Another Fanconi anemia gene joins the club.

Fanconi anemia (FA) is the most common inherited bone marrow failure disorder, caused by pathogenic variants in genes involved in the FA DNA repair pathway. In this issue of the JCI, two studies report three germline homozygous loss-of-function variants in FAAP100, a key component of the FA core complex, identified in three unrelated families. These variants result in severe developmental phenotypes that are among the most extreme reported in FA to date. Harrison et al. described individuals from two families with recurrent pregnancy loss and neonatal death due to homozygous FAAP100 frameshift and truncating variants, respectively. Kuehl et al. identified a homozygous missense variant in a fetus with congenital malformations consistent with FA. Collectively, both studies provide robust functional evidence from ex vivo and in vitro assays with animal models supporting the pathogenicity of these variants and establish FAAP100 as a causative FA gene.