In itself, NSML is not a life-threatening diagnosis, most people diagnosed with the condition live normal lives. Obstructive cardiomyopathy and other pathologic findings involving the cardiovascular system may be a cause of death in those whose cardiac deformities are profound.

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.

Spanish researchers reported the development of a Costello mouse, with the G12V mutation, in early 2008. Although the G12V mutation is rare among children with Costello syndrome, and the G12V mouse does not appear to develop tumors as expected, information about the mouse model's heart may be transferrable to humans.

Italian and Japanese researchers published their development of a Costello zebrafish in late 2008, also with the G12V mutation. The advent of animal models may accelerate identification of treatment options.

In the two predominant mutations of NSML (Y279C and T468M) the mutations cause a loss of catalytic activity of the SHP2 protein (the gene product of the "PTPN11" gene), which is a previously unrecognized behavior for this class of mutations. This interferes with growth factor and related signalling. While further research confirms this mechanism, additional research is needed to determine how this relates to all of the observed effects of NSML.

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.

Recurrence in siblings and apparent transmission from parent to child has long suggested a genetic defect with autosomal dominant inheritance and variable expression. Mutations in the Ras/mitogen activated protein kinase signaling pathways are known to be responsible for ~70% of NS cases.

A person with NS has up to a 50% chance of transmitting it to their offspring. The fact that an affected parent is not always identified for children with NS suggests several possibilities:

1. Manifestations could be so subtle as to go unrecognized (variable expressivity)

2. NS is heterogeneous, comprising more than one similar condition of differing causes, and some of these may not be inherited.

3. A high proportion of cases may represent new, sporadic mutations.

Heterozygous mutations in "NRAS", "HRAS", "BRAF", "SHOC2", "MAP2K1", "MAP2K2", and "CBL" have also been associated with a smaller percentage of NS and related phenotypes.

A condition known as "neurofibromatosis-Noonan syndrome" is associated with neurofibromin.

Costello syndrome, also called faciocutaneoskeletal syndrome or FCS syndrome, is a rare genetic disorder that affects many parts of the body. It is characterized by delayed development and delayed mental progression, distinctive facial features, unusually flexible joints, and loose folds of extra skin, especially on the hands and feet. Heart abnormalities are common, including a very fast heartbeat (tachycardia), structural heart defects, and overgrowth of the heart muscle (hypertrophic cardiomyopathy). Infants with Costello syndrome may be large at birth, but grow more slowly than other children and have difficulty feeding. Later in life, people with this condition have relatively short stature and many have reduced levels of growth hormones. It is a RASopathy.

Beginning in early childhood, people with Costello syndrome have an increased risk of developing certain cancerous and noncancerous tumors. Small growths called papillomas are the most common noncancerous tumors seen with this condition. They usually develop around the nose and mouth or near the anus. The most frequent cancerous tumor associated with Costello syndrome is a soft tissue tumor called a rhabdomyosarcoma. Other cancers also have been reported in children and adolescents with this disorder, including a tumor that arises in developing nerve cells (neuroblastoma) and a form of bladder cancer (transitional cell carcinoma).

Costello Syndrome was discovered by Dr Jack Costello, a New Zealand Paediatrician in 1977. He is credited with first reporting the syndrome in the Australian Paediatric Journal, Volume 13, No.2 in 1977.

Low-set ears are ears with depressed positioning of the pinna two or more standard deviations below the population average.

It can be associated with conditions such as:

- Down's syndrome

- Turner Syndrome

- Noonan syndrome

- Patau syndrome

- DiGeorge syndrome

- Cri du chat syndrome

- Edwards syndrome

- Fragile X syndrome

It is usually bilateral, but can be unilateral in Goldenhar syndrome.

Triple-A syndrome is associated with mutations in the "AAAS" gene, which encodes a protein known as ALADIN (ALacrima Achalasia aDrenal Insufficiency Neurologic disorder). In 2000, Huebner "et al." mapped the syndrome to a 6 cM interval on human chromosome 12q13 near the type II keratin gene cluster. Since inheritance and gene for the association is known, early diagnosis can allow genetic counseling.

