Holt–Oram Syndrome

Abstract

Holt–Oram syndrome (HOS) is characterized by the combination of upper limb anomalies, in particular of the radial ray, and congenital heart defects. Abnormalities of the thumbs – aplasia, hypoplasia, or triphalangeal thumb – are the most common finding, often associated with hypoplastic thenar, limited supination of the forearm, or both. Other common findings are reduced digit length, clinodactyly of the 5th finger, and hypoplasia of individual fingers, most commonly involving the index and middle fingers. Hypoplasia of the radius occurs in approximately 50 %, and aplasia of the radius is present in approximately 25 %. Ulnar hypoplasia occurs only in individuals with radial defects. In the most severe cases, the defect extends up to the humerus, resulting in upper extremity phocomelia. Carpal bones may be abnormal, including bipartite scaphoid. Narrow, sloping shoulders are common, accompanied by mildly hypoplastic clavicles, hypoplasia/aplasia of the pectoralis major muscle, and pectus excavatum or carinatum. Limb defects are always bilateral and often asymmetrical, with the left side being more severely affected. Vertebral anomalies and thoracic scoliosis are further skeletal abnormalities.