Holt-Oram Syndrome
What is Holt-Oram Syndrome?
Holt-Oram syndrome is a disorder that affects bones in the arms and hands (the upper limbs) and may also cause heart problems. All people with this disorder have at least one limb abnormality that affects bones in the wrist (carpal bones). Often, these wrist bone abnormalities can be detected only by X-ray. Affected individuals may have additional bone abnormalities that can include a missing thumb or a thumb that looks like a finger, partial or complete absence of bones in the forearm, an underdeveloped bone of the upper arm, and abnormalities that affect the collar bone and shoulder blades. Bone abnormalities may affect each arm differently, and in these cases the left side is usually affected more than the right side. Sometimes, only one arm and/or hand (on either the right side or the left side) is affected.
About 75 percent of individuals with Holt-Oram syndrome have heart problems. The most common problem is a defect in the muscular wall, or septum, that separates the right and left sides of the heart. Atrial septal defects (ASD) are caused by a hole in the septum between the left and right upper chambers of the heart (atria), and ventricular septal defects (VSD) are caused by a hole in the septum between the left and right lower chambers of the heart (ventricles). Sometimes people with Holt-Oram syndrome have cardiac conduction disease, which is caused by abnormalities in the electrical system that coordinates contractions of the heart chambers. Cardiac conduction disease can lead to problems such as a slower-than-normal heart rate (bradycardia) or a rapid and ineffective contraction of the heart muscles (fibrillation). Cardiac conduction disease can occur along with other heart defects (such as septal defects) or as the only heart problem in people with Holt-Oram syndrome.
**taken from Genetics Home Reference pages
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