Since tetrasomy 9p is not usually inherited, the risk of a couple having a second child with the disorder is minimal. While patients often do not survive to reproductive age, those who do may or may not be fertile. The risk of a patient's child inheriting the disorder is largely dependent on the details of the individual's case.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

About half of all 'marker' chromosomes are idic(15) but idic(15) in itself is one of the rare chromosome abnormalities. Incidence at birth appears to be 1 in 30,000 with a sex ratio of almost 1:1; however, since dysmorphic features are absent or subtle and major malformations are rare, chromosome analysis may not be thought to be indicated, and some individuals, particularly in the older age groups, probably remain undiagnosed. There are organizations for families with idic(15) children that offer extensive information and support.

A review from 2000 stated that life expectancy was reduced because of a tendency to develop cancer relatively early as well as deaths due to infections related to immunodeficiency.

Though the outcome for individuals with either form of the tetrasomy is highly variable, mosaic individuals consistently experience a more favourable outcome than those with the non-mosaic form. Some affected infants die shortly after birth, particularly those with the non-mosaic tetrasomy. Many patients do not survive to reproductive age, while others are able to function relatively normally in a school or workplace setting. Early diagnosis and intervention has been shown to have a strong positive influence on the prognosis.

The life expectancy of people with A-T is highly variable. The average is approximately 25 years, but continues to improve with advances in care. The two most common causes of death are chronic lung disease (about one-third of cases) and cancer (about one-third of cases).

At this time, there are no other phenotypes (observable expressions of a gene) that have been discovered for mutations in the ESCO2 gene.

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 outlook for individuals with EDS depends on the type of EDS they have. Symptoms vary in severity, even within one sub-type, and the frequency of complications changes individually. Some people have negligible symptoms while others are severely restricted in their daily life. Extreme joint instability, chronic musculoskeletal pain, degenerative joint disease, frequent injuries, and spinal deformities may limit mobility. Severe spinal deformities may affect breathing. In the case of extreme joint instability, dislocations may result from simple tasks such as rolling over in bed or turning a doorknob. Secondary conditions such as autonomic dysfunction or cardiovascular problems, occurring in any type, can affect prognosis and quality of life. Severe mobility-related disability is seen more often in Hypermobility-type than in Classical-type or Vascular-type.

Although all types are potentially life-threatening, the majority of individuals will have a normal lifespan. However, those with blood vessel fragility have a high risk of fatal complications. Arterial rupture is the most common cause of sudden death in EDS. Spontaneous arterial rupture most often occurs in the second or third decade, but can occur at any time. The median life-expectancy in the population with Vascular EDS is 48 years.

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.

At the present time, there is no specific treatment that can undo any chromosomal abnormality, nor the genetic pattern seen in people with idic(15). The extra chromosomal material in those affected was present at or shortly after conception, and its effects on brain development began taking place long before the child was born. Therapies are available to help address many of the symptoms associated with idic(15). Physical, occupational, and speech therapies along with special education techniques can stimulate children with idic(15) to develop to their full potential.

In terms of medical management of the symptoms associated with Chromosome 15q11.2-q13.1 Duplication Syndrome, families should be aware that individuals with chromosome 15 duplications may tolerate medications differently and may be more sensitive to side effects for some classes of medications, such as the serotonin reuptake inhibitor type medications (SSRI).

Thus, these should be used with caution and any new medication should be instituted in a controlled setting, with slow titration of levels and with a clear endpoint as to what the expected outcome for treatment is.

There is an increased risk of sudden, unexpected death among children and adults with this syndrome. The full cause is not yet understood but it is generally attributed to SUDEP (Sudden Unexplained Death in Epilepsy).

Fragile sites are associated with numerous disorders and diseases, both heritable and not. The FRAXA site is perhaps most famous for its role in Fragile X syndrome, but fragile sites are clinically implicated in many other important diseases, such as cancer.

Individuals of all races and ethnicities are affected equally. The incidence worldwide is estimated to be between 1 in 40,000 and 1 in 100,000 people.

Chromosome instability syndromes are a group of inherited conditions associated with chromosomal instability and breakage. They often lead to an increased tendency to develop certain types of malignancies.

The following chromosome instability syndromes are known:

- Ataxia telangiectasia

- Ataxia telangiectasia-like disorder

- Bloom syndrome

- Fanconi anaemia

- Nijmegen breakage syndrome

This condition is rare. Only four cases have been described up to 2017.

RIDDLE syndrome is a rare genetic syndrome. The name is an acronym for Radiosensitivity, ImmunoDeficiency Dysmorphic features and LEarning difficulties.

Bloom syndrome is an extremely rare disorder in most populations and the frequency of the disease has not been measured in most populations. However, the disorder is relatively more common amongst people of Central and Eastern European (Ashkenazi) Jewish background. Approximately 1 in 48,000 Ashkenazi Jews are affected by Bloom syndrome, who account for about one-third of affected individuals worldwide.

Trisomy 8 mosaicism affects wide areas of chromosome 8 containing many genes, and can thus be associated with a range of symptoms.

- Mosaic trisomy 8 has been reported in rare cases of Rothmund-Thomson syndrome, a genetic disorder associated with the DNA helicase RECQL4 on chromosome 8q24.3. The syndrome is "characterized by skin atrophy, telangiectasia, hyper- and hypopigmentation, congenital skeletal abnormalities, short stature, premature aging, and increased risk of malignant disease".

