IgG Deficiency
Immunoglobulin G Class (IgG)

Author: Gianpiero Pescarmona
Date: 22/04/2014


Disease caused by a deficiency of IgG

The greatest part of patients that suffer of immune deficiency by IgG levels, has total IgG and other antibodies normal or nearly normal levels, but with a decreased responsiveness to specifical antigens. Most frequent symptoms are associated with respiratory infections, chronic or recurrent otitis of the middle ear, pneumopathy and chronic meningitis.

Since the IgG1 constitute 70% of total IgG, an isolated deficiency of IgG1 is not regarded as a deficiency of a subclass. The combined deficiency of IgG2 or IgG3, with or without IgG4 deficiency is the most common deficit borne by subclasses. Patients with IgG2 deficiency often have weak antibody responses against polysaccharide antigens and / or an associated deficiency of IgA (<5mg/dl).

The isolated IgG4 deficiency (asymptomatic) is present in a large number of individuals.

In young children, the deficits of the subclasses may be transient and disappear with the growth. The disorder is called transient hypogammaglobulinemia of childhood. There were described some patients with impaired ability to respond to polysaccharide antigens but with normal levels of IgG subclasses.

Some patients have a deficit of Immunoglobulins G correlated with a defective gene, this disease is caldded Bruton's Agammaglobulinemia , also, Agammaglobulinemia Chromosome X – Linked.

This disease affects infants during the first months of life to the point that the first infections are contracted for a few months after birth. Most recurrent infections are: lungs, paranasal sinuses and bone chronical piogenic infections, supported by micro-organisms such as pneumococcus, the streptococcus and haemophilus. Patients are also predisposed to infections by poliovirus and vaccine-induced chronic encephalitis by echovirus.

Some infants develop arthritis that disappears with the treatment with IG.

The inheritance linked to chromosome X is shown in 20% of cases.

Flaw borne gene for BTK (Bruton tyrosine kinase of) located in the region Xq22 prevents differentiation of pre-B cells in cell B.

In each of the family members are seen several variations of the defective gene

Figure 4: Location of the BTK gene on Xq22

Therapy: Adnminisistration for the entire life of Immunoglobulins for intravenous or intramuscular injection at lower doses to prevent recurrent infections. During each episode of infection is mandatory recuring to a massive antibiotic therapy. The most severe forms requiring continues antibiotic administration, even in the absence of suspected infections. Despite these measures, many patients develop persistent sinusitis, bronchitis and bronchiettasis. These patients have an increased susceptibility to the development of malignancies.

Some patients may, however, develop immunodeficiency in the course of their life, in particular between 20 and 30. The distinctiveness between the common variable immunodeficiency (CVI) and the linked agammaglobulinemia the X chromosome is the presence of normal B cells. The cellular immunity is usually efficient, but in some patients may be endangered, in other one are described immunoregolatory dependent alterations of T-cell. In these patients and their families are common autoimmune disorders, including Addison’s disease and autoimmune thyroiditis. Sometimes there could be diarrhea, malabsorption and lymphoid nodular hyperplasia of the gastrointestinal tract, and an increased propensity towards the development of carcinomas and lymphomas (approximately 10% more than the normal population).

The immunological mechanisms that lead to CVI is different, for example there can be an excessive T-suppressing activity, low T-helper activity, intrinsic defects of B cell function and the presence of autoantibodies directed against the B cells or T.

As in in the agammaglobulinemia chromosome X-linked, is essential recur to an immunoglobulin therapy forthe entire life and using antibiotics in the treatment of any infectious episode.

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