PWS affects approximately 1 in 10,000 to 1 in 25,000 newborns. There are more than 400,000 people who live with PWS around the world.

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.

Lujan–Fryns syndrome is a rare X-linked dominant syndrome, and is therefore more common in males than females. Its prevalence within the general population has not yet been determined.

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.

As its name indicates, a person with the syndrome has one Y chromosome and four X chromosomes on the 23rd pair, thus having 49 chromosomes rather than the normal 46. As with most categories of aneuploidy disorders, 49,XXXXY syndrome is often accompanied by intellectual disability. It can be considered a form of 47, XXY Klinefelter syndrome, or a variant of it.

It is genetic but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The probability of inheriting the disease is about 1%.

The individuals with this syndrome are males, but 49, XXXXX also exists with similar characteristics.

Opitz G/BBB Syndrome is a rare genetic condition caused by one of two major types of mutations: MID1 mutation on the short (p) arm of the X chromosome or a mutation of the 22q11.2 gene on the 22nd chromosome. Since it is a genetic disease, it is an inherited condition. However, there is an extremely wide variability in how the disease presents itself.

In terms of prevention, several researchers strongly suggest prenatal testing for at-risk pregnancies if a MID1 mutation has been identified in a family member. Doctors can perform a fetal sex test through chromosome analysis and then screen the DNA for any mutations causing the disease. Knowing that a child may be born with Opitz G/BBB syndrome could help physicians prepare for the child’s needs and the family prepare emotionally. Furthermore, genetic counseling for young adults that are affected, are carriers or are at risk of carrying is strongly suggested, as well (Meroni, Opitz G/BBB syndrome, 2012). Current research suggests that the cause is genetic and no known environmental risk factors have been documented. The only education for prevention suggested is genetic testing for at-risk young adults when a mutation is found or suspected in a family member.

Since the symptoms caused by this disease are present at birth, there is no “cure.” The best cure that scientists are researching is awareness and genetic testing to determine risk factors and increase knowledgeable family planning. Prevention is the only option at this point in time for a cure.

Turner syndrome occurs in between one in 2000 and one in 5000 females at birth.

Approximately 99 percent of fetuses with Turner syndrome spontaneously terminate during the first trimester. Turner syndrome accounts for about 10 percent of the total number of spontaneous abortions in the United States.

GMS syndrome is a syndrome characterised by goniodysgenesis, intellectual disability, and short stature.

Some people may have some mental slowness, but children with this condition often have good social skills. Some males may have problems with fertility.

Affected individuals have a somewhat shortened lifespan. The maximum described lifespan is 67 years. Adults with 13q deletion syndrome often need support services to maintain their activities of daily living, including adult day care services or housing services.

PWS is commonly associated with development of strabismus. In one study, over 50% of patients had strabismus, mainly esotropia.

This disorder is present at birth, however, it may not be understood until several years after birth. Acrodysostosis affects males and females in almost similar numbers. It is difficult to determine the frequency of acrodysostosis in the population as many cases of this disorder cannot be diagnosed properly.

Urban–Rogers–Meyer syndrome, also known as Prader–Willi habitus, osteopenia, and camptodactyly or Urban syndrome, is an extremely rare inherited congenital disorder first described by Urban et al. (1979). It is characterized by genital anomalies, mental retardation, obesity, contractures of fingers, and osteoporosis, though further complications are known.

The aneuploidy is thought to be caused by problems occurring during meiosis, either in the mother or in both the mother and father. Successive nondisjunctions have been observed in the mother of at least one patient.

The features of the syndrome likely arise due to failure of X-inactivation and the presence of multiple X chromosomes from the same parent causing problems with parental imprinting. In theory, X-inactivation should occur and leave only one X chromosome active in each cell. However, failure of this process has been observed in one individual studied. The reason for this is thought to be the presence of an unusually large, and imbalanced, number of X chromosomes interfering with the process.

There have been 30 cases of Marden-Walker Syndrome reported since 1966. The first case of this was in 1966 a female infant was diagnosed with blepharophimosis, joint contractures, arachnodactyly and growth development delay. She ended up passing at 3 months due to pneumonia.

Treatment can involve operations to lengthen the leg bones, which involves many visits to the hospital. Other symptoms can be treated with medicine or surgery. Most female patients with the syndrome can live a long and normal life, while males have only survived in rare cases.

Ring chromosome 14 syndrome is extremely rare, the true rate of occurrence is unknown (as it is "less than" 1 per 1,000,000), but there are at least 50 documented cases in the literature.

The exact role that these risk factors play in the process leading to rupture is unclear. Aortic root dilatation is thought to be due to a mesenchymal defect as pathological evidence of cystic medial necrosis has been found by several studies. The association between a similar defect and aortic dilatation is well established in such conditions such as Marfan syndrome. Also, abnormalities in other mesenchymal tissues (bone matrix and lymphatic vessels) suggests a similar primary mesenchymal defect in patients with Turner syndrome. However, no evidence suggests that patients with Turner syndrome have a significantly higher risk of aortic dilatation and dissection in absence of predisposing factors. So, the risk of aortic dissection in Turner syndrome appears to be a consequence of structural cardiovascular malformations and hemodynamic risk factors rather than a reflection of an inherent abnormality in connective tissue. The natural history of aortic root dilatation is unknown, but because of its lethal potential, this aortic abnormality needs to be carefully followed.

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 2007 study followed 112 individuals for a mean of 12 years (mean age 25.3, range 12–71). No patient died during follow-up, but several required medical interventions. The mean final heights were 167 and 153 cm for men and women, respectively, which is approximately 2 standard deviations below normal.

Emanuel Syndrome can be diagnosed with a karyotype, with FISH, or with a chromosomal microarray analysis. .

Genitopatellar Syndrome is an autosomal dominant inheritance where the mutation in the KAT6B causes the syndrome. The KAT6B gene is responsible for making an enzyme called histone acetyltransferase which functions in regulating and making of histone which are proteins that attach to DNA and give the chromosomes their shape. The function of histone acetyltransferase produced from KAT6B is unknown but it is considered as a regulator of early developments. There is little known about how the mutation in the KAT6B causes the syndrome but researchers suspects that the mutations occur near the end of the KAT6B gene and causes it to produce shortened acetyltransferase enzyme. The shortened enzyme alters the regulation of other genes. On the other hand, the mutation of KAT6B leading to the specific features of genitopatellar syndrome is still not surely proven.

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.

Hennekam syndrome also known as intestinal lymphagiectasia–lymphedema–mental retardation syndrome, is an autosomal recessive disorder consisting of intestinal lymphangiectasia, facial anomalies, peripheral lymphedema, and mild to moderate levels of growth and intellectual disability.

It is also known as "lymphedema-lymphangiectasia-mental retardation syndrome".

In a subset of patients it is associated with CCBE1 according research published by its namesake, Raoul Hennekam. Other causal mutations were found in the FAT4 gene. Previously, mutations in the FAT4 gene had been only associated with van Maldergem syndrome. The molecular mechanism of the lymphedema phenotype in CCBE1-associated cases was identified as a diminished ability of the mutated CCBE1 to accelerate and focus the activation of the primary lymphangiogenic growth factor VEGF-C.