Potocki–Lupski syndrome (PTLS), also known as dup(17)p11.2p11.2 syndrome, trisomy 17p11.2 or duplication 17p11.2 syndrome, is a contiguous gene syndrome involving the microduplication of band 11.2 on the short arm of human chromosome 17 (17p11.2). The duplication was first described as a case study in 1996. In 2000, the first study of the disease was released, and in 2007, enough patients had been gathered to complete a comprehensive study and give it a detailed clinical description. PTLS is named for two researchers involved in the latter phases, Drs. Lorraine Potocki and James R. Lupski of Baylor College of Medicine.

PTLS was the first predicted of a homologous recombination (microdeletion or microduplication) where both reciprocal recombinations result in a contiguous gene syndrome. Its reciprocal disease is Smith–Magenis syndrome (SMS), in which the chromosome portion duplicated in PTLS is deleted altogether.

Potocki–Lupski syndrome is considered a rare disease, predicted to appear in at least 1 in 20,000 humans.

Symptoms of the syndrome include intellectual disability, autism, and other disorders unrelated to the listed symptoms.

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.

17q21.31 microdeletion syndrome (Koolen De Vries syndrome) is a rare genetic disorder caused by a deletion of a segment of chromosome 17 which contains six genes. This deletion syndrome was discovered independently in 2006 by three different research groups.

Marshall–Smith syndrome is not to be confused with:

- Marshall syndrome (aka.Periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA syndrome, see also: Periodic fever syndrome)

- Sotos (like) syndrome

- Weaver-Smith syndrome (WSS)

Respiratory complications are often cause of death in early infancy.

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.

The deletion that causes this disease can remove up to six different genes. These include:

- The uncharacterised protein C17orf69 (also known as FLJ25168).

- Corticotropin releasing hormone receptor 1 (CRHR1, also known as CRF-R, CRF1)

- Microtubule-associated protein tau (MAPT)

- The uncharacterised protein KIAA1267 (also known as DKFZP727C091)

Fraser syndrome (also known as Meyer-Schwickerath's syndrome, Fraser-François syndrome, or Ullrich-Feichtiger syndrome) is an autosomal recessive congenital disorder. Fraser syndrome is named for the geneticist George R. Fraser, who first described the syndrome in 1962.

Mowat–Wilson syndrome is a rare genetic disorder that was clinically delineated by Dr. D. R. Mowat and Dr. M. J. Wilson in 1998.

Ring chromosome 20, ring-shaped chromosome 20 or r(20) syndrome is a rare human chromosome abnormality where the two arms of chromosome 20 fuse to form a ring chromosome. The syndrome is associated with epileptic seizures, behaviour disorders and mental retardation.

When not all cells contain a ring chromosome 20, the individual suffers from ring 20 chromosomal mosaicism.Ring Chromosome 20 syndrome is thought to be an underdiagnosed condition. Since chromosomal analysis or karyotype testing is not a routine investigation for patients with epilepsy, the diagnosis of ring chromosome 20 syndrome is typically delayed or unrecognized.

The disorder is expressed in an autosomal dominant fashion and may result from a loss of function mutation or total deletion of the ZEB2 gene located on chromosome 2q22.

Two international research studies are currently underway. The International Genetic Study done with the Spinner Laboratory at The Children's Hospital of Philadelphia studies the ring 20 chromosome at the molecular level. The Clinical Research Study collects clinical information from parents to create a database of about the full spectrum of patients with ring chromosome 20 syndrome.

Children with CHARGE syndrome will vary greatly in their abilities in the classroom: some may need little support, while some may require full-time support and individualized programs.

Taking each of the various affected body systems into account is vital to the success of the child in the educational setting.

An important step in dealing with abnormal behavior is understanding why it is occurring and helping the child learn more appropriate methods of communicating. Before a child reaches age 18 (or the age of maturity in their country) doctors and specialists need to be found that will follow the individual in adulthood.

Human genetic disorders can be caused by ring chromosome formation. Although ring chromosomes are very rare, they have been found in all human chromosomes. Symptoms seen in patients carrying ring chromosomes are more likely to be caused by the deletion of genes in the telomeric regions of affected chromosomes, rather than by the formation of a ring structure itself. Almost all ring chromosome syndromes feature marked growth delay.

