As the syndrome is due to a chromosomal non-disjunction event, the recurrence risk is not high compared to the general population. There has been no evidence found that indicates non-disjunction occurs more often in a particular family.

Exposure of spermatozoa to lifestyle, environmental and/or occupational hazards may increase the risk of aneuploidy. Cigarette smoke is a known aneugen (aneuploidy inducing agent). It is associated with increases in aneuploidy ranging from 1.5 to 3.0-fold. Other studies indicate factors such as alcohol consumption, occupational exposure to benzene, and exposure to the insecticides fenvalerate and carbaryl also increase aneuploidy.

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.

Patients have an essentially normal life expectancy but require regular medical follow-up.

The condition 48,XXYY is not inherited; it usually occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. In 48,XXYY syndrome, the extra sex chromosomes almost always come from a sperm cell. Nondisjunction may cause a sperm cell to gain two extra sex chromosomes, resulting in a sperm cell with three sex chromosomes (one X and two Y chromosomes). If that sperm cell fertilizes a normal egg cell with one X chromosome, the resulting child will have two X chromosomes and two Y chromosomes in each of the body's cells.

In a small percentage of cases, 48,XXYY syndrome results from nondisjunction of the sex chromosomes in a 46,XY embryo very soon after fertilization has occurred. This means that an normal sperm cell with one Y chromosome fertilized a normal egg cell with one X chromosome, but right after fertilization nondisjunction of the sex chromosomes caused the embryo to gain two extra sex chromosomes, resulting in a 48,XXYY embryo.

Human trisomies compatible with live birth, other than Down syndrome (trisomy 21), are Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13). Complete trisomies of other chromosomes are usually not viable and represent a relatively frequent cause of miscarriage. Only in rare cases of a mosaicism, the presence of a normal cell line, in addition to the trisomic cell line, may support the development of a viable trisomy of the other chromosomes.

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.

The cause of 48, XXXY can be from non-disjunction in the paternal sperm or non-disjunction in the maternal oocyte. The most likely scenario for the existence of this aneuploidy is that each parent (maternal and paternal) equally contributed to it, by the mother giving an XX and the father giving an XY.

In the case where the sperm is the genetic cause of 48, XXXY syndrome, the sperm would have to contain two X chromosomes and one Y chromosome. This would be caused by two non-disjunction events in spermatogenesis, both meosis I and meosis II. The duplicated X chromosome in the sperm would have to fail to separate in both meosis I and meosis II for a sperm as well as the X and Y chromosomes would have to be in the same sperm. Then the XXY sperm would fertilize a normal oocyte to make a XXXY zygote.

In the case where the oocyte is the genetic cause of 48, XXXY syndrome the oocyte would contain three X chromosome. This would be caused by two non-disjunction events during oogenesis. In meosis I both sets of duplicated X chromosomes would have to be not separated. Then in meosis II one set of X chromosomes would have to not separate and the other set would separate resulting in one oocyte with three X chromosomes. A normal sperm containing a Y chromosome would have to fertilize the XXX oocyte to make a XXXY zygote.

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.

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.

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.

Triple X syndrome is not inherited, but usually, occurs as an event during the formation of reproductive cells (ovum and sperm). An error in cell division called nondisjunction can result in reproductive cells with additional chromosomes. For example, an oocyte or sperm cell may gain an extra copy of the X chromosome as a result of the non-disjunction. If one of these cells contributes to the genetic makeup of a child, the child will have an extra X chromosome in each of her cells. In some cases, trisomy X occurs during cell division in early embryonic development.

Some females with triple X syndrome have an extra X chromosome in only some of their cells. These cases are called 46,XX/47,XXX mosaics.

Triple X syndrome occurs in around 1 in 1,000 girls. On average, five to ten girls with triple X syndrome are born in the United States each day.

Unlike Borjeson-Forssman-Lehmann syndrome, a disorder that was determined to be very similar to WTS, the individuals with Wilson–Turner syndrome do not develop cataracts or hypermetropia later in life. By far, the most debilitating part of this disorder is intellectual disability. Many of the other symptoms are more easily managed through hormone treatment, proper diet and exercise, and speech therapy.

