Multiple Sclerosis (MS)

Multiple Sclerosis (MS), chronic, unpredictable, and often progressive disease of the central nervous system that attacks and destroys tissues in the brain and spinal cord. There are several forms of MS, but all forms affect nerve function, resulting in problems ranging from mild numbness and difficulty walking to paralysis and blindness. Although MS can occur at almost any age, the disease usually strikes people who are between the ages of 20 and 40. For unknown reasons, MS is more common in Caucasians, women, and people living in temperate, rather than tropical, climates.

The cause of MS is unknown, but genetics, an infectious agent, a faulty immune system, or a combination of these factors appears to play a role in why a person contracts the disease. MS is thought to occur in people who have a genetic susceptibility for the disease, demonstrated by cases of MS occurring within the same family too frequently to be accounted for simply by chance. However, studies of identical twins imply that a genetic predisposition is not the sole cause. A genetically susceptible person must encounter a second factor that will later trigger the development of MS.

Symptoms include weakness, tingling, numbness, fatigue, incoordination, balance and vision problems, tremors, muscle stiffness known as spasticity, slurred speech, depression, bowel or bladder problems, sexual dysfunction, problems with memory or reasoning, and partial or complete paralysis. Although MS can cause severe discomfort and disability, it does not usually shorten life span.

MS can be difficult to diagnose, as no single laboratory test clearly identifies the disease. It is primarily diagnosed by reviewing a person’s medical history and giving a neurological exam that tests for abnormal reflexes, muscle weakness or incoordination, alterations of sensation, damage to the optic nerve, and other signs of brain or spinal cord damage.

Autoimmune Diseases

Autoimmune Diseases, illnesses in which the immune system reacts to normal components of the body as if they were foreign substances and produces antibodies against them.

Antibodies are manufactured by cells called lymphocytes. It is thought that, during development of the embryo, lymphocytes capable of reacting with the body's own tissues are somehow inactivated so that the self is distinguished from the nonself and is not destroyed by antibodies. Self-reactive lymphocytes can still be found in some adults, however, which suggests that they are actively suppressed in some way rather than eliminated. Another mechanism for protecting components of the self from destruction is sequestration during early development. Mature sperm cells, for example, do not appear until after the immune system has matured and are then automatically separated from the bloodstream. After vasectomy, these cells enter the bloodstream, where they can provoke formation of antibodies against themselves (autoantibodies).

One theory to explain autoimmune disease proposes that suppression of reaction against the self is disrupted when viruses infect the antibody-forming cells. In the infectious form of mononucleosis (see Infectious Mononucleosis), in which lymphocytes are invaded by a virus, antibodies against a variety of body tissues are found in the bloodstream. Rheumatic heart disease is believed to be a result of childhood infection (see Rheumatic Fever) by streptococcal bacteria, which have a surface molecular arrangement identical to one found in heart muscle; antibody formed against the bacteria can also damage the heart.

In most other autoimmune diseases the cause of antibody formation is unknown. Persons with myasthenia gravis make an antibody that blocks the transmission of nerve impulses to muscle; this causes the muscle weakness and breathing difficulty associated with the disease. In autoimmune hemolytic anemia, the red blood cells are destroyed by autoantibodies. Persons with lupus erythematosus make antibodies that attack cell components, including genetic material. Clumps of matter formed by antibodies bound to the cell components can damage the kidneys. The blood of some persons with arthritis contains rheumatoid factor, an antibody that binds to other antibodies in the blood; whether this factor also causes the joint injury of arthritis is not known.

Lupus, arthritis, and the skin diseases scleroderma and dermatomyositis are called collagen diseases because of the damage the associated antibodies cause to connective tissue, which is made up of collagen.

A few severe cases of diabetes are caused by an antibody that destroys insulin-forming cells in the pancreas. Another antibody attacks the thyroid gland, producing chronic thyroiditis. Addison's disease in some cases may result from autoimmune destruction of the adrenal gland.

