What are the signs and symptoms of Andersen-Tawil syndrome? Anderson-Tawil syndrome causes episodes of muscle weakness (periodic paralysis), changes in heart rhythm (arrhythmia), and developmental abnormalities. The most common changes affecting the heart are ventricular arrhythmia, which is a disruption in the rhythm of the heart's lower chambers, and long QT syndrome. Long QT syndrome is a heart condition that causes the heart muscle to take longer than usual to recharge between beats. If untreated, the irregular heartbeats can lead to discomfort, fainting, or cardiac arrest. Physical abnormalities associated with Andersen-Tawil syndrome typically affect the head, face, and limbs. These features often include a very small lower jaw (micrognathia), dental abnormalities, low-set ears, widely spaced eyes, and unusual curving of the fingers or toes (clinodactyly). Some affected people also have short stature and an abnormal curvature of the spine (scoliosis). The Human Phenotype Ontology provides the following list of signs and symptoms for Andersen-Tawil 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) Specific learning disability 7.5% Antegonial notching of mandible - Autosomal dominant inheritance - Bidirectional ventricular ectopy - Blepharophimosis - Brachydactyly syndrome - Broad forehead - Bulbous nose - Cleft palate - Clinodactyly of the 5th finger - Clinodactyly of the 5th toe - Delayed eruption of permanent teeth - Delayed skeletal maturation - Facial asymmetry - Growth abnormality - High palate - Hypertelorism - Hypoplasia of dental enamel - Hypoplasia of the maxilla - Joint laxity - Low-set ears - Malar flattening - Microcephaly - Oligodontia - Palpitations - Periodic hypokalemic paresis - Persistence of primary teeth - Preauricular pit - Prolonged QT interval - Prominent frontal sinuses - Scapular winging - Scoliosis - Short foot - Short mandibular rami - Short metacarpal - Short metatarsal - Short palm - Short palpebral fissure - Short phalanx of finger - Slender long bone - Small hand - Syncope - Toe syndactyly - Triangular face - 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.