What are the signs and symptoms of Holt-Oram syndrome? People with Holt-Oram syndrome have abnormally developed bones in their upper limbs. At least one abnormality in the bones of the wrist (carpal bones) is present. Additional bone abnormalities may also be present, such as a missing thumb, a long thumb that looks like a finger, partial or complete absence of bones in the forearm, an underdeveloped bone of the upper arm, and abnormalities of the collar bone or shoulder blades. About 75% of affected people have heart problems, which can be life-threatening. The most common problems are an atrial septal defect (ASD) and a ventricular septal defect (VSD). Some people 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 uncoordinated contraction of the heart muscle (fibrillation). The features of Holt-Oram syndrome are similar to those of a condition called Duane-radial ray syndrome but these two disorders are caused by mutations in different genes. The Human Phenotype Ontology provides the following list of signs and symptoms for Holt-Oram syndrome. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormality of the wrist 90% Abnormality of the metacarpal bones 50% Aplasia/Hypoplasia of the radius 50% Aplasia/Hypoplasia of the thumb 50% Arrhythmia 50% Atria septal defect 50% Triphalangeal thumb 50% Ventricular septal defect 50% Hypoplasia of the radius 37.8% Phocomelia 11% Abnormality of the aorta 7.5% Abnormality of the humerus 7.5% Abnormality of the ribs 7.5% Abnormality of the shoulder 7.5% Abnormality of the sternum 7.5% Anomalous pulmonary venous return 7.5% Aplasia of the pectoralis major muscle 7.5% Complete atrioventricular canal defect 7.5% Finger syndactyly 7.5% Hypoplastic left heart 7.5% Patent ductus arteriosus 7.5% Pectus excavatum 7.5% Radioulnar synostosis 7.5% Scoliosis 7.5% Sprengel anomaly 7.5% Thoracic scoliosis 7.5% Abnormality of the carpal bones - Abnormality of the vertebrae - Absent thumb - Autosomal dominant inheritance - Partial duplication of thumb phalanx - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.