Radial dysplasia

Radial dysplasia
Other names	Radial longitudinal deficiency
Radial club hand with thumb missing (ectrodactyly)

Radial dysplasia, also known as radial club hand or radial longitudinal deficiency, is a congenital difference occurring in a longitudinal direction resulting in radial deviation of the wrist and shortening of the forearm. It can occur in different ways, from a minor anomaly to complete absence of the radius, radial side of the carpal bones and thumb.^[1] Hypoplasia of the distal humerus may be present as well and can lead to stiffness of the elbow.^[2] Radial deviation of the wrist is caused by lack of support to the carpus, radial deviation may be reinforced if forearm muscles are functioning poorly or have abnormal insertions.^[3] Although radial longitudinal deficiency is often bilateral, the extent of involvement is most often asymmetric.^[1]

The incidence is between 1:30,000 and 1:100,000 and it is more often a sporadic mutation rather than an inherited condition.^[1][3] It is one of the possible co occurring birth defects of the embryonic mesoderm within VACTERL association. In case of an inherited condition, several syndromes are known for an association with radial dysplasia, such as the cardiovascular Holt–Oram syndrome and the hematologic Fanconi anemia and TAR syndrome.^[1]Other possible causes are an injury to the apical ectodermal ridge during upper limb development,^[2] intrauterine compression, or maternal drug use (thalidomide).^[3]