Health A to Z

Authoritative, patient-focused summaries of key ailments and diseases

Patient Basics: Abdominal Aortic Aneurysm

Originally published by Harvard Health. What Is It? An abdominal aortic aneurysm is an abnormal swelling in the aorta. It can be fatal.The aorta is the...

Patient Basics: Absence Seizures (Petit Mal Seizures)

Originally published by Harvard Health. What Is It? The brain's nerve cells (neurons) communicate by firing tiny electric signals. During a seizure (convulsion), the firing pattern...

Patient Basics: Ankle Fracture

Originally published by Harvard Health. What Is It? When a bone breaks or cracks, the injury is called a fracture. In the ankle, three different bones...

Patient Basics: Ankylosing Spondylitis

Originally published by Harvard Health. What Is It? Ankylosing spondylitis is a form of arthritis that mainly affects the lower back. It causes inflammation and damage...

Patient Basics: Anorexia Nervosa

Originally published by Harvard Health. What Is It? Anorexia nervosa is an eating disorder that affects about 1 in 100-200 girls or women in the United...

Patient Basics: Ankle Sprain

Originally published by Harvard Health. What Is It? An ankle sprain is a stretch or tear in one or more of the ankle ligaments. Ankle ligaments...

Patient Basics: Antibiotic-Associated Diarrhea

Originally published by Harvard Health. What Is It? In healthy people, many different species of bacteria live inside the bowel. Many are harmless or even helpful...

Patient Basics: Antiphospholipid Antibody Syndrome (APS)

Originally published by Harvard Health. What Is It? Antiphospholipid antibody syndrome (APS) is a condition defined by the presence of abnormal antibodies and a tendency to...

Patient Basics: Antisocial Personality Disorder

Originally published by Harvard Health. What Is It? Antisocial personality disorder, like other personality disorders, is a longstanding pattern of behavior and experience that impairs functioning...

Patient Basics: Aplastic Anemia

Originally published by Harvard Health. What Is It? Aplastic anemia is a rare, potentially fatal disease in which the bone marrow doesn't make enough blood cells....
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