Dr Ira Shah
Consultant Pediatrician, Nanavati Hospital and B.J.Wadia Hospital for Children, Mumbai
Editor - Pediatric Oncall

What is IgG subclass deficiency?
IgG subclass deficiency is a type of primary immunodeficiency where subclasses of IgG are deficient leading to recurrent infections. The body produces 5 types of immunoglobulins - IgA, IgM, IgD, IgE & IgG which help to fight infection. IgG further is divided into 4 subtypes called IgG subclasses IgG1, IgG2, IgG3, IgG4 based on their molecules. IgG1 & IgG3 subclass antibodies help to protect against diphtheria, tetanus and viruses whereas IgG2 helps to protect against pneumococcus & hemophilus influenza. Thus deficiency of certain IgG subclass renders the individual susceptible to certain kind of infections.

What are the normal levels of various IgG subclasses?
IgG1 is the predominant IgG subclass and forms 60-70% of IgG is blood followed by IgG2 (20-30%) and then IgG3 & IgG4 (1-3%). Children tend to have lower levels of IgG as compared to adults and reach adult levels by 10 years of age. (Adult levels of IgG1 & IgG3 are reached by 5-7 years of age. Some children may have low levels of IgG subclass which may normalize as they grow leading to transient subclass deficiency.

What are the symptoms of IgG subclass deficiency?
Children with IgG subclass deficiency tend to have recurrent ear infections, sinusitis, bronchitis and pneumonia.

Which is the commonest IgG subclass deficiency?
IgG2 subclass deficiency is commonly seen in children whereas IgG3 subclass deficiency is seen in adults. IgG4 deficiency usually is seen along with IgG2 deficiency and isolated IgG4 deficiency rarely occurs.

How is the diagnosis of IgG subclass deficiency made?
Diagnosis of IgG subclass deficiency is established by detecting low levels of one or more IgG subclass in the blood with normal levels of IgG, IgA & IgM. Sometimes IgG2 & IgG4 deficiency can occur with IgA deficiency or IgE deficiency. Since many children outgrow their IgG subclass deficiency as they grow older, retesting may be required every 4-6 months.

What is the inheritance of IgG subclass deficiency?
No clear cut genetic defect has been observed in IgG subclass deficiency.

What is the treatment of IgG subclass deficiency?
Treatment of infections with antibiotics should be promptly instituted. Immunoglobulin replacement therapy may be considered in whom infections cannot be controlled by antibiotics.

Last Updated: 1^st September 2011