In some cases, the defect is linked to mutations of the EMX2, SIX3, and Collagen, type IV, alpha 1 genes. Because having a sibling with schizencephaly has been statistically shown to increase risk of the disorder, it is possible that there is a heritable genetic component to the disease.

In utero exposure to cocaine and other street drugs can lead to septo-optic dysplasia.

Rare familial recurrence has been reported, suggesting at least one genetic form (HESX1). In addition to HESX1, mutations in OTX2, SOX2 and PAX6 have been implicated in de Morsier syndrome, but in most cases SOD is a sporadic birth defect of unknown cause and does not recur with subsequent pregnancies.

Recent research has found that Dandy–Walker syndrome often occurs in patients with PHACES syndrome.

The causes for PWS are either genetic or unknown. Some cases are a direct result of the RASA1 gene mutations. And individuals with RASA1 can be identified because this genetic mutation always causes multiple capillary malformations. PWS displays an autosomal dominant pattern of inheritance. This means that one copy of the damaged or altered gene is sufficient to elicit PWS disorder. In most cases, PWS can occur in people that have no family history of the condition. In such cases the mutation is sporadic. And for patients with PWS with the absence of multiple capillary mutations, the causes are unknown.

According to Boston’s Children Hospital, no known food, medications or drugs can cause PWS during pregnancy. PWS is not transmitted from person to person. But it can run in families and can be inherited. PWS effects both males and females equally and as of now no racial predominance is found

At the moment, there are no known measures that can be taken in order to prevent the onset of the disorder. But Genetic Testing Registry can be great resource for patients with PWS as it provides information of possible genetic tests that could be done to see if the patient has the necessary mutations. If PWS is sporadic or does not have RASA1 mutation then genetic testing will not work and there is not a way to prevent the onset of PWS.

In utero exposure to cocaine and other street drugs can lead to schizencephaly.

There are approximately three hundred known cases of Carpenter Syndrome in the United States. Only 1 in 1 million live births will result in an infant affected by Carpenter Syndrome (RN, 2007).

Carpenter Syndrome is an autosomal recessive disease which means both parents must have the faulty genes in order to pass the disease onto their children. Even if both parents possess the faulty gene there is still only a twenty five percent chance that they will produce a child affected by the syndrome. Their children who do not have the disease will still be carriers and possess the ability to pass the disease onto their offspring if their spouse is also a carrier of the particular gene.

Until recently, the medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause (genotype) despite the widely varying set of medical characteristics (phenotype) that are clinically visible in the disorders. Dandy–Walker syndrome is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel-Gruber syndrome and some forms of retinal degeneration.

Genetic associations of the condition are being investigated.

Prognosis varies widely depending on severity of symptoms, degree of intellectual impairment, and associated complications. Because the syndrome is rare and so newly identified, there are no long term studies.

Mosaic mutations in PIK3CA have been found to be the genetic cause of M-CM. Genetic testing for the mutation is currently only available on a research basis. Other overgrowth conditions with distinct phenotypes have also been found to be caused by mosaic mutations in PIK3CA. How different mutations in this gene result in a variety of defined clinical syndromes is still being clarified. Mutations in PIK3CA have not been found in a non-mosaic state in any of these disorders, so it is unlikely that the conditions could be inherited.

Limb body wall complex (LBWC) is a rare fetal malformation of unknown origins.

Traditionally diagnosis has been based on the Van Allen et al., criteria, i.e. the presence of two out of three of the following anomalies:

1. Exencephaly or encephalocele with facial clefts

2. Thoraco and or abdominoschisis and

3. Limb defects.

LBWC occurs in approximately 0.32 in 100,000 births.

At this time, there is no known cause of Limb Body Wall Complex. However, there have been tentative links made between a diagnosis of LBWC and cocaine use. In addition, current research has shown that there may be a genetic cause for a small limited number of LBWC cases.

Limb Body Wall Complex is a lethal birth defect. There are only anecdotal stories of survivors.

The actual incidence of this disease is not known, but only 243 cases have been reported in the scientific literature, suggesting an incidence of on the order of one affected person in ten million people.

In utero exposure to cocaine and other street drugs can lead to agenesis of corpus callosum.

The reported incidence of constriction ring syndrome varies from 1/1200 and 1/15000 live births. The prevalence is equally in male and female.

Fetomaternal factors like prematurity, maternal illnes, low birth weight and maternal drug exposure are predisposing factors for the constriction ring syndrome.

No positive relationship between CRS and genetic inheritance has been reported.

Craniofrontonasal dysplasia is a very rare genetic condition. As such there is little information and no consensus in the published literature regarding the epidemiological statistics.

The incidence values that were reported ranged from 1:100,000 to 1:120,000.

Imperforate anus has an estimated incidence of 1 in 5000 births. It affects boys and girls with similar frequency. However, imperforate anus will present as the low version 90% of the time in females and 50% of the time in males.

Imperforate anus is an occasional complication of sacrococcygeal teratoma.

Minor physical anomalies (MPAs) are relatively minor (typically painless and, in themselves, harmless) congenital physical abnormalities consisting of features such as low-set ears, single transverse palmar crease, telecanthus, micrognathism, macrocephaly, hypotonia and furrowed tongue. While MPAs may have a genetic basis, they might also be caused by factors in the fetal environment: anoxia, bleeding, or infection. MPAs have been linked to disorders of pregnancy and are thought by some to be a marker for insults to the fetal neural development towards the end of the first trimester. Thus, in the neurodevelopmental literature, they are seen as indirect indications of inferferences with brain development.

MPAs have been studied in autism, Down syndrome, and in schizophrenia. A 2008 meta-analysis found that MPAs are significantly increased in the autistic population. A 1998 study found that 60% of its schizophrenic sample and 38% of their siblings had 6 or more MPAs (especially in the craniofacial area), while only 5% of the control group showed that many.

