Diagnostic Considerations
Fanconi anemia
The manifestations of TAR and Fanconi anemia frequently overlap. The following features may help to differentiate the two conditions:
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In Fanconi anemia, thrombocytopenia is rarely present at birth; it develops later on in childhood or even in adulthood
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Radial defects are seen in only 30% of patients with Fanconi anemia; when present, such defects are usually associated with absent thumb, unlike in TAR, where radial defects are the sine qua non and the thumb is usually present, even though it could be abnormal
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Chromosome fragility is a diagnostic feature of Fanconi anemia; TAR patients should probably be tested for this to exclude Fanconi anemia
ARTUS
Amegakaryocytic thrombocytopenia with radioulnar synostosis (ARTUS) is usually associated with a HOXA11 gene mutation, a condition of autosomal dominant inheritance. [20, 21] The thrombocytopenia persists and does not improve with age. Furthermore, aplastic anemia may develop later in life.
RAPADILINO syndrome
RAPADILINO syndrome is a rare syndrome characterized by radial hypoplasia or aplasia, patellar hypoplasia or aplasia, cleft or highly arched palate, diarrhea, dislocated joints, small size (>2 standard deviations below the mean in height), limb malformation, slender nose, and normal intelligence.
Roberts syndrome
Roberts syndrome is characterized by prenatal and postnatal growth retardation; craniofacial anomalies, especially facial clefts; limb deficiencies, including tetraphocomelia in most patients; and genital hyperplasia. Parental consanguinity rate is high.
Thalidomide embryopathy
Thalidomide embryopathy is the teratogenic effect of thalidomide when the drug is taken during pregnancy. Affected infants can have limb and digit defects, craniofacial anomalies, hearing and vision defects, and improper formation of organs including the heart and kidneys.
Trisomy 18 (Edward syndrome)
Patients with trisomy 18 may have craniofacial anomalies (eg, prominent occiput, short palpebral fissures, micrognathia, external ear variations); digit anomalies (eg, clenched fist with the index finger overlapping the third finger, the fifth finger overlapping the fourth, hypoplastic nails, thumb aplasia); short sternum (breastbone); rocker-bottom feet; and cardiac, pulmonary, GI, and genitourinary defects.This conditon is frequently associated with thrombocytopenia. However patients also exhibit esophageal dysplasia.
VACTERL association
This is a syndrome of congenital anomalies that includes vertebral dysgenesis, anal atresia with or without fistula, cardiac defects (ventricular septal defect [VSD]), tracheoesophageal fistula, and renal and limb anomalies.
Differential Diagnoses
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Infant with thrombocytopenia-absent radius syndrome. The arms and forearms are shortened, with radial deviation of both hands because of the absence of bilateral radii. The legs are normal. See also Media files 2 and 3.
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Same infant as in Media files 1 and 3. Close-up photograph of arm and forearm (volar aspect). Note the petechiae.
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Same infant as in Media files 1 and 2. Close-up photograph of arm and forearm (dorsal aspect).
