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More Diseases & Conditions
More Diseases & Conditions Articles
Hemophilia is an inherited disorder. It prevents blood from clotting properly. People with hemophilia bleed longer than usual. This bleeding can range from mild to severe. In severe cases, people with hemophilia can bleed to death.
Because of the way in which hemophilia is inherited, it almost exclusively affects men. Women can get it, but it is very rare.
Clotting is the process in which the blood thickens or congeals. This prevents a cut or other injury from bleeding endlessly.
Clotting factors are substances in the blood that help the blood to clot. People with hemophilia do not have enough clotting factors.
Blood clotting involves two sets of factors. One set works with specialized blood cells called platelets. Platelets play a central role in blood clotting. The other set of factors involves the coagulation system. Coagulation is a coordinated series of chemical reactions that clots and stops the bleeding.
Myelodysplastic syndromes (MDS) are diseases in which the bone marrow does not make enough healthy blood cells. Bone marrow is the soft, inner part of bones. Normally, it produces three kinds of blood cells:
red blood cells, which carry oxygen
white blood cells, which fight infection and disease
platelets, which help prevent bleeding by causing blood to clot.
Healthy bone marrow makes immature cells called stem cells that develop into red and white blood cells and platelets.
In MDS, the bone marrow cannot produce the right kind of blood cells. These abnormal cells either die in the bone marrow or soon after they enter the bloodstream. As a result, people with MDS don't have enough healthy blood cells and are said to have low blood cell counts. This can lead to:
anemia, caused by not enough red blood cells
infections, caused by not enough white blood cells
bleeding and bruising, caused by not enough platelets.
Many experts consider MDS an early stage of cancer. In about 30% of patients, the disease will develop into acute myeloid leukemia (AML), a cancer of bone marrow cells.
In most cases, the cause of MDS is not known. The biggest risk factor for MDS is having had treatment for cancer with chemotherapy and radiation therapy. Exposure to certain chemicals has also been linked to MDS. Some people may be born with a tendency to develop MDS.
Most patients with MDS are over age 60. The disorder is slightly more common in men than women. It is also slightly more common in whites than in other racial groups.
Parkinson's disease (PD) is a disease of the central nervous system. It causes problems with body motions, including:
Rigidity (muscle stiffness)
Slowed body movements
PD develops when certain nerve cells (neurons) in the brain die. These are neurons that produce a chemical called dopamine. Dopamine helps relay messages between areas of the brain that control body movement.
When these neurons die, abnormally low levels of dopamine are produced. This makes it difficult to control muscle tension and muscle movement.
The human immunodeficiency virus (HIV) weakens the body's immune defenses by destroying CD4 (T-cell) lymphocytes, a type of white blood cell. T-cells normally help guard the body against attacks by bacteria, viruses and other germs.
When HIV destroys CD4 cells, the body becomes vulnerable to many different types of infections. These infections are called "opportunistic" because usually they only have the opportunity to invade the body when the immune defenses are weak. HIV infection also increases the risk of certain cancers, illnesses of the brain and nerves, body wasting, and death.
The range of symptoms and illnesses that can happen when HIV infection severely weakens the body's immune defenses is called acquired immunodeficiency syndrome or AIDS.
Normally, the brain's nerve cells (neurons) communicate with one another by firing tiny electric signals that pass from cell to cell. The firing pattern of these electric signals reflects how busy the brain is. The location of these signals indicates what the brain is doing, such as thinking, seeing, feeling, hearing, controlling the movement of muscles, etc. A seizure occurs when the firing pattern of the brain's electric signals suddenly becomes very abnormal and unusually intense, either in an isolated area of the brain or throughout the brain.
If the whole brain is involved, the electrical disturbance is called a generalized seizure. This type of seizure used to be called a grand mal seizure. The most easily recognizable symptom of a generalized seizure is the body stiffness and jerking limbs known as tonic-clonic motor activity.
Body lice are small, parasitic insects found mainly on the clothing of infested people, and occasionally on their bodies or bedding. Although they are related to head lice, and look almost exactly the same, body lice rarely infest the head hair. Instead, they spend most of their life on an infested person's clothing, crawling onto the skin to feed on the host's blood one or more times a day.
Female lice glue their eggs on the seams of clothing worn near the skin, where body heat allows them to hatch in about a week. A female louse can produce 300 or more eggs in her adult life, at a rate of about 10 per day. Eggs require temperatures between 75° and 100° Fahrenheit to hatch. Hatchlings develop to the adult stage in about nine days if they remain close to the host, but this can take as long as four weeks if the person takes the clothing off.
