Diseases & Conditions
The human body is a remarkable structure. It's designed to efficiently manage the wear and tear of everyday life and fend off all sorts of threats. Most of us are healthy for most of our lives. But we're also susceptible to hundreds of injuries, diseases, and conditions. Some are quite common, others are extremely rare. Here are some of the most common conditions that affect humans.
Diseases & Conditions Articles
Amyotrophic lateral sclerosis (ALS) causes a slow degeneration of nerve cells that control muscle movements. As a result, people with ALS gradually lose the ability to control their muscles. Fortunately, their capacity to think and remember things usually is not affected. ALS is also known as Lou Gehrig's disease, after the famous U.S. baseball player who developed the disease.
Your gallbladder stores bile until you eat, then releases bile into your small intestine to help digest food. Bile is made in the liver. It contains a mix of products such as bilirubin, cholesterol, and bile acids and salts. Bile ducts are drainage "pipes" that carry bile from the liver to the gallbladder and from the gallbladder to the small intestine.
A variety of diseases can affect your bile ducts. All block the bile ducts in some way, which is why the various diseases cause similar symptoms.
Gallstones are the most common cause of blocked bile ducts. Stones typically form inside the gallbladder and can block the common bile duct, the drainpipe at the base of the liver. If the duct remains blocked, bilirubin backs up and enters the blood stream. If bacteria above the blockage accumulates and backs up into the liver, it may cause a severe infection called ascending cholangitis. If a gallstone stops in between the gallbladder and the common bile duct, an infection called cholecystitis may occur.
Less common causes of blockages include cancers of the bile duct (cholangiocarcinomas) and strictures (scars that narrow the ducts after infection, surgery or inflammation).
Other bile duct diseases are uncommon, and include primary sclerosing cholangitis and primary biliary cirrhosis. Typically diagnosed in mid-adulthood, these conditions create ongoing inflammation in the bile duct walls, which can narrow and scar the walls. Primary sclerosing cholangitis is more common in people with inflammatory bowel disease (ulcerative colitis or Crohn's disease). Primary biliary cirrhosis is more common in women. It is sometimes associated with autoimmune diseases such as Sjögren's syndrome, thyroiditis, scleroderma or rheumatoid arthritis.
Biliary atresia is a rare form of bile duct blockage that occurs in some infants two weeks to six weeks after birth, a time when the bile ducts have not completed their development normally.
The chronic conditions of primary sclerosing cholangitis, primary biliary cirrhosis and biliary atresia can result in inflammation and scarring of the liver, a condition known as cirrhosis.
Decompression sickness, also called generalized barotrauma or the bends, refers to injuries caused by a rapid decrease in the pressure that surrounds you, of either air or water. It occurs most commonly in scuba or deep-sea divers, although it also can occur during high-altitude or unpressurized air travel. However, decompression sickness is rare in pressurized aircraft, such as those used for commercial flights.
When you scuba dive with compressed air, you take in extra oxygen and nitrogen. Your body uses the oxygen, but the nitrogen is dissolved into your blood, where it remains during your dive. As you swim back toward the surface after a deep dive, the water pressure around you decreases. If this transition occurs too quickly, the nitrogen does not have time to clear from your blood. Instead, it separates out of your blood and forms bubbles in your tissues or blood. It is these nitrogen bubbles that cause decompression sickness. The condition is called the bends because joint pain, a common symptom, can double you over.
What happens inside your body during decompression sickness is similar to what happens when you open a carbonated drink. When you open the can or bottle, you decrease the pressure surrounding the beverage in the container, which causes the gas to come out of the liquid in the form of bubbles. If nitrogen bubbles form in your blood, they can damage blood vessels and block normal blood flow.
Factors that put you at higher risk of decompression sickness include:
Heart muscle birth defects, including patent foramen ovale, atrial septal defect and ventricular septal defect
Being older than 30
Low cardiovascular fitness
High percentage of body fat
Use of alcohol or tobacco
Fatigue, seasickness or lack of sleep
Injuries (old or current)
Diving in cold water
Someone with an abnormal hole or opening in the heart from a birth defect is at especially high risk of developing serious symptoms from decompression illness. Because bubbles create high blood pressure in the lungs, blood and bubbles from your veins may flow more readily through the heart's opening. This means your blood can re-circulate into arteries without first getting oxygen. An opening in the heart can also allow a relatively large air bubble (called an air embolism) to circulate into your arteries. An air embolism can cause a stroke.
