Infant with both<unk>  and anencephaly Genetics There are no known family ties in<unk>  and recurrence rates are extremely low. Not much is known about the exact mechanism involved in<unk> . It is hypothesized that like other developmental malformations, there are multiple origins for<unk> . Recent work has identified mutations in the hedgehog acyltransferase (HHAT) gene that have caused<unk>  along with holoprosencephaly and agnathia. The mutation in which causes this disease is a loss-of-function mutation. Before this discovery in 2010, HHAT was known to play a role in the sonic hedgehog pathway. When HHAT contains a loss-of-function mutation, less HHAT protein is produced. is necessary for the production of Hedgehog () proteins post-transcriptionally. As HHAT production decreases, production of long-range Hh proteins decreases proportionally. production disturb the production of extracellular signal-regulated kinases, bone morphogenetic proteins, and fibroblast growth factors, all of which play important roles in craniofacial patterning. Disruption of these pathways leads to abnormal bone and cartilage formation causing<unk>  and multiple other craniofacial patterning problems. Genetic counseling Little genetic counseling can be offered for<unk>  because the genetic origins are not fully understood. In order to make genetic counseling for families easier this disease is often differentially diagnosed with other diseases that can occur at the same time such as anencephaly and acalvaria, though these diseases may not always occur simultaneously. Reoccurrence rates are extremely low, so genetic counseling is not always necessary. Amniotic band syndrome During amniotic band syndrome (ABS), fibrous bands may entrap various parts of the developing fetus causing malformations. When these fibrous bands form around the developing skull, the bones will not form properly. ABS occurring in the developing brain neural tissue is one cause of<unk> . When is the cause of<unk>  the fibrous bands cannot be detected through ultrasound.
Acrania
Macrodontia 
Macrotia
Microcoria
Spotted lunulae
Amastia
Macrostomia
Polycephaly