Most body lice are on homeless or destitute adults who rarely change their clothes. Children rarely have body lice.
Meningitis is an inflammation of coverings (meninges) of the brain and spinal cord. Most often it is caused by a viral or bacterial infection. Other infectious agents such as fungi can also cause meningitis. Rarer causes of meningitis include atypical drug reactions and systemic lupus erythematosus. Viral, or aseptic, meningitis is the most common type. In general, viral meningitis is not directly contagious. Anyone can get viral meningitis, but it occurs most often in children. Many different viruses can cause meningitis; an enterovirus tends to be the usual culprit.
Viral meningitis due to enterovirus peaks in mid-summer through early autumn. But it can occur any time of the year. Except for the rare case of herpes meningitis, viral meningitis will resolve on its own after 7 to 10 days.
Bacterial meningitis, formerly called spinal meningitis, is a very serious and potentially fatal infection. It can strike very healthy people, but infants and older people are more susceptible. In the past, the three most common types of bacterial meningitis were caused by Neisseria meningitidis, Haemophilus influenza and Streptococcus pneumoniae. Now that we have very effective vaccines to help prevent all three types, bacterial meningitis in otherwise healthy children and adults occurs less often.
Polio is a highly contagious infection caused by the poliovirus. Most people infected with the virus develop no symptoms from it. However, in a small percentage of infected people, the virus attacks nerve cells in the brain and spinal cord, particularly the nerve cells in the spinal cord that control muscles involved in voluntary movement such as walking. Permanent paralysis occurs in one out of every 200 cases of polio. Polio is also called poliomyelitis.
The infection spreads through direct contact with virus particles that are shed from the throat or in feces. The disease has been virtually wiped out in the Western hemisphere since the introduction of the inactivated polio vaccine (the "Salk vaccine") in 1955 and the oral, live vaccine (the "Sabin vaccine") in 1961.
There are two forms of polio:
Minor poliomyelitis (also called abortive poliomyelitis) occurs primarily in young children, and is the more common of the two forms. The illness is mild, and the brain and spinal cord are not affected. Symptoms appear three to five days after exposure to the virus and include slight fever, headache, sore throat, vomiting, lack of appetite, and a general feeling of illness and discomfort.
Major poliomyelitis is a more severe illness that develops approximately 7 to 14 days after exposure to the virus. Symptoms include fever, severe headache, stiff neck and back, and deep muscle pain. Some people experience temporary abnormalities of skin sensation. Muscle spasms and a tendency to retain urine are common.
Muscle weakness and paralysis may develop rapidly or gradually during the time fevers occur, but paralysis does not continue to get worse afterwards. The disease most commonly affects the strength of muscles of the legs. It can also affect strength in the muscles of the arms and abdomen. When polio affects strength in the muscles of the neck and throat, it causes difficulty speaking and swallowing. The most life-threatening form of polio causes weakness of the muscles in the chest that are needed for breathing. The virus also can sometimes affect the parts of the brain that control breathing. When a polio victim develops breathing trouble, they need machines to help breathe for them.
Normally, vaginal discharge is clear or white. It may become stretchy and slippery during ovulation, about two weeks after your menstrual period. A change in the color or amount of discharge, accompanied by other symptoms, may indicate that you have an infection.
The vagina normally contains bacteria. Bacterial growth is controlled and affected by many different factors, such as acid level (pH) and hormones. Anything that upsets this balance may increase your risk of infection or overgrowth of any of the normal bacteria or by yeast.
Influenza (the flu) is a respiratory infection. It is caused by the influenza virus. Influenza typically is spread by air or by direct contact from one person to another. Influenza virus is very contagious.
Most influenza cases occur during epidemics. Epidemics peak during the winter months. A particularly widespread and severe epidemic is called a pandemic.
Compared with other viruses, influenza can strike remarkably large numbers of people in a relatively short time. In the developed nations, about 10-15% of the people get the flu each year. During severe epidemics, a greater fraction of the population gets sick.
The most common types of influenza virus are A and B. Influenza A is the one usually responsible for the annual epidemics. Most people get multiple flu infections during their lives. With many other types of infections, having the disease once protects against a second infection. That is because the body's immune system remembers the returning virus. It attacks it immediately, and rapidly eliminates it.
With influenza, the virus usually has mutated (changed) somewhat since the first infection. The change is enough to fool your immune system. As a result, the immune system responds slowly. By the time the immune response is in full gear, millions of the body's cells are already infected.