People with asthma or another lung disease may have thin-walled air pockets in their lungs called bullae. These pockets do not empty quickly when the persons exhales. As they return to the surface after a deep dive, air in the bullae may expand. If a bulla ruptures, it could cause a collapsed lung or allow a large air bubble (air embolism) to enter the arteries.
Edema is swelling of both legs from a buildup of extra fluid. Edema has many possible causes:
Prolonged standing or sitting, especially in hot weather, can cause excess fluid to accumulate in the feet, ankles and lower legs.
Tiny valves inside the veins of the legs can become weakened, causing a common problem called venous insufficiency. This problem makes it more difficult for the veins to pump blood back to the heart, and leads to varicose veins and buildup of fluid.
Severe chronic (long-term) lung diseases, including emphysema and chronic bronchitis, increase pressure in the blood vessels that lead from the heart to the lungs. This pressure backs up in the heart. The higher pressure causes swelling in the legs and feet.
Congestive heart failure, a condition in which the heart can no longer pump efficiently, causes fluid buildup in the lungs and other parts of the body. Swelling is often most visible in the feet and ankles.
Pregnancy can cause edema in the legs as the uterus puts pressure on the vena cava, a major blood vessel that returns blood to the heart from the legs. Fluid retention during pregnancy also can be caused by a more serious condition called preeclampsia.
Low protein levels in the blood caused by malnutrition, kidney and liver disease can cause edema. The proteins help to hold salt and water inside the blood vessels so fluid does not leak out into the tissues. If a blood protein, called albumin, gets too low, fluid is retained and edema occurs, especially in the feet, ankles and lower legs.
Hair loss can range from mild hair thinning to total baldness. Hair can fall out for many different reasons. Medically, hair loss falls into several categories, including:
Telogen effluvium — This common form of hair loss happens two to three months after a major body stress, such as a prolonged illness, major surgery or serious infection. It also can happen after a sudden change in hormone levels, especially in women after childbirth. Moderate amounts of hair fall out from all parts of the scalp, and may be noticed on a pillow, in the tub or on a hairbrush. While hair on some parts of the scalp may appear thinner, it is rare to see large bald spots.
Drug side effects — Hair loss can be a side effect of certain medications, including lithium, beta-blockers, warfarin, heparin, amphetamines and levodopa (Atamet, Larodopa, Sinemet). In addition, many medications used in cancer chemotherapy — such as doxorubicin (Adriamycin) — commonly cause sudden hair loss affecting the entire head.
Symptom of a medical illness — Hair loss can be one of the symptoms of a medical illness, such as systemic lupus erythematosus (lupus), syphilis, a thyroid disorder (such as hypothyroidism or hyperthyroidism), a sex-hormone imbalance or a serious nutritional problem, especially a deficiency of protein, iron, zinc or biotin. These deficiencies are most common in people on restrictive diets and women who have very heavy menstrual flow.
Tinea capitis (fungal infection of the scalp) — This form of patchy hair loss happens when certain types of fungi infect the scalp. This causes the hair to break off at the scalp surface and the scalp to flake or become scaly. Tinea capitis is a common form of patchy hair loss in children.
Alopecia areata — This is an autoimmune disease that causes hair to fall out in one or more small patches. The cause of this condition is unknown, although it is more common in people who have other autoimmune diseases. When the same process causes total loss of hair from the scalp it is known as alopecia totalis.
Traumatic alopecia — This form of hair loss is caused by hairdressing techniques that pull the hair (tight braiding or cornrowing), expose hair to extreme heat and twisting (curling iron or hot rollers) or damage the hair with strong chemicals (bleaching, hair coloring, permanent waves). In addition, some people have an uncommon psychiatric disorder (trichotillomania) in which compulsive hair pulling and twisting can cause bald spots.
Hereditary pattern baldness, or androgenetic alopecia — In men, hair loss may follow the typical male pattern (receding front hairline and/or thinning hair at the top of the head). This is the most common type of hair loss, and it can begin at any time in a man's life, even during his teen years. It usually is caused by the interaction of three factors: an inherited tendency toward baldness, male hormones and increasing age. Many women will develop some degree of female-pattern baldness. In women, thinning occurs over the entire top or crown of the scalp, sparing the front of the scalp.
Hyperkeratosis is a thickening of the outer layer of the skin. This outer layer contains a tough, protective protein called keratin.
This skin thickening is often part of the skin's normal protection against rubbing, pressure and other forms of local irritation. It causes calluses and corns on hands and feet. It can cause whitish areas inside the mouth.
Other forms of hyperkeratosis can occur as part of the skin's defense against:
Chronic (long-lasting) inflammation
Radiation of sunlight
Less often, hyperkeratosis develops on skin that has not been irritated. These types of hyperkeratosis may be part of an inherited condition. They may begin soon after birth and can affect skin on large areas of the body.