Ring chromosomes can be inherited or sporadic. Mosaicism is common and affects the severity of the condition. Location of fusion also affects severity due to loss of differing amounts of genetic material from the ends of chromosomes.

Disorders arising from the formation of a ring chromosome include:

Smith–Magenis syndrome is a chromosomal condition related to low copy repeats of specific segments of chromosome 17. Most people with SMS have a deletion of genetic material from a specific region of chromosome 17 (17p11.2). Although this region contains multiple genes, recently researchers discovered that the loss of one particular gene the retinoic acid induced 1 or "RAI1" is responsible for most of the characteristic features of this condition. Also, other genes within the chromosome 17 contribute to the variability and severity of the clinical features. The loss of other genes in the deleted region may help explain why the features of Smith–Magenis syndrome vary among affected individuals. A small percentage of people with Smith–Magenis syndrome have a mutation in the "RAI1" gene instead of a chromosomal deletion.

These deletions and mutations lead to the production of an abnormal or nonfunctional version of the "RAI1" protein. "RAI1" is a transcription factor that regulates the expression of multiple genes, including several that are involved in controlling circadian rhythm, such as "CLOCK". The groups led by James Lupski (Baylor College of Medicine) and Sarah Elsea (Virginia Commonwealth University) are in the process of studying the exact function of this gene in relation to Smith Magenis Syndrome.

SMS is typically not inherited. This condition usually results from a genetic change that occurs during the formation of reproductive cells (eggs or sperm) or in early fetal development. People with Smith–Magenis syndrome most often have no history of the condition in their family.

A ring chromosome is an aberrant chromosome whose ends have fused together to form a ring. Ring chromosomes were first discovered by Lilian Vaughan Morgan in 1926. A ring chromosome is denoted by the symbol "r" in human genetics and "R" in Drosophila genetics. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, but they may also arise spontaneously during development.

The duplication involved in PTLS is usually large enough to be detected through G-banding alone, though there is a high false negative rate. To ascertain the diagnosis when karyotyping results are unclear or negative, more sophisticated techniques such as subtelomeric fluorescent in-situ hybridization analysis and array comparative genomic hybridization (aCGH) may be used.

Smith–Magenis Syndrome (SMS) is a genetic disorder with features including intellectual disability, facial abnormalities, difficulty sleeping, and numerous behavioral problems such as self-harm. Smith–Magenis syndrome affects an estimated between 1 in 15,000 to 1 in 25,000 individuals.

It is a microdeletion syndrome characterized by an abnormality in the short (p) arm of chromosome 17 and is sometimes called the 17p- syndrome.

The treatment, and therefore prognosis, varies depending upon the underlying tumour.

Patients with abnormal cardiac and kidney function may be more at risk for hemolytic uremic syndrome

Mäkelä-Bengs et al. (1997,1998) performed a genome-wide screening and linkage analysis and assigned the LCCS locus to a defined region of 9q34.

Lethal congenital contracture syndrome 1 (LCCS1), also called Multiple contracture syndrome, Finnish type, is an autosomal recessive genetic disorder characterized by total immobility of a fetus, detectable at around the 13th week of pregnancy. LCCS1 invariably leads to prenatal death before the 32nd gestational week. LCCS1 is one of 40 Finnish heritage diseases. It was first described in 1985 and since then, approximately 70 cases have been diagnosed.

Foster–Kennedy syndrome (also known as Gowers–Paton–Kennedy syndrome, Kennedy's phenomenon or Kennedy's syndrome) refers to a constellation of findings associated with tumors of the frontal lobe.

Although "Foster–Kennedy syndrome" is equated with "Kennedy syndrome", it should not be confused with Kennedy disease, which is named for William R. Kennedy.

"Pseudo-Foster–Kennedy syndrome" is defined as one-sided optic atrophy with papilledema in the other eye but with the absence of a mass.

The incidence of VACTERL association is estimated to be approximately 1 in 10,000 to 1 in 40,000 live-born infants. It is seen more frequently in infants born to diabetic mothers. While most cases are sporadic, there are clearly families who present with multiple involved members.

A 2006 study followed 223 patients for a number of years. Of these, 15 died, with a median age of 65 years. The authors tentatively concluded that this is in line with a previously reported estimate of a shortened life expectancy of 10-15 years (12 in their data).