14th February 2024

Examples

Common variable immunodeficiency (CVID)

Consists of a group of diseases characterised by a deficiency in immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM). The clinical presentation can vary depending on which immunoglobulins are affected, but some patients have a deficiency of all three. Patients with CVID are more susceptible to sinuses and respiratory tract bacterial and viral infections. There is also an increased susceptibility to GI infections such as Campylobacter and Giardia. Patients often respond poorly to vaccines as they cannot produce adequate antibodies. Diagnosis is made by measuring immunoglobulin levels, and the primary treatment is with intravenous or subcutaneous immunoglobulin infusions.

X-linked agammaglobulinaemia

An X-linked disorder caused by failure of B cell maturation resulting in a complete absence of B cells and, therefore, no antibodies. Patients suffer recurrent pyogenic sinus, lung and skin infections, particularly from encapsulated bacteria and viral central nervous system infections. The diagnosis is made by confirming low immunoglobulin levels and the absence of B cells on flow cytometry. Treatment is with immunoglobulin replacement and prompt initiation of antibiotics in infection. Live virus vaccines are contraindicated.

Selective IgA deficiency

It is the most common primary antibody deficiency defined by undetectable IgA levels with normal levels of other immunoglobulins. 85 – 90% of patients with Selective IgA deficiency are asymptomatic, whereas the remainder have an increased propensity to recurrent sinusitis, respiratory infections, allergies and autoimmune disorders. Recurrent infections tended to be bacterial, and there was an association between IgA deficiency and autoimmunity with idiopathic thrombocytopenic purpura, haemolytic anaemia and systemic lupus erythematosus (SLE) as well as Coeliac disease and thyroid disease. Diagnosis is made by confirming undetectable IgA compared with normal other subclasses of immunoglobulins. Treatment is not indicated for asymptomatic patients, and those with recurrent infections should be treated promptly or considered for prophylactic antibiotics.