Atypical genitalia, formerly known as ambiguous genitalia, is a rare disorder in which your newborn’s external genitals aren’t clearly defined. Your infant may not have the typical genitals of a male or a female. Your infant’s genitals may not have developed completely, or they may have features of both sexes. Infants with atypical (intersex) genitals may have external genitals that …

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, slow-growing tumor that develops in your jaw. Ameloblastomas grow from the same type of cell that forms your tooth enamel. About 80% of the time, it develops in your lower jaw in the space behind your back teeth (molars). Ameloblastomas are benign (noncancerous). But ameloblastomas aren’t benign in the way most people may think of the word, as in harmless. They can grow …

Amenorrhea is when you don’t get your menstrual period. There are two kinds of amenorrhea: primary and secondary. Primary amenorrhea is when a person older than 15 has never gotten their first period. Secondary amenorrhea happens when a person doesn’t get a period for more than three months. How does menstruation work? A complex system of hormones controls your menstrual cycle. Every …

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 and aggressive (fast-growing) cancer that forms inside the ampulla of Vater. The ampulla of Vater is the opening where the ducts that carry digestive juices from your pancreas and liver meet. These juices combine in the ampulla of Vater before draining into the first part of your small intestine (duodenum). As ampullary cancer forms so close to your liver, pancreas and other digestive system organs, it …

Amyloidosis is a rare disorder that happens when proteins in your body change or mutate, becoming twisted clumps of misshapen proteins that gather on your organs and tissues. Amyloidosis can be widespread (systemic) or localized to one area. Systemic is the most common form of amyloidosis, affecting organs and multiple tissues. In some instances, systemic amyloidosis may cause life-threatening organ …