Review Question - QID 213240

This boy who is developing multiple systemic infections at a young age and has universally decreased B-cell function most likely has Bruton agammaglobulinemia, which is caused by a mutation in a tyrosine kinase, which phosphorylates proteins.

Bruton agammaglobulinemia is a primary humoral immunodeficiency that is characterized by decreased immunoglobulin production in all lines (IgM, IgG, and IgA). It is caused by an X-linked recessive defect in Bruton tyrosine kinase, which is important in phosphorylating proteins during the B-cell maturation pathway. Without this critical kinase, there is impaired signaling from the pre-B-cell receptor, which leads to defective development and premature death of B-cells. The impairment in this response will lead to recurrent childhood infections.

Incorrect Answers:
Answer 1: Actin polymerization is consistent with the activity of the WASp protein that is mutated in Wiskott-Aldrich syndrome; however, this disease would present with eczema and thrombocytopenia.

Answer 2: Autoimmune regulation is consistent with the activity of the AIRE protein that is mutated in chronic mucocutaneous candidiasis; however, this disease would present with thrush and diaper rash.

Answer 3: Lysosomal trafficking is consistent with the activity of the LYST gene that is mutated in Chediak-Higashi syndrome; however, this disease would present with partial albinism and pancytopenia.

Answer 4: Nucleotide salvage is consistent with the activity of the adenosine deaminase protein that is mutated in severe combined immunodeficiency syndrome; however, this disease would present with decreased CD4 positive T cells as well.

Bullet Summary:
Bruton agammaglobulinemia is an autoimmune disease that is caused by a mutation in the Bruton tyrosine kinase.