One of the most intensively studied autoimmune diseases is multiple sclerosis. In this illness the myelin sheath covering the spinal cord is destroyed, leading to difficulty in walking and other movements. The damage in multiple sclerosis is not produced by an autoantibody but by a lymphocyte that reacts directly with the protective sheath.

Autoantibodies are often found in the blood of older persons who have no disease, a phenomenon that is not understood.

Treatment of autoimmune diseases usually entails therapy with steroids , which suppress the immune system. Currently under investigation is a procedure called plasmapheresis, in which the patient's blood is passed through a machine that removes gamma globulin, the blood fraction that contains antibodies.

Jaundice

Jaundice or Icterus, yellowing of the skin, conjunctivae, and mucous membranes caused by excessive amounts of bile pigments in blood tissues. These pigments, normally present in blood as a result of the breakdown of hemoglobin in red blood cells, are filtered through the liver and excreted in feces (see Gallbladder). Excessive amounts of these pigments produce four types of jaundice.

In hemolytic jaundice there is increased production of bile pigment because of red blood-cell damage. This damage can be caused by antibodies created by a mismatched blood transfusion. In infants the antibodies can be caused by prenatal mismatch between the Rh factor in the infant's blood and that of the mother.

Newborns can also be jaundiced as a consequence of the condition known as hyperbilirubinemia. In these cases, there is a temporary defect in synthesis of the enzyme that breaks down bile to an excretable form.

Hepatocellular jaundice occurs when liver cells are damaged either by viruses (see Hepatitis), or by excessive intake of alcohol, and lose the ability to process pigment.

Obstructive jaundice follows physical obstruction of the ducts that transport pigment from the liver to the intestine. Blockage can be due to gallstones, tumor, or inflammation.

Hepatitis

Hepatitis, inflammation of the liver caused by viruses, bacterial infections, or continuous exposure to alcohol, drugs, or toxic chemicals, such as those found in aerosol sprays and paint thinners. Hepatitis can also result from an autoimmune disorder, in which the body mistakenly sends disease-fighting cells to attack its own healthy tissue, in this case the liver. No matter what its cause, hepatitis reduces the liver’s ability to perform life-preserving functions, including filtering harmful infectious agents from the blood, storing blood sugar and converting it to usable energy forms, and producing many proteins necessary for life.

Symptoms of hepatitis vary significantly depending on the cause and the overall health of the infected individual. Some cases of hepatitis have few, if any, noticeable symptoms. When symptoms are present, they may include general weakness and fatigue, loss of appetite, nausea, fever, and abdominal pain and tenderness. Another symptom is jaundice, a yellowing of the skin and eyes that occurs when the liver fails to break down excess yellow-colored bile pigments in the blood.

In acute hepatitis, symptoms often subside without treatment within a few weeks or months. About 5 percent of cases develop into an incurable form of the disease called chronic hepatitis, which may last for years. Chronic hepatitis causes slowly progressive liver damage that may lead to cirrhosis, a condition in which healthy liver tissue is replaced with dead, nonfunctional scar tissue. In some cases, cancer of the liver develops.

How STIs are Transmitted

STIs are transmitted by infectious agents—microscopic bacteria, viruses, parasites, fungi, and single-celled organisms called protozoa—that thrive in warm, moist environments in the body, such as the genital area, mouth, and throat. Most STIs spread during sexual intercourse (vaginal or anal), but other forms of sexual contact, such as oral sex, can also spread disease.

Some STIs are transmitted in ways other than by sexual contact. Certain viral STIs, such as AIDS and some types of hepatitis, may be transmitted by contact with infected blood. For instance, viral STIs may pass between people who share infected needles, and a person can become infected from a transfusion of infected blood. Some STIs may pass from an infected mother to her child. Infection may occur before birth, when the infectious agent crosses the placenta (organ in a pregnant woman’s uterus that links the blood supplies of mother and baby) and enters the baby’s bloodstream. Infection also may occur during childbirth, as the baby passes through the birth canal, or after birth, when the baby consumes infected breast milk. STIs cannot be transmitted through shaking hands or other casual contact, or through contact with inanimate objects such as clothing or toilet seats.