DEFINITION Pinworm infection is the most common type of intestinal worm infection in the United States and one of the most common worldwide. Pinworms are thin and white, measuring about 1/4 to 1/2 inch (about 5 to 13 millimeters) in…
DEFINITION A pilonidal (pie-low-NIE-dul) cyst is an abnormal pocket in the skin that usually contains hair and skin debris. A pilonidal cyst is almost always located near the tailbone at the top of the cleft of the buttocks. These cysts…
DEFINITION Pneumonitis (noo-moe-NIE-tis) is a general term that refers to inflammation of lung tissue. Although pneumonia is technically a type of pneumonitis because the infection causes inflammation, most doctors are referring to other causes of lung inflammation when they use…
DEFINITION POEMS syndrome is a rare blood disorder that damages your nerves and affects many other parts of the body. POEMS stands for these signs and symptoms: Polyneuropathy.Numbness, tingling and weakness in your legs — and over time,…
DEFINITION A popliteal artery aneurysm is an abnormal bulge that occurs in the wall of the artery that runs through the area behind your knee joint. CAUSES SYMPTOMS
DEFINITION Polymyositis (pol-e-my-o-SY-tis) is an uncommon inflammatory disease that causes muscle weakness affecting both sides of your body. Polymyositis can make it difficult to climb stairs, rise from a seated position, lift objects or reach overhead. Polymyositis most commonly affects…
DEFINITION Polymorphous light eruption, also known as polymorphic light eruption, is an itchy rash caused by sun exposure in people who have developed a sensitivity to sunlight (photosensitivity). The rash usually appears as red, tiny bumps or slightly raised patches…
DEFINITION Polyhydramnios (pol-e-hy-DRAM-nee-os) is the excessive accumulation of amniotic fluid — the fluid that surrounds the baby in the uterus during pregnancy. Polyhydramnios occurs in about 1 percent of pregnancies. Most cases of polyhydramnios are mild and result from a…
DEFINITION Polycythemia vera (pol-e-sigh-THEE-me-uh VEER-uh) is a slow-growing type of blood cancer in which your bone marrow makes too many red blood cells. Polycythemia vera may also result in production of too many of the other types of blood cells…
DEFINITION Polycystic ovary syndrome (PCOS) is a common endocrine system disorder among women of reproductive age. Women with PCOS may have enlarged ovaries that contain small collections of fluid — called follicles — located in each ovary as seen during…
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,…