All Diseases

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 grow very large.

Although kidneys usually are the most severely affected organs, polycystic kidney disease can cause cysts to develop in your liver and elsewhere in your body. The disease causes a variety of serious complications.

A common complication of polycystic kidney disease is high blood pressure. Kidney failure is another common problem for people with polycystic kidney disease.

Polycystic kidney disease varies greatly in its severity, and some complications are preventable. Lifestyle changes and medical treatments may help reduce damage to your kidneys from complications, such as high blood pressure.

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 an ultrasound exam.

Infrequent or prolonged menstrual periods, excess hair growth, acne, and obesity can all occur in women with polycystic ovary syndrome. In adolescents, infrequent or absent menstruation may raise suspicion for the condition.

The exact cause of polycystic ovary syndrome is unknown. Early diagnosis and treatment along with weight loss may reduce the risk of long-term complications, such as type 2 diabetes and heart disease.

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 — white blood cells and platelets. These excess cells thicken your blood and cause complications, such as such as a risk of blood clots or bleeding.

Polycythemia vera isn't common. It usually develops slowly, and you may have it for years without noticing signs or symptoms. Often, polycythemia vera is found during a blood test done for some other reason.

Without treatment, polycythemia vera can be life-threatening. However, with proper medical care, many people experience few problems related to this disease. Over time, there's a risk of progressing to more-serious blood cancers, such as myelofibrosis or acute leukemia.

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 gradual buildup of amniotic fluid during the second half of pregnancy. Severe polyhydramnios may cause shortness of breath, preterm labor, or other signs and symptoms.

If you're diagnosed with polyhydramnios, your health care provider will carefully monitor your pregnancy to help prevent complications. Treatment depends on the severity of the condition. Mild polyhydramnios may go away on its own. Severe polyhydramnios may require treatment, such as draining the excess amniotic fluid.

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 of skin.

Polymorphous light eruption occurs most often during spring and early summer when a person's exposure to sunlight increases. Repeat episodes are less likely as the summer progresses, but polymorphous light eruption often recurs each year after the first incident.

Although polymorphous light eruption usually goes away on its own without treatment, medications may be needed to treat severe or persistent cases. Measures to protect the skin from sun exposure or light therapy may help prevent recurring episodes of polymorphous light eruption.

Polymyalgia rheumatica is an inflammatory disorder that causes muscle pain and stiffness. The pain and stiffness often occur in your shoulders, neck, upper arms and hips. Symptoms of polymyalgia rheumatica (pol-ee-my-AL-juh roo-MA-ti-kah) usually begin quickly, within two weeks.

Most people who develop polymyalgia rheumatica are older than 65. It rarely affects people younger than 50.

Anti-inflammatory drugs called corticosteroids improve the symptoms of polymyalgia rheumatica, but these drugs require careful monitoring for serious side effects.

Polymyalgia rheumatica is related to another inflammatory disorder called giant cell arteritis, which can cause headaches, vision difficulties, jaw pain and other symptoms. It's possible to have both of these conditions together.

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 adults in their 30s, 40s or 50s. It's more common in blacks than in whites, and women are affected more often than men. Polymyositis signs and symptoms usually develop gradually, over weeks or months.

While there is no cure for polymyositis, treatment — ranging from medications to physical therapy — can improve your muscle strength and function.

Poor color vision is a reduced ability to distinguish between certain colors. Although many people use the term "colorblind" to refer to the reduced ability to discriminate between colors, true colorblindness is a total lack of color vision, which is rare.

Poor color vision is usually inherited. Men are more likely to be born with poor color vision. Most people with poor color vision can't distinguish between certain shades of red and green. Less commonly, people with poor color vision can't distinguish between shades of blue and yellow.

Certain eye diseases and some medications also can cause poor color vision.

Porphyria (poor-FEAR-e-uh) refers to a group of disorders that result from a buildup of natural chemicals that produce porphyrin in your body. Porphyrins are essential for the function of hemoglobin — a protein in your red blood cells that links to porphyrin, binds iron, and carries oxygen to your organs and tissue. High levels of porphyrins can cause significant problems.

Porphyria mainly affects your nervous system, skin and other organs. The signs and symptoms of porphyria can vary, depending on the specific type and severity. Porphyria is usually inherited — one or both parents pass along an abnormal gene to their child. But in some types of porphyria, environmental factors may trigger the development of symptoms.

Treatment depends on the type of porphyria you have. Although porphyria usually can't be cured, certain lifestyle changes may help you manage it.

Post-concussion syndrome is a complex disorder in which various symptoms — such as headaches and dizziness — last for weeks and sometimes months after the injury that caused the concussion.

Concussion is a mild traumatic brain injury, usually occurring after a blow to the head. Loss of consciousness isn't required for a diagnosis of concussion or post-concussion syndrome. In fact, the risk of post-concussion syndrome doesn't appear to be associated with the severity of the initial injury.

In most people, post-concussion syndrome symptoms occur within the first seven to 10 days and go away within three months, though they can persist for a year or more.

Post-concussion syndrome treatments are aimed at easing specific symptoms.