Comparison of holoprosencephaly (HPE) type distribution among the three ‘classic’ HPE types for the patients with intragenic ZIC2 mutations, as well as two sources from the literature and a source obtained from our database: Lazaro et al (2004) described a cohort of both living patients and deceased fetuses with non-chromosomal, non-syndromic HPE, while Orioli et al (2007) describes a cohort of patients born with HPE.7 8 We also compare our cohort of patients with mutations in ZIC2 with a cohort of prospectively ascertained probands with non-chromosomal, non-syndromic HPE whose samples were sent to the National Institutes of Health (NIH) over approximately a 3 year period. Due to low prevalence, middle interhemispheric variant (MIHV) was not considered
| Intragenic ZIC2 mutations n (%) | Lazaro et al7 n (%) | Orioli and Castilla8 n (%) | NIH n (%) | |
| Alobar | 28 (32) | 15 (22) | 33 (40) | 10 (13) |
| Semilobar | 48 (55) | 31 (45) | 36 (43) | 45 (6) |
| Lobar | 11 (13) | 23 (33) | 14 (17) | 20 (27) |
| Total | 87 | 69 | 83 | 75 |
| Comparison vs ZIC2 cohort | χ2(2)=9.88, p=0.0077 | χ2(2)=2.39, p=0.30 | χ2(2)=10.4, p=0.0055 |