B-cell deficiency identified by newborn screening

Abstract

 Newborn screening（NBS）is carried out at public expense for approximately 20 diseases in Japan; however, each prefecture independently conducts additional NBS including several more diseases. Miyazaki Prefecture has optionally included inborn errors of immunity（IEIs）and lysosomal storage diseases since April 2020. We herein report a baby who suffered from B-cell deficiency（BCD）that was identified by NBS conducted in Miyazaki Prefecture. The baby had low levels of kappa-deleting recombination excision circles（KRECs）and was referred to our hospital. Several measurements of CD19-positive B cells in the peripheral blood consistently showed values <2%, leading to the diagnosis of BCD. Periodic immunoglobulin replacement successfully led to a healthy outcome without serious infection developing over a period of more than 17 months. This is the first case of BCD identified by NBS and that underwent prophylactic gamma globulin replacement in Japan. Severe combined immunodeficiency disease and BCD are IEIs known to cause severe sequelae, and patients sometimes die without a correct diagnosis being made; therefore, their early diagnosis and early treatment are extremely important. The inclusion of IEIs in NBS has proven to be cost-effective all over the world. In the future, it is expected that IEIs will be covered by NBS public funds in Japan as well.