Conclusion
Holt-Oram syndrome is characterized by:
- Upper-extremity malformations (often more severe on the left side); carpal bone anomalies are always present; radial or thenar bones are usually involved, triphalangeal or absent thumb, radial ray aplasia, phocomelia, abnormal position of the hand.
- Personal/family history of congenital heart diesease (75 % of affected individuals have a congenital heart disease); most commonly: ostium secundum atrial septal defect, ventricular septal defect.
- Cardiac conduction defect; first-degree atrioventricular block which may progress into complete heart block.
Inheritance is autosomal dominant but the majority of cases are the result of
de novo mutations . There is a 50 % chance that the offspring of the individual with Holt-Oram syndrome will be affected as well. There is a 100 % penetrance for the upper extremity anomalies. The severity of defects is increasing in successive generations (anticipation). In such a case, detailed prenatal ultrasound screening aimed at upper extremities and fetal heart is necessary. Molecular genetic testing is available, mutation in TBX5 is present in 70 % of cases of Holt-oram syndrome.
Differential diagnosis
Differential diagnosis includes: Fanconi anemia, Thrombocytopenia-absent radius syndrome (thumbs are always present), VACTERL, Heart-hand syndrome II, III, teratogen exposure (Thalidomide, Valproate) and trisomy 18.