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
Malignant hyperthermia is a severe reaction to a dose of anesthetics. The reaction is sometimes fatal. It is caused by a rare, inherited muscle abnormality. Infrequently, extreme exercise or heat stroke can trigger malignant hyperthermia in someone with the muscle abnormality.
In people with the muscle abnormality, muscle cells have an abnormal protein on their surfaces. The protein does not affect muscle function significantly. That is, until the muscles are exposed to a drug that can trigger a reaction.
When a person with this condition is exposed to one of these drugs:
Calcium stored in muscle cells is released
The muscles contract and stiffen at the same time
There is a dramatic and dangerous increase in body temperature (hyperthermia)
Malignant hyperthermia usually occurs during or after surgery. But it can occur wherever anesthetic medications are used. This includes:
Intensive care units
Symptoms of malignant hyperthermia usually occur within the first hour after exposure to the trigger medication. However, the symptoms can be delayed for up to 12 hours.
Most cases occur in children and adults younger than 30.
A subdural hematoma occurs when a blood vessel near the surface of the brain bursts. Blood builds up between the brain and the brain's tough outer lining. The condition is also called a subdural hemorrhage.
In a subdural hematoma, blood collects immediately beneath the dura mater. The dura mater is the outermost layer of the meninges. The meninges is the three-layer protective covering of the brain.
A subdural hematoma is a life-threatening problem because it can compress the brain.
Most subdural hemorrhages results from trauma to the head. The trauma damages tiny veins within the meninges.
In young, healthy people, bleeding usually is triggered by a significant impact. This type of impact might occur in a high-speed motor vehicle accident.
In contrast, older people may bleed after only a minor trauma. For example, it might happen from falling out of a chair.
A subdural hematoma is also more common in people:
Taking medications that thin the blood
Who abuse alcohol
Who have seizures
An acute subdural hemorrhage is bleeding that develops shortly after a serious blow to the head. Blood accumulates rapidly, causing pressure to rise within the brain. This can result in loss of consciousness, paralysis or death.
When bleeding develops slowly, it is known as a chronic subdural hemorrhage. Bleeding may develop over a period of weeks to months
This form of bleeding is much more common in older people. The head trauma that causes chronic subdural hemorrhage is often minor. Many of those affected cannot recall a head injury.
Tay-Sachs disease is an inherited disease caused by an abnormal gene. People with this abnormal gene do not have an important enzyme called hexosaminidase A (HEXA) that helps to break down a fatty material called ganglioside GM2. This material builds up in the brain, and eventually damages nerve cells and causes neurological problems.
Infants usually begin to show signs of the disease between 3 months and 6 months of age. Children with Tay-Sachs disease can become deaf, blind and paralyzed, and usually die by the age of 5.
Tay-Sachs disease is an autosomal recessive inherited disorder, meaning a child inherits one copy of the abnormal gene from each parent. The parents do not actually have the disease, but carry the Tay-Sachs gene and pass it on to the baby. If both parents have the abnormal Tay-Sachs gene, there is a one-in-four chance that their child will inherit the gene from both of them and have Tay-Sachs disease.
Tay-Sachs disease is most common in Ashkenazi Jews. About one in 30 people with this ancestry carry a copy of the gene. Some non-Jewish groups also have a higher chance of carrying the disease. They include people whose ancestors were French-Canadian, from the Louisiana bayou, or from Amish populations in Pennsylvania.
Sinuses are air-filled spaces behind the bones of the upper face: between the eyes and behind the forehead, nose and cheeks. The lining of the sinuses are made up of cells with tiny hairs on their surfaces called cilia. Other cells in the lining produce mucus. The mucus traps germs and pollutants and the cilia push the mucus out through narrow sinus openings into the nose.
A concussion is a short-term disturbance in brain function caused by a head injury. A concussion causes:
Confusion, headache or dizziness
Loss of consciousness lasting less than 30 minutes or no loss of consciousness at all
Loss of memory (amnesia) lasting less than 24 hours
About half of all head injuries happen during motor vehicle accidents. Falls, sports and assaults cause the rest. Alcohol and drug use are major contributing factors.
Most head injuries result from direct trauma (for example, the head hitting the ground or the windshield of a car). In the elderly, serious head injuries can result from even minor falls. Injuries also can occur from rapid acceleration or deceleration, as may happen in a whiplash injury. People who injure their heads often injure their necks, too.
