In addition, postnatal HF defects leading to alopecia have been reported for both RAC1 and CDC42 (Castilho et al., 2007; Chrostek et al., 2006; Wu et al., 2006a; Behrendt et al., 2012), and for CDC42, defects in basement membrane assembly, hair differentiation and WNT signaling have also been described (Wu et al., 2006b; Wu et al., 2006a). Here, RAC1 is linked to hydrops fetalis.