Type 1 diabetes is an autoimmune disease, which means the body's immune system attacks the body instead of outside invaders. In this case, the immune system destroys insulin-producing cells (beta cells) in the pancreas. Over time, the amount of insulin made by the beta cells decreases to the point where blood sugar becomes dangerously high.

What causes the immune system to attack the beta cells remains a mystery. Current thought is that a genetic (inherited) factor makes a person predisposed to the disease, and an environmental factor triggers the start of the disease. Viral infections and diet are two possible triggers. The Coxsackie, rubella and mumps viruses are all possible triggers because the disease sometimes starts after one of these infections. Cow's milk is one dietary factor that may be related to the development of type 1 diabetes. Babies who are breastfed have a lower risk of type 1 diabetes than babies who are not breastfed. Type 1 diabetes is not caused by the amount of sugar in a person's diet before the disease develops.

Type 1 diabetes is a chronic (long-lasting) disease that typically begins before age 35. It is not unusual for children ages 1 to 4 years to develop the disease, but it is diagnosed most commonly between ages 10 and 16. Type 1 diabetes affects males and females in equal numbers.

Symptoms

Symptoms usually come on suddenly and strongly, and include extreme thirst, frequent urination and vomiting. Children may start to wet the bed, after having been dry at night for some time. Weight loss, with no loss of appetite, can be one of the first signs of type 1 diabetes in children. If the disease is left untreated, sugar and acid (ketone) buildup in the blood can cause weakness, confusion, coma and even death.

Type 1 diabetes affects all body systems and can cause serious, potentially life-threatening complications, including:

• Eye damage (retinopathy) - In this disorder, tiny blood vessels at the back of the eye are damaged by high blood sugar. Caught early, retinopathy can be stopped by tightly controlling blood sugar and by using laser therapy. If blood sugar remains too high, retinopathy eventually causes blindness.

• Nerve damage (neuropathy) - High blood sugar can damage nerves, leading to pain or numbness of the affected body part. Damage to nerves in the feet, legs and hands (peripheral neuropathy) is most common. Nerves that control body functions, such as digestion and urination, also can be damaged (autonomic neuropathy).

• Foot problems - Sores and blisters commonly occur on the feet of people with diabetes. If peripheral neuropathy causes numbness, a sore may not be noticed and it can become infected. Blood circulation can be poor, leading to slow healing. Left untreated, a simple sore can lead to gangrene (the death of soft tissue due to lack of blood flow), and sometimes the leg or a portion of it may need to be removed surgically (amputated).

• Kidney disease (nephropathy) - High blood sugar can damage the kidneys. If blood sugar remains high, it can lead to kidney failure.

• Heart and artery disease (atherosclerosis) - Heart and blood vessel problems can result from high blood sugar. People with type 1 diabetes are more likely to have heart disease, strokes and problems related to poor circulation.

• Diabetic ketoacidosis - This occurs when acidic substances called ketones are made by the body as a substitute energy fuel instead of glucose. Symptoms include nausea and vomiting, abdominal pain, fatigue, lethargy and, eventually, coma and death.

• Hypoglycemia - Low blood sugar, called hypoglycemia, can result if too much insulin is taken or not enough carbohydrates are taken in to balance the insulin. Symptoms include weakness, dizziness, trembling, sudden sweating, headache, confusion, irritability, and blurry or double vision. Hypoglycemia can lead to coma if it is not corrected by eating or drinking carbohydrates, or by an injection of glucagon (a substance that makes the liver release glucose into the bloodstream).