Immune Diseases CIDPUSA.ORG

IMMUNE -DEFENSES

Return to previous page

G E R MS

• Bacteria are tiny living organisms. Each bacterium consists of a single cell, but bacteria often live in colonies. Most are harmless or even beneficial, but some can cause illness and death
• Bacteria are responsible for many respiratory, skin,and bone infections. Examples of infection-causing bacteria include "strep"(Streptococcus)and" staph"(Staphylococcus)
• Viruses consist of the barest essentials: a strand of genetic material, either DNA or RNA, surrounded by a protein coat. Some viruses also have an outer envelope. Viruses are so simple that, in order to reproduce, they need to invade a living cell and use the cell's machinery

Different types of viruses target different types of cells. Some viruses kill thecell they invade.Others permanently change the way the cell behaves Viruses cause the flu (ori nfluenza, a highly contagious respiratory infection), colds, polio, hepatitis (liver inflammation),and measles. A single virus family, Herpes viruses, causes everything from cold sores to chickenpox

• Parasites live, grow, and feed on other organisms, which serve as their "hosts."Parasite scome in many shapes and sizes, and they cause a wide range of diseases

  Microscopic one-cell parasites known as Cryptosporidium and Giardialamblia cause diarrhea and inflammation of the digestive system. Pneumocystiscarinii can cause pneumonia,and Toxoplasmagondii can produce brain inflammation

• Mycoplasma are simpler than bacteria but more complex than viruses.They are the smallest known organisms that can live without a host. Mycoplasma can cause pneumonia and a type of arthritis
• Fungi, which are primitive plant forms,include yeasts and molds. As a cause of disease, they are especially dangerous for persons with impaired immunity

A fungus called Candida albicans causes thrush,which commonly forms a white mat coating on the insideof the mouth in severely immunodeficient people.This fungus may also cause esophagitis,diaper rash,  blood infection.

Cryptococcus can cause meningitis,an inflammation of the membranes surrounding the brain and spinalcord. Aspergillus, an ordinarily harmless mold, can cause severe infections in those with PI, especially infections of the lung.

One possibility might be to replacea mutated gene through gene therapy. Another way might be to supply the missing protein as a medicineS I G N S  A N D   SY M P T O M S

The most common problem in PI disease is an increased susceptibility toi nfection. For people with PI,infections may becommon, severe, lasting, or hard to cure.

EvEven healthy youngsters may get frequent colds, coughs, and earaches. For example, many infants and young children with normal immunity have one to three ear infections per year. Children with PI, however,can get one infection after another. Or they get two or three infections at a time. Weakened by infection, the child may fail to gain weight or fall behind in growth and development

Despite the usual antibiotics, the infections of PI often drag on and on, or they keep coming back-that is, they become chronic. One common problem is chronic sinusitis (infection and inflammation of the sinuses, air passages in bones of the cheeks, forehead, and jaw). Another common problem is chronic bronchitis (infection and inflammation of the airways leading to the lungs)

D N A ,  G E N E S ,A N D  C H R O M O S O M E S

All our traits-height, eye color, foot size-are determined by the genes that we inherit from our parents. A geneis a working subunit of DNA.DNA is like a huge database, made up of millions of chemical building blocks. DNA resides in the core of every cell, and it carries a complete set of instructions, or blueprint, for making everything the cell will ever need.
The DNA in each human cell contains about 100,000 genes. Each gene encodes the instructions that allow the cell to make one specific product-for example, a protein such as anenzyme. (Proteins are major components of all cells. Enzymes are proteins which help carryout chemical reactions.)When genes are working properly, our bodies develop correctly and work well.But small changes, or mutations, in just one gene sometimes can have huge effects, leading to birth defects and other diseases.
DNA is packaged in structures known as chromosomes.Chromosomes come in pairs, and a normal human cell contains 46 chromosomes. These consist of 22 pairs of "autosomes" and two "sex chromosomes," X and Y. A female has twoX chromosomes while a male has one X and one YWe inherit one chromosome of each pair from our mother and the other from our father. Since genes are lined up on the chromosomes, we thus inherit two copies of most genes, one from each of our parents. If one copy of a gene is not working properly, its partner from the other parent can often compensate. However, this is not possible if both copies of the gene are defective or, inthe case of an X chromosome gene defect in a boy, where there is only one X chromosome

Serious infections, especially bacterial infections, may cause a youngster to be hospitalized repeatedly. Pneumonia is an infection of the smallest airways and airsacs in the lungs, whichprevents oxygen from reaching the blood and makes breathing hard. Meningitis, an infection of the membranes that surround the brain and spinal cord, causes fever and severe headache, and can lead toseizures, coma, and even death. Osteomyelitis is an infection that invades and destroys bones. Cellulitis is a serious infection of connective tissues just beneath the skin

Some people with PI develop blood poisoning, an infection that flourishes in the bloodstream and spreads rapidly through the body. Some people may develop deep abscesses, pocketsof pus that form around infections in the skin or in body organs

Some children with PI are infected with germs that a healthy immune system would hold in check. These are known as "opportunistic" infections because the germs take advantage of the opportunity affordedby a weakened immune system. Such an unusual infection may be the tip-off to an immunodeficiency

For example, Pneumocystis carinii is a microscopic parasite that infects many healthy people without making them sick. But when the immune system is compromised, Pneumocystis can produce a severe form of pneumonia

Toxoplasma is another widespread parasite that usually produces no disease. In persons with a weakened immune system, it causes toxoplasmosis, which can be a life-threatening infection of the brain that can causeconfusion, headaches, fever, paralysis, seizures, and coma.

 Please continue to next page S I G N S   A N D   S Y M P T O M S OF IMMUNE DEFICIENCY chronic sinusitis