The incidence is estimated to range from 0.1–1.2 per 10,000 live births, though the true incidence is unknown. As of 2005, the highest prevalence was found in Canada and estimated at 1 in 8,500 live births.

In a newborn boy thought to have Fryns syndrome, Clark and Fenner-Gonzales (1989) found mosaicism for a tandem duplication of 1q24-q31.2. They suggested that the gene for this disorder is located in that region. However, de Jong et al. (1989), Krassikoff and Sekhon (1990), and Dean et al. (1991) found possible Fryns syndrome associated with anomalies of chromosome 15, chromosome 6, chromosome 8(human)and chromosome 22, respectively. Thus, these cases may all represent mimics of the mendelian syndrome and have no significance as to the location of the gene for the recessive disorder.

By array CGH, Slavotinek et al. (2005) screened patients with DIH and additional phenotypic anomalies consistent with Fryns syndrome for cryptic chromosomal aberrations. They identified submicroscopic chromosome deletions in 3 probands who had previously been diagnosed with Fryns syndrome and had normal karyotyping with G-banded chromosome analysis. Two female infants were found to have microdeletions involving 15q26.2 (see 142340), and 1 male infant had a deletion in band 8p23.1 (see 222400).

In France, Aymé, "et al." (1989) estimated the prevalence of Fryns syndrome to be 0.7 per 10,000 births based on the diagnosis of 6 cases in a series of 112,276 consecutive births (live births and perinatal deaths).

Currently, research is focusing on identifying the role of the genes on 18p in causing the signs and symptoms associated with deletions of 18p. This will ultimately enable predictive genotyping.

TGIF-Mutations and deletions of this gene have been associated with holoprosencephaly. Penetrance is incomplete, meaning that a deletion of one copy of this gene is not in and of itself sufficient to cause holoprosencephaly. Ten to fifteen percent of people with 18p- have holoprosencephaly, suggesting that other genetic and environmental facts play a role in the etiology of holoprosencephaly in these individuals.

SHORT syndrome is a medical condition in which affected individuals have multiple birth defects in different organ systems.

It was characterized in 1975.

Ethmocephaly is a type of cephalic disorder caused by holoprosencephaly. Ethmocephaly is the least common facial anomaly. It consists of a proboscis separating narrow-set eyes with an absent nose and microphthalmia (abnormal smallness of one or both eyes). Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril situated below incomplete or underdeveloped closely set eyes.

The least severe in the spectrum of facial anomalies is the median cleft lip, also called premaxillary agenesis.

Although the causes of most cases of holoprosencephaly remain unknown, some may be due to dominant or chromosome causes. Such chromosomal anomalies as trisomy 13 and trisomy 18 have been found in association with holoprosencephaly, or other neural tube defects. Genetic counseling and genetic testing, such as amniocentesis, is usually offered during a pregnancy if holoprosencephaly is detected. The recurrence risk depends on the underlying cause. If no cause is identified and the fetal chromosomes are normal, the chance to have another pregnancy affected with holoprosencephaly is about 6%.

There is no treatment for holoprosencephaly and the prognosis for individuals with the disorder is poor. Most of those who survive show no significant developmental gains. For children who survive, treatment is symptomatic. It is possible that improved management of diabetic pregnancies may help prevent holoprosencephaly, however there is no means of primary prevention.

Microlissencephaly is listed in Orphanet database as a rare disease. There is no much information available about the epidemiology of microlissencepahly in literature. A PhD thesis has estimated the prevalence of microlissencepahly in South–Eastern Hungary between July 1992 and June 2006 to be a case every 91,000 live births (0.11:10,000).

CHARGE syndrome was formerly referred to as CHARGE association, which indicates a non-random pattern of congenital anomalies that occurs together more frequently than one would expect on the basis of chance. Very few people with CHARGE will have 100% of its known features. In 2004, mutations on the CHD7 gene (located on Chromosome 8) were found in 10 of 17 patients in the Netherlands, making CHARGE an official syndrome. A US study of 110 individuals with CHARGE syndrome showed that 60% of those tested had a mutation of the CHD7 gene.

In 2010, a review of 379 clinically diagnosed cases of CHARGE syndrome, in which CHD7 mutation testing was undertaken found that 67% of cases were due to a CHD7 mutation. CHD7 is a member of the chromodomain helicase DNA-binding (CHD) protein family that plays a role in transcription regulation by chromatin remodeling.

The incidence of Fraser syndrome is 0.043 per 10,000 live born infants and 1.1 in 10,000 stillbirths, making it a rare syndrome.

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Say–Neger syndrome is a rare X-linked genetic disorder that is mostly characterized as developmental delay. It is one of the rare causes of short stature. It is closely related with trigonocephaly (a misshapen forehead due to premature fusion of bones in the skull). People with Say–Meyer syndrome have impaired growth, deficits in motor skills development and mental state.

