Two cases of neonatal group B streptococcal (GBS) infection occurring in a large consanguineous kindred are described. The observation suggests that susceptibility to isolated GBS disease in this family may have been the result of an inborn error of immunity inherited as a Mendelian autosomal recessive trait. (C) 2016 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license.