Comparison of the incidence of phenotype features of selected conditions in which holoprosencephaly is common from literature review*
| Our cases† | Smith-Lemli-Opitz syndrome | Young-Madders syndrome | Trisomy 13 | SHH mutation phenotype | |
| Mode of inheritance | Recessive | Recessive | Recessive | Sporadic dominant | Autosomal dominant |
| Holoprosencephaly (%) | 4/4 | 5 | 100‡ | 30 | 36 |
| Characteristic facies (%) | >90 | >90 | >90 | 60 | >60 |
| Cleft lip (%) | 3/4 | 40 | 53 | 40 | 20 |
| Congenital heart disease (%) | 3/4 | 50 | 15 | 80 | 2 |
| Microcephaly (%) | 1/4 | 80% | 12 | 20 | 10 |
| Male ambiguous genitalia (%) | 0/2 | 50 | 60 | 0 | 5 |
| Intellectual deficit range (%) | 4/4 severe | Normal (>5%) to severe | 100% severe | 100% severe | Normal (30%) to severe |
| Postaxial polydactyly (%) | 0/4 | 33 | 90‡ | 80 | <10 |
| 2/3 toe syndactyly (%) | 0/4 | >90 | 10§ | 0§ | 0§ |
*From the references in the text.
†As we describe four cases, we give numbers not a percentage.
‡Presumably a bias introduced by the disease definition.
§Presumably under-reported.
SHH, sonic hedgehog.