Primary asplenia is a rare condition with poorly known etiology. Mowat-Wilson 
syndrome (MWS) is characterized by typical facial dysmorphisms, intellectual 
disability, microcephaly, epilepsy and the possible presence of internal organ 
malformations. It is caused by heterozygous mutations or deletions in the ZEB2 
gene. Nearly 180 patients have been reported to date, but only one with 
asplenia. We report here spleen hypo/aplasia in 4 out of 6 MWS patients, with 
severe infectious complications for 3 of them. Our report shows that spleen 
hypo/aplasia is part of the MWS phenotype and makes ZEB2 a possible candidate 
gene for primary asplenia.