An individual exhibiting intellectual disability and other symptoms similar to LFS was found to have a terminal deletion of the subtelomeric region in the short arm of chromosome 5. Deletion of this area of chromosome 5 is associated with intellectual disability, psychotic behavior, autism, macrocephaly and hypernasal-like speech, as well as the disorder Cri du chat syndrome. Fryns (2006) suggests a detailed examination of chromosome 5 with FISH should be performed as part of the differential diagnosis of LFS.

Mutations in the "UPF3B" gene, also found on the X chromosome, are another cause of X-linked intellectual disability. "UPF3B" is part of the nonsense-mediated mRNA decay (NMD) complex, which performs mRNA surveillance, detecting mRNA sequences that have been erroneously truncated (shortened) by the presence of nonsense mutations. Mutations in "UPF3B" alter and prevent normal function of the NMD pathway, resulting in translation and expression of truncated mRNA sequences into malfunctioning proteins that can be associated with developmental errors and intellectual disability. Individuals from two families diagnosed with LFS and one family with FGS were found to have mutations in "UPF3B", confirming that the clinical presentations of the different mutations can overlap.

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.

Screening methods are mostly done for females to determine if they are carriers. Males do not have to be tested because those with the disorder will show symptoms close to the time they are born because the disorder is inherited from the X chromosome. Female can be tested if they are carriers by performing a X chromosome inactivation analysis on DNA isolated from the peripheral lymphocytes. The CAG repeat in this section must be amplified and methylated DNA must be sorted from unmethylated DNA with PCR. Carrier females will show skewed X-inactivation pattern (skewing close to 100%) with the mutated allele inactivated. This indicates a selection against cells with an active X chromosome with the mutated HDAC8 gene.

Trisomy 22 is a chromosomal disorder in which there are three copies of chromosome 22 rather than two. It is a frequent cause of spontaneous abortion during the first trimester of pregnancy. Progression to the second trimester and live birth are rare. This disorder is found in individuals with an extra copy or a variation of chromosome 22 in some or all cells of their body. There are many kinds of disorders associated with Trisomy 22:

Emanuel Syndrome is named after the genetic contributions made by researcher Dr. Beverly Emanuel. This condition is assigned to individuals born with an unbalanced 11/22 translocation. That is, a fragment of chromosome 11 is moved, or translocated, to chromosome 22.

22q11 Deletion Syndrome is a rare condition which occurs in approximately 1 in 4000 births. This condition is identified when a band in the q11.2 section of the arm of chromosome 22 is missing or deleted. This condition has several different names: 22q11.2 Deletion Syndrome, Velocardiofacial syndrome, DiGeorge Syndrome, Conotruncal Anomaly Face syndrome, Opitz G/BBB Syndrome, and Cayler Cardiofacial Syndrome. The effects of this disorder are different in each individual but similarities exist such as heart defects, immune system problems, a distinctive facial appearance, learning challenges, cleft palate, hearing loss, kidney problems, hypocalcemia, and sometimes psychiatric issues.

22q11 microduplication syndrome is the opposite of the 22q11 deletion syndrome: in this condition, a band of q.11.2 section of chromosome 22 is duplicated. Individuals carrying this deficiency are relatively “normal” as in they don’t possess any major birth defects or major medical illnesses. This microduplication is more common than the deletion; this might be due to the milder phenotype of the individuals.

Phelan-McDermid Syndrome / 22q13 Deletion Syndrome is a condition caused by the deletion of the tip of the q arm on chromosome 22. Most individuals with this disorder experience cognitive delays; low muscle tone; and sleeping, eating, and behavioural issues.

Chromosome Ring 22 is a rare disorder caused by the break and re-join of both ends of chromosome 22, forming a ring. The effects on the individual with this disorder are dependent on the amount of genetic information lost during the break/re-join. Major characteristics for this disorder are intellectual disability, muscle weakness and lack of coordination.

Cat Eye Syndrome / Schmid Fraccaro Syndrome is a condition caused by a partial trisomy or tetrasomy in chromosome 22. A small extra chromosome is found, made up of the top half of chromosome 22 and a portion of the q arm at the q11.2 break. This chromosome can be found three or four times. This syndrome is referred as “Cat Eye” due to the eye appearance of reported affected individuals who have coloboma of the iris; however, this feature is only seen in about half of the cases.

Mosaic trisomy 22 is a disorder in which an extra chromosome 22 is found only in some cells of the body. The severity of each case is determined by the number of cells with this extra copy. Some characteristics of individuals with this condition are cardiac abnormalities, growth retardation, mental delay, etc.

