Definition:

Immunodeficiency, centromeric instability, facial anomaly syndrome (ICF syndrome) is a rare autosomal recessive syndrome associated with mutations in the DNA methyltransferase 3B gene (DNMT3B) in 75% of cases. Patients have variable hypogammaglobulinemia but typically have profound reduction or absence of two or more Ig isotypes. This leads to severe immunodeficiency and death due to infection often before adulthood. Deficiencies of B-cell receptors are caused by mutations in the genes that encode immunoglobulin heavy or light chains or their associated signaling molecules, leading to agammaglobulinemia or hypogammaglobulinemia. Mutations in immunoglobulin heavy-chain genes (such as gamma1, 2, 3, or 4; alpha1 or 2; and epsilon) cause deficiencies of individual classes or subclasses of immunoglobulins, but circulating B cells are present and overall antibody function is usually normal. Mutations in the kappa light-chain gene result in a population of immunoglobulin molecules with only lambda light chains instead of the usual mixture of kappa and lambda types.