- Some individuals trisomic for chromosome 8 were deficient in production of coagulation factor VII due to a factor 7 regulation gene (F7R) mapped to 8p23.3-p23.1.

- Trisomy and other rearrangements of chromosome 8 have also been found in tricho–rhino–phalangeal syndrome.

- Small regions of chromosome 8 trisomy and monosomy are also created by recombinant chromosome 8 syndrome (San Luis Valley syndrome), causing anomalies associated with tetralogy of Fallot, which results from recombination between a typical chromosome 8 and one carrying a parental paracentric inversion.

- Trisomy is also found in some cases of chronic myeloid leukaemia, potentially as a result of karyotypic instability caused by the fusion gene.

Campomelic dysplasia has a reported incidence of 0.05-0.09 per 10000 live births.

In nearly 95% of the cases, death occurs in the neonatal period due to respiratory distress, generally related to small chest size or insufficient development of the trachea and other upper airway structures.

Among survivors of CMD, the skeletal malformations change over time to include worsening scoliosis or kyphosis resulting in decreased trunk size relative to the limb length. Neurological damage is also often seen including mental retardation and deafness. Even among survivors of the prenatal period, CMD patients have shortened life spans due to lifelong respiratory issues. Those patients with ambiguous genitalia or sex reversal at birth, of course, maintain that state, and are either sterile or have reduced fertility.

Nijmegen breakage syndrome (NBS), also known as Berlin breakage syndrome, ataxia telangiectasia variant 1 (AT-V1) and Seemanova syndrome, is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the double Holliday junction DNA repair mechanism and/or the synthesis dependent strand annealing mechanism for repairing double strand breaks in DNA (see Homologous recombination).

NBS1 codes for a protein (nibrin) that has two major functions: (1) to stop the cell cycle in the S phase, when there are errors in the cell DNA (2) to interact with FANCD2 that can activate the BRCA1/BRCA2 pathway of DNA repair. This explains why mutations in the NBS1 gene lead to higher levels of cancer (see Fanconi anemia, Cockayne syndrome.)

The name derives from the Dutch city Nijmegen where the condition was first described.

Most people with NBS have West Slavic origins. The largest number of them live in Poland.

Ehlers–Danlos syndrome is an inherited disorder estimated to occur in about 1 in 5,000 births worldwide. Initially, prevalence estimates ranged from 1 in 250,000 to 1 in 500,000 people, but these estimates were soon found to be vastly inaccurate as the disorder received further study and medical professionals became more adept at accurately diagnosing EDS. In fact, many experts now believe that Ehlers–Danlos syndrome may be far more common than the currently accepted estimate due to the wide range of severities with which the disorder presents.

The prevalence of the 13 types differs dramatically. The most commonly occurring is the Hypermobility type, followed by the Classical type. The other types of Ehlers–Danlos syndrome are very rare. For example, fewer than ten infants and children with the dermatosparaxis type have been described worldwide. Some types of Ehlers–Danlos are more common in Ashkenazi Jews. For example, the chance of being a carrier for type-VIIc Ehlers–Danlos is 1 in 248 in Ashkenazi Jews, whereas the prevalence of this mutation in the general population is 1 in 2,000.

Bloom syndrome (often abbreviated as BS in literature), also known as Bloom-Torre-Machacek syndrome, is a rare autosomal recessive disorder characterized by short stature, predisposition to the development of cancer and genomic instability. BS is caused by mutations in the BLM gene leading to mutated DNA helicase protein formation. Cells from a person with Bloom syndrome exhibit a striking genomic instability that includes excessive crossovers between homologous chromosomes and sister chromatid exchanges (SCEs). The condition was discovered and first described by New York dermatologist Dr. David Bloom in 1954.

Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques. Smaller deletions result in Microdeletion syndrome, which are detected using fluorescence in situ hybridization (FISH)

Examples of chromosomal deletion syndromes include 5p-Deletion (cri du chat syndrome), 4p-Deletion (Wolf-Hirschhorn syndrome), Prader–Willi syndrome, and Angelman syndrome.

A chromosomal fragile site is a specific heritable point on a chromosome that tends to form a gap or constriction and may tend to break when the cell is exposed to partial replication stress. Based on their frequency, fragile sites are classified as "common" or "rare". To date, more than 120 fragile sites have been identified in the human genome.

Common fragile sites are considered part of normal chromosome structure and are present in all (or nearly all) individuals in a population. Under normal conditions, most common fragile sites are not prone to spontaneous breaks. Common fragile sites are of interest in cancer studies because they are frequently affected in cancer and they can be found in healthy individuals. Sites FRA3B (harboring the "FHIT" gene) and FRA16D (harboring the "WWOX" gene) are two well known examples and have been a major focus of research.

Rare fragile sites are found in less than 5% of the population, and are often composed of two- or three-nucleotide repeats. They are often susceptible to spontaneous breakage during replication, frequently affecting neighboring genes. Clinically, the most important rare fragile site is FRAXA, which is associated with the fragile X syndrome, the most common cause of hereditary mental retardation.

In most cases, between the age of 2 and 4 oculomotor signals are present. Between the age of 2 and 8, telangiectasias appears. Usually by the age of 10 the child needs a wheel chair. Individuals with autosomal recessive cerebellum ataxia usually survive till their 20s; in some cases individuals have survived till their 40s or 50s.