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.

Perlman syndrome is a rare disease with an estimated incidence of less than 1 in 1,000,000. As of 2008, less than 30 patients had ever been reported in the world literature.

Research on the risk for developing schizophrenia in Ashkenazi Jews and other populations showed that 3q29 microdeletion syndrome leads to a significant higher rate of schizophrenia.

By 1990, 65 patients had been reported in the literature, with no sex or ethnic preference notable. Some individuals present with minimal malformation; rarely patients have died during infancy as a result of severe central nervous system involvement or respiratory complications. Several syndromes are related to the Freeman–Sheldon syndrome spectrum, but more information is required before undertaking such nosological delineation.

Weissenbacher-Zweymüller syndrome affects males and females in the same numbers. About 30 cases have been reported in medical literature. This disorder can be underdiagnosed causing no true frequency in the population. Only 30 cases have been reported in medical literature.

The minimal deletion causing this syndrome has been defined as a 3 megabase region that contains the genes GPR35, GPC1 and STK25.

Almost all deletions are found to be terminal deletions at the end of chromosome 2. There is a high frequency of "de novo" deletions, but multiple cases within a single family are also observed. Equal proportions of maternally and paternally derived rearrangements were seen in Aldred's series. No common breakpoints for the deletion were identified indicating that the 2q37 rearrangement is unlikely to be mediated by non-homologous recombination and low-copy repeats. In a study of 20 patients, no clear relationship was found between clinical features and the size or position of the monosomic region.

Young–Simpson syndrome (YSS) is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, mental retardation and postnatal growth retardation.

Other symptoms include transient hypothyroidism, macular degeneration and torticollis. The condition was discovered in 1987 and the name arose from the individuals who first reported the syndrome. An individual with

YSS has been identified with having symptoms to a similar syndrome known as Ohdo Blepharophimosis syndrome, showing that it is quite difficult to diagnose the correct condition based on the symptoms present. Some doctors therefore consider these syndromes to be the same.

The mode of inheritance has had mixed findings based on studies undertaken. One study showed that the parents of an individual with YSS are unrelated and phenotypically normal, indicating a sporadic mutation, thus making it difficult to base the cause of the condition on genetic makeup alone. However, another study was done of an individual with YSS who had first cousins as parents, giving the possibility of autosomal recessive inheritance.

There are little data on prognosis. Rarely, some patients have died in infancy from respiratory failure; otherwise, life expectancy is considered to be normal.

Aglossia (aglossia congenita) is a congenital defect resulting in a partial development or complete absence of a tongue.

Aglossiais commonly associated with craniofacial and limb defects (Adactylia syndrome) and is thought to belong to a family of oromandibular limb hypogenesis syndrome or OLHS. It is believed to be caused by heat-induced vascular disruption near the fourth week of embryonic development.

The first known case was reported in the early 18th century by a member of the prominent De Jussieu family in France and cases to this day remain rare.

Gillespie syndrome, also called aniridia, cerebellar ataxia and mental deficiency. is a rare genetic disorder. The disorder is characterized by partial aniridia (meaning that part of the iris is missing), ataxia (motor and coordination problems), and, in most cases, intellectual disability. It is heterogeneous, inherited in either an autosomal dominant or autosomal recessive manner. Gillespie syndrome was first described by American ophthalmologist Fredrick Gillespie in 1965.

Nicolaides–Baraitser syndrome (NCBRS) is a rare genetic condition caused by de novo missense mutations in the SMARCA2 gene and has only been reported in less than 100 cases worldwide. NCBRS is a distinct condition and well recognizable once the symptoms have been identified.

Almost all patients with this syndrome have some degree of mental retardation and facial dysmorphism (round face, deep-set eyes, thin upper lip). Behavioural problems are common. Brachymetaphalangism (metacarpal or metatarsal shortening) is reported in ~50% of cases overall, but is typically not evident below the age of 2 years. There is striking phenotypic variability, and the size and extent of the deleted region cannot be used as accurate predictors of prognosis. Some patients have additional problems such as congenital heart disease and seizures.

Dominant genetic disorders can be caused by just a single copy of an abnormal gene. This abnormal gene can be the result of being inherited from either parent or be a new mutation. Most cases are caused by a de novo (new) mutation in the gene that occurs during the formation of the egg or sperm. These cases occur when there is no history of the disorder in the family.

The COL11A2 gene is responsible for providing instructions on making one component of the type XI collagen. Type XI collagen is a complex molecule that helps give structure and strength to the connective tissues. Collagen is found in bone. It is also found in cartilage that makes up most of the skeleton during early development. The mutation of COL11A2 in Weissenbacher-Zweymüller syndrome disrupts the assembly of the type XI collagen molecules. The malfunctioning collagen weakens the connective tissue causing impaired bone development.

