A case of Bruton's disease with normal immunoglobulin G level.

X-linked agamaglobulinemia (XLA) or Bruton’s disease is a genetic disease resulting from a mutation in the Bruton’s tyrosine kinase (Btk) gene. This mutation leads to B cell arrest during differentiation (1). This disease was first described by Ogden Bruton in 1952 (2). Approximately 85% of the affected subjects are male (3). This disorder is inherited as an X-linked recessive trait. Carrier females have no symptoms but have a 50% chance for transmission of the disorder to each of their sons. It is now possible to determine if the fetus of a carrier mother has XLA (4). The prevalence of the disease ranges from 1 in 10,000 to 1 in 50,000 (1). Half of the affected individuals are diagnosed during the first year of life and more than 90% of them are diagnosed up to fifth year (3). Diagnosis of the disease is suggested by lymphoid hypoplasia (minimal or no tonsillar tissue and no palpable lymph node) and total immunoglobulins level less than 100 mg/dl. Isohemagglutinins and antibodies to antigens given during routine immunization are abnormally low in this disorder as well. Flow cytometry is an important test for this diagnosis (5). Patients with XLA are protected for the first few months of life by maternal antibody and therefore do not typically present clinically with infection until after 6 months of age, when the maternally-derived antibody level decreases significantly. After diagnosis, treatment includes replacement of intravenous immunoglobulin (IVIG), which significantly reduces the risk of infection (6). The most common organisms affecting these patients are Haemophilus influenza, Streptococcus pneumonia and Staphylococcus aureus (3). Based on our knowledge, 4 cases of XLA patients with normal IgG levels (above 500 mg/dl) and 5 cases of XLA subjects with near normal IgG levels (400-500 mg/dl) have been reported in the world (7). Here, we report a case of Bruton’s disease as the fifth case with normal serum IgG level.