It is suggested that it is from a X-linked transmission.

it is mainly associated with talon cusp. It is developmental anomaly of shape of teeth

As a recessive genetic condition, both parents must carry the asymptomatic gene and pass it along to their child, a chance of 25 percent. Despite determination of cause, hydranencephaly afflicts both males and females in equal numbers.

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

SHORT is an acronym for short stature, hyperextensibility of joints and/or inguinal hernia, ocular depression, rieger anomaly and teething delay.

Other characteristics common in SHORT syndrome are a triangular face, small chin with a dimple, a loss of fat under the skin (lipodystrophy), abnormal position of the ears, hearing loss and delayed speech.

These lesions usually present in neonates, although they may not come to clinical attention until adulthood (for cosmetic reasons). There is no gender predilection. They are present in approximately 3-6 per 1000 live births.

Microlissencephaly (MLIS) is a rare congenital brain disorder that combines severe microcephaly (small head) with lissencephaly (smooth brain surface due to absent sulci and gyri). Microlissencephaly is a heterogeneous disorder i.e. it has many different causes and a variable clinical course. Microlissencephaly is a malformation of cortical development (MCD) that occurs due to failure of neuronal migration between the third and fifth month of gestation as well as stem cell population abnormalities. Numerous genes have been found to be associated with microlissencephaly, however, the pathophysiology is still not completely understood.

The combination of lissencephaly with severe congenital microcephaly is designated as microlissencephaly only when the cortex is abnormally thick. If such combination exists with a normal cortical thickness (2.5 to 3 mm), it is known as "microcephaly with simplified gyral pattern" (MSGP). Both MLIS and MSGP have a much more severe clinical course than microcephaly alone. They are inherited in autosomal recessive manner. Prior to 2000, the term “microlissencephaly” was used to designate both MLIS and MSGP.

Although it is possible for the birthmark and atrophy in the cerebral cortex to be present without symptoms, most infants will develop convulsive seizures during their first year of life. There is a greater likelihood of intellectual impairment when seizures are resistant to treatment. Studies do not support the widely held belief that seizure frequency early in life in patients who have SWS is a prognostic indicator.

Edwards syndrome occurs in about one in 5,000 live births, but more conceptions are affected by the syndrome because the majority of those diagnosed with the condition prenatally will not survive to birth. Although women in their 20s and early 30s may conceive babies with Edwards syndrome, the risk of conceiving a child with it increases with a woman's age. The average maternal age for conceiving a child with this disorder is 32½.

Rubinstein–Taybi syndrome (RTS), also known as broad thumb-hallux syndrome or Rubinstein syndrome, is a condition characterized by short stature, moderate to severe learning difficulties, distinctive facial features, and broad thumbs and first toes. Other features of the disorder vary among affected individuals.

People with this condition have an increased risk of developing noncancerous and cancerous tumors, leukemia, and lymphoma. This condition is sometimes inherited as an autosomal dominant pattern and is uncommon, many times it occurs as a de novo (not inherited) occurrence, it occurs in an estimated 1 in 125,000-300,000 births.

Fleischer's syndrome is an extremely rare congenital anomaly characterized by displacement of the nipples, occasional polymastia, and hypoplasia of both kidneys.

Cebocephaly [Greek "kebos", monkey + "kephale", head] is a developmental anomaly of the head characterized by a monkey-like head, with a defective small, flattened nose with a single nostril or absent nose and closely set eyes. Cebocephaly is part of a group of defects called holoprosencephaly. The incidence of cebocephaly is 1 in 16,000 births.

The growth retardation dates from the intrauterine period (development in the uterus.) The long-term developmental growth and outcome is not known, but the early childhood development is known, which is said to be moderately delayed. Craniosynostosis is usually rare among the X-Linked Intellectual Disability Syndromes, but when it is present, it affects the metopic structure (forehead).

The molecular genetics of Axenfeld syndrome are poorly understood, but centers on three genes identified by cloning of chromosomal breakpoints from patients.

This disorder is inheritable as an autosomal dominant trait, which means the defective gene is located on an autosome, and only one copy of the gene is sufficient to cause the disorder when inherited from a parent who has the disorder. As shown in the diagram, this gives a 50/50 chance of offspring inheriting the condition from an affected parent.

Known environmental factors include certain infections during pregnancy such as Rubella, drugs (alcohol, hydantoin, lithium and thalidomide) and maternal illness (diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).

Being overweight or obese increases the risk of congenital heart disease. Additionally, as maternal obesity increases, the risk of heart defects also increases. A distinct physiological mechanism has not been identified to explain the link between maternal obesity and CHD, but both prepregnancy folate deficiency and diabetes have been implicated in some studies.