COL11A2 is also associated with autosomal dominant non-syndromic hearing loss (ADNSHL). All mutations of COL11A2 in ADNSHL are missense mutations.

The condition was first described in 1978 by Pitt and Hopkins in two unrelated patients.

The genetic cause of this disorder was described in 2007. This disorder is due to a haploinsufficiency of the transcription factor 4 (TCF4) gene which is located on the long arm of chromosome 18 (18q21.2) The mutational spectrum appears to be 40% point mutations, 30% small deletions/insertions and 30% deletions. All appear to be "de novo" mutations and to date no risk factors have been identified.

A Pitt–Hopkins like phenotype has been assigned to autosomal recessive mutations of the contactin associated protein like 2 (CNTNAP2) gene on the long arm of chromosome 7 (7q33-q36) and the neurexin 1 alpha (NRXN1) gene on the short arm of chromosome 2 (2p16.3).

The true prevalence of PMS has not been determined. More than 1200 people have been identified worldwide according the Phelan-McDermid Syndrome Foundation. However, it is believed to be underdiagnosed due to inadequate genetic testing and lack of specific clinical features. It is known to occur with equal frequency in males and females. Studies using chromosomal microarray for diagnosis indicate that at least 0.5% of cases of ASD can be explained by mutations or deletions in the "SHANK3" gene. In addition when ASD is associated with ID, "SHANK3" mutations or deletions have been found in up to 2% of individuals.

In 2011, it was demonstrated that "de novo" mutations in the gene KAT6B caused YSS.

The incidence rate of ATR-16 syndrome is not easy to estimate and it is thought to be underdiagnosed. Scientists have described more than 20 cases as of 2013.

The estimated prevalence of Jacobsen syndrome is believed to be approximately 1 out of every 100,000 births. For reasons unknown females are twice as likely to have Jacobsen Syndrome than males. No preference for any race or ethnicity has been reported so far.

Minor degrees of curvature are common. Reports of incidence vary between 1% and 19.5%.

Bohring–Opitz syndrome (BOS) is a medical syndrome caused by a mutation in the ASXL1 gene. It is diagnosed by genetic testing and is characterised by characteristic craniofacial appearance, fixed contractures of the upper limbs, abnormal posture, feeding difficulties, intellectual disability, small size at birth, and failure to thrive. Some of these features are shared with other genetic syndromes.

Genetically, de novo truncating mutations in ASXL1 have been shown to account for approximately 50% of Bohring–Opitz syndrome cases.

The syndrome is extremely rare, with fewer than 80 known cases worldwide. The leading cause of death is respiratory infections. Children with BOS can have feeding difficulties, recurring respiratory infections, sleep apnea, developmental delay, failure to thrive, abnormal hair density and length, Wilm’s Tumors, brain abnormalities, silent aspiration, and other issues.

Perlman syndrome is an uncommon genetic disorder grouped with overgrowth syndrome in which an abnormal increase is often noted at birth in the size of the body or a body part of the infant. The disorder, also called renal hamartomas, nephroblastomatosis and fetal gigantism, has also been grouped with Renal cell carcinoma. The characteristic features include polyhydramnios, fetal overgrowth, including macrocephaly, neonatal macrosomia, visceromegaly, dysmorphic facial features, and an increased risk for Wilms' tumor at an early age.

8p23.1 duplication syndrome is a rare genetic disorder caused by a duplication of a region from human chromosome 8. This duplication syndrome has an estimated prevalence of 1 in 64,000 births and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable phenotype including one or more of speech delay, developmental delay, mild dysmorphism, with prominent forehead and arched eyebrows, and congenital heart disease (CHD).

The majority of 22q11 duplications are inherited often from a parent with a normal or near-normal phenotype. This is in sharp distinction to 22q11 deletion syndrome where about 90% of cases are caused by mutations that occur "de novo".

Clinodactyly is an autosomal dominant trait that has variable expressiveness and incomplete penetrance.

Clinodactyly can be passed through inheritance and presents as either an isolated anomaly or a component manifestation of a genetic syndrome. Many syndromes are associated with clinodactyly, including Down Syndrome, Turner syndrome, Aarskog syndrome, Carpenter syndrome, Seckel syndrome, Cornelia de Lange syndrome, orofaciodigital syndrome 1, 13q deletion syndrome, XXYY syndrome and Silver–Russell syndrome.

When identified prenatally, for example during obstetric ultrasonography, it may be an indication for intrauterine sampling for fetal chromosome analysis as it is statistically correlated with increased risk of chromosome aberration in the fetus.