TRNT1 and Immunodeficiency: Congenital sideroblastic anemia-B-cell immunodeficiency-periodic fever-developmental delay syndrome (SIFD) is a form of congenital SA associated with immunodeficiency, periodic fevers, and developmental delay caused by a loss of function mutation in the TRNT1 gene coding for tRNA nucleotidyl transferase 1 involved in the maturation of cytosolic and mitochondrial transfer RNA.