The most often cited MPA, high arched palate, is described in articles as a microform of a cleft palate. Cleft palates are partly attributable to hypoxia. The vaulted palate caused by nasal obstruction and consequent mouth breathing, without the lateralising effect of the tongue, can produce hypoxia at night.

Other MPAs are reported only sporadically. Capillary malformation is induced by RASA1 mutation and can be changed by hypoxia. A study in the American Journal of Psychiatry by Trixler et al.: found hemangiomas to be highly significant in schizophrenia. Exotropia is reported as having low correlation and high significance as well. It can be caused by perinatal hypoxia.

A few studies have worked on providing details related to the outlook of disease progression. Two studies show that each year 0.5% of people who have never had bleeding from their brain cavernoma, but had symptoms of seizures, were affected by bleeding. In contrast, patients who have had bleeding from their brain cavernoma in the past had a higher risk of being affected by subsequent bleeding. The statistics for this are very broad, ranging from 4%-23% a year. Additional studies suggest that women and patients under the age of 40 are at higher risk of bleeding, but similar conducted studies did not reach the same conclusion. However, when cavernous hemangiomas are completely excised, there is very little risk of growth or rebleeding. In terms of life expectancy, not enough data has been collected on patients with this malformation in order to provide a representative statistical analysis.

The most widely accepted pathophysiological mechanism by which Chiari type I malformations occur is by a reduction or lack of development of the posterior fossa as a result of congenital or acquired disorders. Congenital causes include hydrocephalus, craniosynostosis (especially of the lambdoid suture), hyperostosis (such as craniometaphyseal dysplasia, osteopetrosis, erythroid hyperplasia), X-linked vitamin D-resistant rickets, and neurofibromatosis type I. Acquired disorders include space occupying lesions due to one of several potential causes ranging from brain tumors to hematomas.

Head trauma may cause cerebellar tonsillar ectopia, possibly because of dural strain. Additionally, ectopia may be present but asymptomatic until whiplash causes it to become symptomatic. Posterior fossa hypoplasia causes reduced cerebral and spinal compliance.

The prevalence of congenital Chiari I malformation, defined as tonsilar herniations of 3 to 5 mm or greater, was previously believed to be in the range of one per 1000 births, but is likely much higher. Women are three times more likely than men to have a congenital Chiari malformation. Type II malformations are more prevalent in people of Celtic descent. A study using upright MRI found cerebellar tonsillar ectopia in 23% of adults with headache from motor-vehicle-accident head trauma. Upright MRI was more than twice as sensitive as standard MRI, likely because gravity affects cerebellar position.

Cases of congenital Chiari malformation may be explained by evolutionary and genetic factors. Typically, an infant's brain weighs around 400g at birth and triples to 1100-1400g by age 11. At the same time the cranium triples in volume from 500 cm to 1500 cm to accommodate the growing brain. During human evolution, the skull underwent numerous changes to accommodate the growing brain. The evolutionary changes included increased size and shape of the skull, decreased basal angle and basicranial length. These modifications resulted in significant reduction of the size of the posterior fossa in modern humans. In normal adults, the posterior fossa comprises 27% of the total intracranial space, while in adults with Chiari Type I, it is only 21%. If a modern brain is paired with a less modern skull, the posterior fossa may be too small, so that the only place where the cerebellum can expand is the foramen magnum, leading to development of Chiari Type I. H. neanderthalensis had platycephalic (flattened) skull. Some cases of Chiari are associated with platybasia (flattening of the skull base).

Until recently, the medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause despite the widely varying symptoms apparent on clinical examination. Agenesis of the corpus callosum is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell organelles that are present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet–Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alström syndrome, Meckel–Gruber syndrome, and some forms of retinal degeneration.

Davis and Barry 1977 tested allele frequencies in domestic cats. Among the 265 cats observed, there were 101 males and 164 females. Only one cat was recorded to have the ectrodactyly abnormality, illustrating this rare disease.

According to M.P. Ferreira, a case of ectrodactyly was found in a two-month-old male mixed Terrier dog. In another study, Carrig and co-workers also reported a series of 14 dogs with this abnormality proving that although ectrodactyly is an uncommon occurrence for dogs, it is not entirely unheard of.

a combination of various vascular malformations. They are 'complex' because they involve a combination of two different types of vessels.

- CVM: capillary venous malformation

- CLM: capillary lymphatic malformation

- LVM: lymphatic venous malformation

- CLVM: capillary lymphatic venous malformation. CLVM is associated with Klippel-Trenaunay syndrome

- AVM-LM: Arteriovenous malformation- lymphatic malformation

- CM-AVM: capillary malformation- arteriovenous malformation

Carpenter syndrome has been associated with mutations in the RAB23 gene, which is located on chromosome 6 in humans. Additionally, three key SNPs in the MEGF8 gene, located on chromosome 19 at 19q13.2, have been identified as primary causes of Carpenter syndrome.

In a study performed by the Department of Forestry and Natural Resources at Purdue University, approximately 2000 salamanders (687 adults and 1259 larvae) were captured from a large wetland complex and evaluated for malformations. Among the 687 adults, 54 (7.9%) were malformed. Of these 54 adults, 46 (85%) had missing (ectrodactyly), extra (polyphalangy) or dwarfed digits (brachydactyly). Among the 1259 larvae, 102 were malformed, with 94 (92%) of the malformations involving ectrodactyly, polyphalangy, and brachydactyly. Results showed few differences in the frequency of malformations among life-history changes, suggesting that malformed larvae do not suffer substantially higher mortality than their adult conspecifics.