Complete Trisomy 22 is in contrast with Mosaic trisomy 22; this disorder is characterized by an extra copy of chromosome 22 which is found in each cell of the body of the affected individual. These cases are very rare, and most of the affected individuals die before birth or shortly after.

Since the syndrome is caused by a genetic mutation in the individual's DNA, a cure is not available. Treatment of the symptoms and management of the syndrome, however, is possible.

Depending on the manifestation, surgery, increased intake of glucose, special education, occupational therapy, speech therapy, and physical therapy are some methods of managing the syndrome and associated symptoms.

Males with pathogenic "MECP2" mutations usually die within the first 2 years from severe encephalopathy, unless they have an extra X chromosome (often described as Klinefelter syndrome), or have somatic mosaicism.

Male fetuses with the disorder rarely survive to term. Because the disease-causing gene is located on the X chromosome, a female born with an MECP2 mutation on her X chromosome has another X chromosome with an ostensibly normal copy of the same gene, while a male with the mutation on his X chromosome has no other X chromosome, only a Y chromosome; thus, he has no normal gene. Without a normal gene to provide normal proteins in addition to the abnormal proteins caused by a MECP2 mutation, the XY karyotype male fetus is unable to slow the development of the disease, hence the failure of many male fetuses with a MECP2 mutation to survive to term.

Females with a MECP2 mutation, however, have a non-mutant chromosome that provides them enough normal protein to survive longer. Research shows that males with Rett syndrome may result from Klinefelter's syndrome, in which the male has an XXY karyotype. Thus, a non-mutant "MECP2" gene is necessary for a Rett's-affected embryo to survive in most cases, and the embryo, male or female, must have another X chromosome.

There have, however, been several cases of 46,XY karyotype males with a MECP2 mutation (associated with classical Rett syndrome in females) carried to term, who were affected by neonatal encephalopathy and died before 2 years of age. The incidence of Rett syndrome in males is unknown, partly owing to the low survival of male fetuses with the Rett syndrome-associated MECP2 mutations, and partly to differences between signs caused by MECP2 mutations and those caused by Rett's.

Females can live up to 40 years or more. Laboratory studies on Rett syndrome may show abnormalities such as:

- EEG abnormalities from 2 years of age

- atypical brain glycolipids

- elevated CSF levels of "beta"-endorphin and glutamate

- reduction of substance P

- decreased levels of CSF nerve growth factors

A high proportion of deaths are abrupt, but most have no identifiable cause; in some instances death is the result most likely of:

- spontaneous brainstem dysfunction

- cardiac arrest, likely due to long QT syndrome, ventricular tachycardia or other arrhythmias

- seizures

- gastric perforation

In a normal situation, all the cells in an individual will have 46 chromosomes with one being an X and one a Y or with two Xs. However, sometimes during this complicated early copying process (DNA replication and cell division), one chromosome can be lost. In 45,X/46,XY, most or all of the Y chromosome is lost in one of the newly created cells. All the cells then made from this cell will lack the Y chromosome. All the cells created from the cells that have not lost the Y chromosome will be XY. The 46,XY cells will continue to multiply at the same time as the 45,X cells multiply. The embryo, then the fetus and then the baby will have what is called a 45,X/46,XY constitution. This is called a

mosaic karyotype because, like tiles in mosaic floors or walls, there is more than one type of cell.

There are many chromosomal variations that cause the 45,X/46,XY karyotype, including malformation (isodicentricism) of the Y chromosomes, deletions of Y chromosome or translocations of Y chromosome segments. These rearrangements of the Y chromosome can lead to partial expression of the SRY gene which may lead to abnormal genitals and testosterone levels.

A 2013 review stated that life expectancy for FXS was 12 years lower than the general population and that the causes of death were similar to those found for the general population.

The term “pure gonadal dysgenesis” (PGD) has been used to distinguish a group of patients from gonadal dysgenesis related to Turner syndrome. In the latter a distinct chromosomal aberration is present, while in PGD the chromosomal constellation is either 46,XX or 46,XY. Thus XX gonadal dysgenesis is also referred to as "PGD, 46 XX", and XY gonadal dysgenesis as "PGD, 46,XY" or Swyer syndrome. Patients with PGD have a normal chromosomal constellation but may have localized genetic alterations.

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.

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).