Magnetic resonance imaging or computed tomography (CT) scans of someone with a concussion rarely show obvious signs of brain injury. .
Occasionally, minor head trauma can trigger a more serious problem such as bruising of the brain tissue (brain contusion) or bleeding within the head (subdural hematoma or subarachnoid hemorrhage). Bleeding and other complications of minor head injuries appear to be more common in the elderly and in people taking blood thinners such as warfarin (Coumadin).
Diabetic ketoacidosis is a potentially fatal complication of diabetes that occurs when you have much less insulin than your body needs. This problem causes the blood to become acidic and the body to become dangerously dehydrated. Diabetic ketoacidosis can occur when diabetes is not treated adequately, or it can occur during times of serious sickness.
To understand this illness, you need to understand the way your body powers itself with sugar and other fuels. Foods we eat are broken down by the body, and much of what we eat becomes glucose (a type of sugar), which enters the bloodstream. Insulin helps glucose to pass from the bloodstream into body cells, where it is used for energy. Insulin normally is made by the pancreas, but people with type 1 diabetes (insulin-dependent diabetes) don't produce enough insulin and must inject it daily.
Your body needs a constant source of energy. When you have plenty of insulin, your body cells can get all the energy they need from glucose. If you don't have enough insulin in your blood, your liver is programmed to manufacture emergency fuels. These fuels, made from fat, are called ketones (or ketoacids). In a pinch, ketones can give you energy. However, if your body stays dependent on ketones for energy for too long, you soon will become ill. Ketones are acidic chemicals that are toxic at high concentrations.
In diabetic ketoacidosis, ketones build up in the blood, seriously altering the normal chemistry of the blood and interfering with the function of multiple organs. They make the blood acidic, which causes vomiting and abdominal pain. If the acid level of the blood becomes extreme, ketoacidosis can cause falling blood pressure, coma and death.
Ketoacidosis is always accompanied by dehydration, which is caused by high levels of glucose in the blood. Glucose builds up in the blood if there is not enough insulin to move glucose into your cells. During an episode of ketoacidosis, it is common for blood sugar to rise to a level over 400 milligrams per deciliter. When blood sugar levels are so high, some sugar "overflows" into the urine. As sugar is carried away in the urine, water, salt and potassium are drawn into the urine with each sugar molecule, and your body loses large quantities of your fluid and electrolytes, which are minerals that play a crucial role in cell function. As this happens, you produce much more urine than normal. Eventually it may become impossible for you to drink enough fluids to keep up with amounts that you urinate. Vomiting caused by the blood's acidity also contributes to fluid losses and dehydration.
People with type 1 diabetes are at risk of diabetic ketoacidosis. If you have type 1 diabetes, ketoacidosis can occur because you have stopped taking your insulin injections or because your insulin dose is too low. It can be triggered by an infection or severe physical stress, such as an injury or surgery, because your body can need more insulin than usual during these stresses. Ketoacidosis rarely occurs in people with type 2 diabetes. In most people who have type 2 diabetes, blood insulin levels usually do not get low enough to signal the liver to make ketones.
In about 25% of children with diabetes, symptoms from ketoacidosis are the first sign that they have diabetes.
The human body usually can regulate its temperature. When the body gets too hot, it uses several strategies to cool down, including sweating. But if a person spends too much time in the heat without taking in enough fluids, the body's cooling processes can't work properly. When the body becomes dehydrated, it can no longer cool itself by sweating. When this happens, body temperature can rise high enough to make the person sick.
The first symptoms of heat illness occur as the body temperature climbs above normal, and can include headache, nausea, vomiting, muscle cramps and fatigue. These early symptoms sometimes are called heat exhaustion. If steps are not taken to reduce body temperature, heat exhaustion can worsen and become heat stroke.
Heat stroke is a serious, potentially life-threatening form of heat illness. The body temperature rises to 105 degrees Fahrenheit or higher and you develop neurological changes, such as mental confusion or unconsciousness. At these high temperatures, body proteins and the membranes around the cells in the body, especially in the brain, begin to be destroyed or malfunction. The extreme heat can affect internal organs, causing breakdown of the heart muscle cells and blood vessels, damage to internal organs, and death. There are two main causes of heat stroke:
Exertional heat stroke occurs when someone is vigorously active in a hot environment, such as playing sports on a hot summer day or participating in military training activities. It typically strikes young, otherwise healthy people, those least likely to be concerned about the effects of heat on their health. Because of the lack of concern, early symptoms may be dismissed or ignored.
