TRNT1 and congenital sideroblastic anemia-B-cell immunodeficiency-periodic fever-developmental delay syndrome: Sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD) is a serious autosomal recessive syndrome caused by biallelic mutations in cytosine-cytosine-adenosine tRNA nucleotidyltransferase 1 (<i>TRNT1</i>).