A 13-month-old boy is hospitalized with high fever, cough, and decreased oral intake. Diagnostic work up reveals pneumococcal pneumonia (Figure 218-1). He responds well to intravenous and oral antibiotic treatment with complete resolution of symptoms. His birth history is unremarkable with a normal full-term delivery and birth weight (3.3kg). At 4 months of age, he developed otitis media successfully treated with oral antibiotics. Since then he has had numerous upper respiratory and ear infections. At 8 months of age, he was hospitalized for treatment of Staphylococcus aureus cellulitis. Each infection responded well to short courses of antibiotic therapy. He has received all scheduled immunizations up to 12 months. Physical exam reveals a pale, thin child who is below the 3rd percentile for height and weight. He has normal features and developmental milestones. Further family history reveals a maternal uncle with similar symptoms in childhood. Immunologic work up is notable for severe hypogammaglobulinemia and low antibody vaccine titers. Genetic testing for BTK mutation confirms the diagnosis of X-Linked Agammaglobulinemia (XLA). Treatment with intravenous immunoglobulin replacement is started for management of antibody deficiency. Over the next 12 months, the boy has a significant decrease in infections and is noted to have improved growth.
Right middle lobe consolidation on chest x-ray on an infant with X-linked agammaglobulinemia. Blood culture from this infant grew Streptococcus pneumonia. (Used with permission from Camille Sabella, MD.)
Disorders of primary B cell immunodeficiency comprise approximately half of all primary immunodeficiencies. They are a group of heterogeneous disorders resulting from disruption of B cell maturation and function at various stages of development. The main role of B lymphocytes is production of antibodies for recognition and destruction of foreign antigens. Dysfunction of B lymphocytes results in impaired antibody production leading to illness characterized by unusual susceptibility to recurrent infections, particularly by encapsulated bacterial pathogens.
B cell immunodeficiencies are distinguished phenotypically by clinical severity, mode of inheritance, and age of onset. As a group, they share common clinical features and strategies for evaluation and management that will be discussed in this chapter.
Humoral immune deficiency.
Antibody deficiency syndrome.
X-Linked Agammaglobulinemia (XLA)/Bruton’s Agammaglobulinemia.
Common Variable Immunodeficiency (CVID).
Transient Hypogammaglobulinemia of Infancy.
Hyper IgM Syndrome.
B cell immunodeficiencies make up approximately 50 percent of primary immune deficiencies.1
IgA deficiency is the most common B cell disorder (estimated incidence of 1 in 700 persons of European ancestry).2
The second most common B cell disorder is CVID (estimated incidence of 1 in 30,000 ro 50,000 persons).3
Early B cell defects such as X-linked Agammaglobulinemia (XLA) are rare (estimated incidence of XLA is 1 per 200,000 male births).2
XLA accounts for ...
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