There are many examples of hyperkeratosis. They include:
Corns and calluses. Corns and calluses develop in areas of skin exposed to repeated friction or pressure. In response, thick layers of dead skin cells pile up and harden.
Corns usually develop on irritated toes. Calluses form on the soles of the feet and the palms of the hands.
For many people, corns and calluses are simply a cosmetic nuisance. But for others, they are a painful and troublesome medical problem.
Warts. Warts are small bumps on the skin that are caused by human papilloma virus (HPV) infection. Plantar warts grow on the soles of the feet.
HPV usually is spread by direct contact. It is typically spread by touching or shaking hands with someone who already has a wart. It may also be spread by coming in contact with a contaminated surface. For example, by walking barefoot on a gym floor or a pool deck or by wearing someone else's shoes.
Chronic eczema. Eczema is an inflammation of the skin. It can be triggered by allergies, irritating chemicals and other factors. Eczema is also called dermatitis.
Eczema causes itching, redness and tiny blisters. When the inflammation is difficult to control, chronic eczema can lead to:
Changes in skin color
Localized hair loss
Lichen planus. This condition may appear as a lacy white patch on the inside of the mouth. Or it may be an itchy, violet, scaly patch elsewhere on the skin. Lichen planus may be related to an abnormal reaction of the immune system.
Actinic keratoses. These are flat, red, rough, sandpaper-like spots or patches of skin. They can be as tiny as a few millimeters.
They are caused by excessive exposure to the ultraviolet radiation of sunlight. They occur on sun-exposed areas of skin. And they have the potential to develop into skin cancer.
Seborrheic keratoses. These are small, noncancerous skin growths. They can be tan, brown or black. They appear on the face, trunk, arms or legs. Seborrheic hyperkeratoses are very common. Their cause is a mystery.
Inherited conditions. Several inherited conditions cause hyperkeratosis. They cause a widespread, thick, platelike scaling of the skin. Symptoms begin either shortly after birth or during early childhood.
Infectious mononucleosis is an illness caused by a viral infection. It is commonly called mononucleosis, or "mono." Mononucleosis is most often caused by the Epstein-Barr virus. In some cases, it is caused by other viruses.
Mononucleosis has been nicknamed the "kissing disease." This is because Epstein-Barr virus commonly is transmitted during kissing. However, sneezes and coughs also can transmit the virus.
Mononucleosis typically occurs the first time a person is infected with Epstein-Barr virus. But infection with Epstein-Barr virus does not always cause mononucleosis. It often causes only a mild illness or no illness at all.
Plague is caused by Yersinia pestis bacteria. It can be a life threatening infection if not treated promptly. Plague has caused several major epidemics in Europe and Asia over the last 2,000 years. Plague has most famously been called "the Black Death" because it can cause skin sores that form black scabs. A plague epidemic in the 14th century killed more than one-third of the population of Europe within a few years. In some cities, up to 75% of the population died within days, with fever and swollen skin sores.
Sickle cell anemia is an inherited blood disorder.
Chronic destruction of red blood cells
Episodes of intense pain
Vulnerability to infections
In some cases, early death
Hemoglobin is a protein in red blood cells that carries oxygen. People with sickle cell anemia inherit a defective type of hemoglobin. When oxygen levels inside a red blood cell get low, the defective hemoglobin forms long rods. These rods stretch the red blood cells into long, abnormal "sickle" shapes. In contrast, normal red blood cells are disc-shaped.
Toenail fungus is a condition that disfigures and sometimes destroys the nail. It is also called onychomycosis
Toenail fungus can be caused by several different types of fungi. Fungi are microscopic organisms related to mold and mildew.
These fungi thrive in the dark, moist and stuffy environment inside shoes. As they grow, fungi feed on keratin. Keratin is the protein that makes up the hard surface of the toenails.
Factors that increase the risk of developing toenail fungus include:
Wearing tight-fitting shoes or tight hosiery
Practicing poor foot hygiene
Wearing layers of toenail polish, which doesn't allow the nail to breathe
Being a military personnel, athlete or miner. This is because toenail fungi may spread from foot to foot on the floors of showers and locker rooms.
Having a chronic illnesses, such as diabetes or HIV
Having a circulatory problem that decreases blood flow to the toes
However, many people with toenail fungus have no clear risk factors.
Toenails on the big toe and little toe are the most likely to develop a toenail fungus. This may be partly because the big toe and little toe are constantly exposed to friction from the sides of shoes.