Here we report five patients from four unrelated families presenting with neurodevelopmental delay, dysmorphic features, brain structural abnormalities with or without growth restriction, hypotonia, and microcephaly, all of whom are homozygous for extremely rare and predicted loss-of-function (pLoF) or missense variants in WSB2, inherited from consanguineous parents. This evidence concerns the gene WSB2 and microcephaly.