DEFINITION Polycystic kidney disease (PKD) is an inherited disorder in which clusters of cysts develop primarily within your kidneys. Cysts are noncancerous round sacs containing water-like fluid. The cysts vary in size and, as they accumulate more fluid, they can…
DEFINITION Polio is a contagious viral illness that in its most severe form causes paralysis, difficulty breathing and sometimes death. In the U.S., the last case of naturally occurring polio happened in 1979. Today, despite a concerted global eradication campaign,…
DEFINITION Penicillin allergy is an abnormal reaction of your immune system to the antibiotic drug penicillin. Penicillin is prescribed for treating various bacterial infections. Common signs and symptoms of penicillin allergy include hives, rash and itching. Severe reactions include anaphylaxis,…
DEFINITION Periodontitis (per-e-o-don-TIE-tis) is a serious gum infection that damages the soft tissue and destroys the bone that supports your teeth. Periodontitis can cause tooth loss or worse, an increased risk of heart attack or stroke and other serious health…
DEFINITION Peripheral artery disease (also called peripheral arterial disease) is a common circulatory problem in which narrowed arteries reduce blood flow to your limbs. When you develop peripheral artery disease (PAD), your extremities — usually your legs — don’t receive…
DEFINITION Your peripheral nerves link your brain and spinal cord to the other parts of your body, such as your muscles and skin. Peripheral nerves are fragile and easily damaged. A nerve injury can interfere with your brain’s ability to…
DEFINITION Peripheral nerve tumors are masses that occur on or near the network of nerves (peripheral nerves) that link the brain and spinal cord to other parts of the body. Peripheral nerve tumors may occur anywhere in the body and…
DEFINITION A personality disorder is a type of mental disorder in which you have a rigid and unhealthy pattern of thinking, functioning and behaving. A person with a personality disorder has trouble perceiving and relating to situations and to people.…
DEFINITION Pet allergy is an allergic reaction to proteins found in an animal’s skin cells, saliva or urine. Signs of pet allergy include those common to hay fever, such as sneezing and runny nose. Some people may also experience signs…
DEFINITION Peyronie’s (pay-roe-NEEZ) disease is the development of fibrous scar tissue inside the penis that causes curved, painful erections. Men’s penises vary in shape and size. Having a curved erection is common and isn’t necessarily a cause for concern. However,…
DEFINITION Phantom pain is pain that feels like it’s coming from a body part that’s no longer there. Doctors once believed this post-amputation phenomenon was a psychological problem, but experts now recognize that these real sensations originate in the spinal…
DEFINITION A pheochromocytoma (fee-o-kroe-moe-sy-TOE-muh) is a rare, usually noncancerous (benign) tumor that develops in cells in the center of an adrenal gland. You have two adrenal glands, one above each kidney. Your adrenal glands produce hormones that give instructions to…