,000 live births in
Spain. Male:female ratio is equal. This medical condition is very rare in
the United States.
Unknown. It is suggested that the “TAR gene”
probably exerts its effect between gestation weeks 4 and 8 because this
would explain the association of limb deformity and congenital heart disease
found in this syndrome.
Finding of bilateral absence of the radius and
Skeletal anomalies in addition to absent radii
include ulnar hypoplasia, humeral hypoplasia, shoulder girdle hypoplasia,
various hand anomalies, and lower limb dysplasias. Mandibular and maxillary
hypoplasia are occasional findings. Congenital cardiac disease occurs in
30% of patients, most commonly tetralogy of Fallot and atrial septal
defect. Additional findings may include hepatosplenomegaly and renal
abnormalities. Symptomatic thrombocytopenia occurs in 50% of patients by
the age of 1 week, although it may not occur until early adult life.
Purpura, petechiae, epistaxis, gastrointestinal hemorrhage, and hematuria are common modes
of presentation. Patients presenting outside the neonatal period may give a
history of easy bruising. Thrombocytopenia may be episodic and is commonly
precipitated by infection. In those patients surviving to adult life, the
thrombocytopenia tends to be less severe and may be asymptomatic. Laboratory
investigations may reveal a normal or low platelet count and eosinophilia.
During episodes of thrombocytopenia, a leukocytosis with left shift is
common. Anemia is usually secondary to blood loss rather than marrow
aplasia. Megakaryocytes are not seen on examination of the bone marrow. The
thrombocytopenia has been treated by steroids and splenectomy.
Careful assessment of airway for
maxillary/mandibular hypoplasia. Cardiovascular assessment: examine for
evidence of cardiac disease; consider ECG and echocardiography. Cardiac
catheterization as indicated by proposed procedure and cardiac status.
Laboratory investigations: full blood cell count, electrolytes, urea, and
creatinine. Correct anemia secondary to blood loss; administer platelets
preoperatively in presence of ongoing hemorrhage or if the platelet count
is less than 50,000/mm3.
Presence of cardiac disease may dictate
specific technique, risk of paradoxical air embolism should be considered in
all these patients. Intravenous access may be difficult because of limb
malformation, and central venous cannulation may be difficult because of
shoulder girdle hypoplasia. The radial artery is usually present but may be
abnormally positioned if intraarterial pressure monitoring is indicated.
Ensure platelets are available for the perioperative period. Regional
anesthesia is relatively contraindicated even in the ...