Holoprosencephaly is a clinically and genetically heterogeneous midline brain 
malformation associated with neurologic manifestations including developmental 
delay, intellectual disability and seizures. Although mutations in the sonic 
hedgehog gene SHH and more than 10 other genes are known to cause 
holoprosencephaly, many patients remain without a molecular diagnosis. Here we 
show that a homozygous truncating mutation of STIL not only causes severe 
autosomal recessive microcephaly, but also lobar holoprosencephaly in an 
extended consanguineous Pakistani family. STIL mutations have previously been 
linked to centrosomal defects in primary microcephaly at the MCPH7 locus. Our 
results thus expand the clinical phenotypes associated with biallellic STIL 
mutations to include holoprosencephaly.