Nonexertional heat stroke tends to occur in people who have a diminished ability to regulate body temperature, such as older people, very young children or people with chronic illnesses. High heat in the surrounding environment, without vigorous activity, can be enough to cause heat stroke in these people.
Factors that can contribute to heat stroke include:
Dehydration from not drinking enough water
Wearing bulky or heavy clothing, such as firefighting gear, in the heat
Being overweight, which causes the body to generate more heat and reduces the body's ability to cool down
Sleep deprivation, which can decrease the rate of sweating
Being unaccustomed to the heat, such as moving from a cooler climate to a warmer climate
Some medications, most commonly antihistamines (taken for allergies), diuretics (taken for high blood pressure or leg swelling), laxatives (taken to relieve constipation), calcium channel blockers (one type of blood pressure or heart medicine), medicines for Parkinson's disease, some diarrhea treatments and tricyclic antidepressants
Being confined to a poorly ventilated or non-air-conditioned living space
Having had heat stroke in the past
Use of illicit drugs, including cocaine, heroin, amphetamines and ecstasy (MDMA)
Malaria is an infection caused by single-celled parasites that enter the blood through the bite of an Anopheles mosquito. These parasites, called plasmodia, belong to at least five species. Most human infections are caused by either Plasmodium falciparum or Plasmodium vivax.
Plasmodium parasites spend several parts of their life cycle inside humans and another part inside mosquitoes. During the human part of their life cycle, Plasmodium parasites infect and multiply inside liver cells and red blood cells.
Some infected blood cells burst because of the multiplying parasites inside. Many more infected red blood cells are broken down by your spleen or liver, which filter out and remove damaged or aging red blood cells from circulation. Both Plasmodium parasites in the bloodstream and irritants that are released from broken red blood cells cause malaria symptoms.
Most deaths from malaria are caused by P. falciparum, which causes severe disease. Before P. falciparum malaria causes a red blood cell to burst, it can make the surface of the cell stick to other cells like it. This causes the blood to clot within small blood vessels, which can severely damage organs.
People who have lived all their life in a country with a high rate of malaria have typically been exposed to malaria parasites many times. After the first exposure, your immune system begins to protect you, so re-infection may cause few or no symptoms.
Your immune system does not remain active against malaria for more than a few years if you are not exposed again. This explains why people can live for years in the tropics without being bothered by malaria. However, people from the tropics who spend several years in another country may lose their immune protection.
Pertussis, also known as whooping cough, is a highly contagious bacterial infection that causes violent coughing. The coughing makes it hard to breathe and produces a deep "whooping" sound.
Pertussis is caused by the Bordetella pertussis or Bordetella parapertussis bacteria. Droplets of the bacteria move through the air when an infected person sneezes, coughs or talks. This is how pertussis spreads from person to person.
Pertussis can occur at any age. Serious illness is most common in infants and young children. Older children, adolescents and adults usually have milder symptoms.
The number of pertussis cases in the United States has increased in recent years. There were more than 17,000 reported cases of pertussis in 2009.
A pneumothorax is commonly known as a collapsed lung. Normally, the outer surface of the lung sits next to the inner surface of the chest wall. The lung and the chest wall are covered by thin membranes called pleura.
A collapsed lung occurs when air escapes from the lungs or leaks through the chest wall and enters the space between the two membranes (pleural cavity). As air builds up, it causes the nearby lung to collapse.
A collapsed lung is most often caused by an injury to the lungs or chest wall, such as:
A penetrating injury, such as a knife or gunshot wound
Blunt trauma from a fall or car accident
Medical procedures, such as removal of fluid from the pleural cavity with a needle (thoracentesis) or a lung biopsy
Occasionally, a lung will collapse without any direct injury to the lung or chest. This is called a spontaneous pneumothorax. This is more likely to happen in people with lung disease.
It is particularly common in emphysema, which causes air-filled sacs, called blebs, to form. When one of these sacs bursts, air is released into the pleural cavity, causing the lung to collapse. It also occurs in people with asthma, cystic fibrosis and pneumonia.