An anxiety disorder is a type of mental health condition. If you have an anxiety disorder, you may respond to certain things and situations with fear and dread. You may also experience physical signs of anxiety, such as a pounding heart and sweating. It’s normal to have some anxiety. You may feel anxious or nervous if you have to tackle a …

Atypical genitalia, previously known as ambiguous genitalia, is a rare condition in which a newborn’s external sex organs do not appear clearly male or female. In some infants, the genitals may be underdeveloped, appear different from typical male or female anatomy, or show features of more than one sex. The appearance of the external genitals may not match the internal …

Lazy eye (amblyopia) is reduced vision in one eye caused by abnormal visual development early in life. The weaker — or lazy — eye often wanders inward or outward. Amblyopia generally develops from birth up to age 7 years. It is the leading cause of decreased vision among children. Rarely, lazy eye affects both eyes. Early diagnosis and treatment can …

Ameloblastoma is a rare, noncancerous tumor that most commonly develops in the jaw, usually near the molars. It begins in the cells involved in forming the enamel that protects teeth. Although benign, ameloblastoma can be locally aggressive and grow into the surrounding jawbone. The most common form tends to grow slowly but can become quite large if not treated. As …

Amenorrhea is the absence of menstruation and is commonly defined as missing one or more menstrual periods. It is not a disease itself but a sign of an underlying condition, natural body process, or hormonal change. There are two main types of amenorrhea. Primary amenorrhea occurs when a person has not started menstruating by age 15. This form is often …

Chagas disease (also called American trypanosomiasis) is an illness you get from infection with a parasite. The parasite is spread by triatomine bugs (“kissing bugs”), mostly in Mexico and Central and South America. The thing about Chagas is that most people don’t know they’re infected. Many people don’t have any symptoms in the initial (acute) phase. But without treatment, most people …

Amnesia is when you have serious memory loss. It can be a symptom of other conditions or happen by itself. Amnesia comes from ancient Greek and means, “forgetfulness.” But it’s more than that. Forgetfulness is misplacing your keys or not remembering to do something while running errands. Amnesia involves being unable to remember significant events or details from your life. …

Transient global amnesia (TGA) is a rare medical condition in which you experience a sudden episode of memory loss. During a TGA episode, you can’t form new memories (a condition called anterograde amnesia), and you have difficulty recalling recent memories (a condition called retrograde amnesia). “Transient” means passing. Transient global amnesia episodes usually last no more than several hours. In rare cases, they …

Ampullary cancer is a rare type of cancer that begins in the ampulla of Vater. The ampulla of Vater is a small opening where the bile duct and pancreatic duct join and empty into the small intestine. This location places ampullary cancer close to several important digestive organs, including the liver, pancreas and small intestine. Because of where it starts, …

Amyloidosis is a rare disease that develops when an abnormal protein called amyloid builds up in organs and tissues. This buildup interferes with normal organ function and can lead to serious health problems. Amyloid deposits may affect one organ or multiple organs throughout the body. Organs commonly affected by amyloidosis include the heart, kidneys, liver, spleen, nervous system, digestive tract, …