Atrial septal defect, ostium primum type is a congenital heart defect in which there is a hole in the wall (septum) between the two upper chambers (atria) of the heart. This type of defect is caused by a failure of the septum primum to form proper...

Atrial septal defect, ostium secundum type is a congenital heart defect in which there is a hole in the wall (septum) between the two upper chambers (atria) of the heart. This type of atrial septal defect is the most common type, accounting for ab...

Atrial septal defect, sinus venosus type is a type of congenital heart defect in which there is an abnormal opening between the upper chambers of the heart (the atria). This type of defect is usually located in the upper part of the atrial septum,...

Atrial septal defect-atrioventricular conduction defects syndrome (ASD-AVCD) is a rare genetic disorder characterized by a combination of two heart defects: an atrial septal defect (ASD) and an atrioventricular conduction defect (AVCD). An ASD is ...

Atrial septal defects (ASD) are a type of congenital heart defect in which there is a hole in the wall (septum) between the two upper chambers (atria) of the heart. This hole allows oxygen-rich blood from the left atrium to flow into the right atr...

Atrial standstill is a rare cardiac arrhythmia in which the atria of the heart stop beating. This condition can lead to a lack of blood flow to the rest of the body, resulting in dizziness, fainting, and even death. Treatment typically involves th...

Atrichia with papular lesions (APL) is a rare genetic disorder characterized by the absence of scalp hair (atrichia) and the presence of small, raised bumps (papules) on the skin. It is caused by mutations in the FOXL2 gene. Symptoms may include t...

Atrioventricular defect-blepharophimosis-radial and anal defect syndrome (AVBRAD) is a rare genetic disorder characterized by a combination of heart defects, blepharophimosis (a condition in which the eyelids are abnormally narrow), radial and ana...

Atrioventricular septal defect (AVSD) is a congenital heart defect in which there is an abnormal connection between the two upper chambers of the heart (the atria) and the two lower chambers of the heart (the ventricles). This defect can cause blo...

Atrophic lichen planus is a rare form of lichen planus, a chronic inflammatory skin condition. It is characterized by thin, atrophic (thinning) patches of skin that are usually lighter in color than the surrounding skin. The patches may be itchy o...

Atrophoderma vermiculata is a rare skin condition characterized by small, pitted, and slightly raised patches on the skin. It is most commonly found on the face, neck, and upper chest, and is thought to be caused by a combination of genetic and en...

Attention deficit hyperactivity disorder (ADHD) is a mental-health condition that has characteristics of difficulty concentrating, controlling impulses, and/or excessive activity. Though there is no particular cause of ADHD, there a...

Attention deficit hyperactivity disorder is a behavioral condition characterized by distractibility, impulsivity, and/or hyperactivity. Although there is no single cause for ADHD, there are a number of biological and social factors ...

Attention deficit hyperactivity disorder (ADHD) is one of the most common chronic disorders affecting school-age children. Current research indicates prevalence rates of 3% to 5% with males being diagnosed with this disorder two and a half times m...

Attenuated Chediak-Higashi syndrome (A-CHS) is a rare, inherited disorder that affects the immune system. It is caused by a mutation in the CHS1 gene, which is responsible for producing a protein that helps the body fight off infections. People wi...

ATTRV122I amyloidosis is a rare, inherited form of amyloidosis caused by a mutation in the transthyretin (TTR) gene. It is characterized by the buildup of abnormal proteins in the body's organs and tissues, leading to organ damage and other seriou...