B-cell immunodeficiency appears to be a consistent feature of TRNT1 deficiency, which is sometimes known by the acronym SIFD, for sideroblastic anaemia, immunodeficiency, fever and developmental delay. This condition is characterised by recurrent debilitating episodes of severe fever. This evidence concerns the gene TRNT1 and congenital sideroblastic anemia-B-cell immunodeficiency-periodic fever-developmental delay syndrome.