Human normal immunoglobulin preparations administered intravenously (IVIg) or subcutaneously (SCIg) are used in the treatment of patients who have no, or very low levels of, antibody production. This may be due to a genetic disorder, to disease, or to treatment such as chemotherapy.
PID results from the failure of the immune system to produce sufficient antibodies to fight infection. The most common types of PID are:
SID is a shortage or complete lack of antibodies which results from the effects of another illness. An example of an SID is Chronic Lymphocytic Leukaemia (CLL). It is a disease that prevents B-cells from working properly. B-cells are the cells which produce antibodies. Although patients with CLL usually have more B-cells than normal, these are not working properly so the patients often lack sufficient antibodies to fight infection. For patients with low levels of antibodies and recurrent infections, regular doses of IVIg or SCIg are needed to maintain antibody levels high enough to protect against infection.
As with PID, treatment with IVIg or SCIg replenishes antibody levels, allowing patients to fight infection efficiently. Regular doses of IVIg or SCIg are needed as long as the condition persists.
ITP is a disease which results in a shortage of platelets. It is caused by the patient's own antibodies attacking his or her platelets. Low levels of platelets can result in bleeding problems. In children, ITP often appears after an infection and usually goes away within a few weeks without treatment. In adults, ITP is less likely to go away spontaneously and becomes chronic. Spontaneous remission is less likely with adults and, if platelet counts fall very low or there are bleeding tendencies, treatment may be needed. There are many possible treatments but IVIg may be used because it blocks the normal breakdown of platelets by the spleen.
Kawasaki Disease is thought to follow an infectious disease and mainly appears in children, resulting in inflammation of the blood vessels and other tissues, such as heart muscle. About 25% of affected children develop heart problems during the later stages of the illness. A high dose of IVIg given early in the course of the disease in conjunction with aspirin can prevent coronary artery damage. The mode of action of IVIg in this condition is not understood, but it is extremely effective.
GBS is a short-term (acute) inflammation of the nerves that control the arms and legs. Although the exact cause of GBS is not fully understood, it often follows an infectious disease, e.g. of the gastro-intestinal tract. It is known that the symptoms are caused by the patient's own antibodies attacking the nerves to the limbs. The damage caused by the antibodies accounts for the tingling and short term paralysis symptomatic of GBS. IVIg can be used in the treatment of this condition, the wide variety of antibodies infused helping to cancel the effect of the nerve-damaging antibodies.
CIDP is an inflammatory neuropathy and autoimmune disease. An aberrant immune response causes damage to the myelin sheath of the peripheral nerves. The exact mechanisms by which this happens are still not clearly defined. CIPD is characterised by progressive symmetric weakness and impaired sensory function in the legs and arms. CIDP is closely related to Guillain-Barré syndrome (GBS) and it may be considered the chronic counterpart of that acute disease. Not all patients respond to treatment with current therapies aimed at arresting immunopathogenic mechanisms.
MMN is a rare, chronic, immune-mediated neuropathy. MMN is characterised by progressive, asymmetric muscle weakness and atrophy. Signs and symptoms include weakness in the hands and lower arms, cramping, involuntary contractions or twitching and atrophy of affected muscles. MMN is thought to be due to an abnormal immune response, but the underlying cause is not clear. MMN usually responds to IVIg treatment.