The RASopathies are developmental syndromes caused by germline mutations (or in rare cases by somatic mosaicism) in genes that alter the Ras subfamily and mitogen-activated protein kinases that control signal transduction, including:

- Capillary malformation-AV malformation syndrome

- Autoimmune lymphoproliferative syndrome

- Cardiofaciocutaneous syndrome

- Hereditary gingival fibromatosis type 1

- Neurofibromatosis type 1

- Noonan syndrome

- Costello syndrome, Noonan-like

- Legius syndrome, Noonan-like

- Noonan syndrome with multiple lentigines, formerly called LEOPARD syndrome, Noonan-like

Males are twice as likely as females to have this characteristic, and it tends to run in families. In its non-symptomatic form, it is more common among Asians and Native Americans than among other populations, and in some families there is a tendency to inherit the condition unilaterally, that is, on one hand only.

The presence of a single transverse palmar crease can be, but is not always, a symptom associated with abnormal medical conditions, such as fetal alcohol syndrome, or with genetic chromosomal abnormalities, including Down Syndrome (chromosome 21), cri du chat syndrome (chromosome 5), Klinefelter syndrome, Wolf-Hirschhorn Syndrome, Noonan syndrome (chromosome 12), Patau syndrome (chromosome 13), IDIC 15/Dup15q (chromosome 15), Edward's syndrome (chromosome 18), and Aarskog-Scott syndrome (X-linked recessive), or autosomal recessive disorder, such as Leaukocyte adhesion deficiency-2 (LAD2). A unilateral single palmar crease was also reported in a case of chromosome 9 mutation causing Nevoid basal cell carcinoma syndrome and Robinow syndrome. It is also sometimes found on the hand of the affected side of patients with Poland Syndrome, and craniosynostosis.

Revesz syndrome has so far been observed only in children. There is not much information about the disease because of its low frequency in general population and under reporting of cases.

Costello and Noonan syndrome are similar to CFC and their phenotypic overlap may be due to the biochemical relationship of the genes mutated in each syndrome to each other. Genes that are mutated in all three of these syndromes encode proteins that function in the MAP kinase pathway.

- Mutations that cause CFC are found in the KRAS, BRAF, MEK1 and MEK2 genes.

- Costello syndrome is caused by mutations in HRAS.

- Mutations that cause Noonan syndrome have been found in PTPN11 and SOS1.

The relative severity of CFC when compared to Noonan syndrome may reflect the position in the biochemical pathway each gene occupies.

- Shp2, the protein product of the PTPN11, appears to regulate the MAP kinase pathway at or above the level of SOS1.

- SOS1 in turn regulates the activities of RAS, RAF, MEK, ERK and p90RSK.

- SOS1 has been demonstrated to be a target of negative feedback by ERK and p90RSK.

Thus, any activating mutation downstream of SOS1 may be subject to less regulation that may mitigate the consequence of such mutations giving rise to the phenotypic differences seen between these syndromes.

3q29 microdeletion syndrome is a rare genetic disorder resulting from the deletion of a segment of chromosome 3. This syndrome was first described in 2005.

Triple-A syndrome or AAA syndrome, also known as achalasia-addisonianism-alacrima syndrome or Allgrove syndrome, is a rare autosomal recessive congenital disorder. In most cases, there is no family history of it. The syndrome was first identified by Jeremy Allgrove and colleagues in 1978. The syndrome involves achalasia, addisonianism (adrenal insufficiency of primary type), and alacrima (insufficiency of tears). Alacrima is usually the earliest manifestation. It is a progressive disorder that can take years to develop the full blown clinical picture.

While not always pathological, it can present as a birth defect in multiple syndromes including:

- Catel–Manzke syndrome

- Bloom syndrome

- Coffin–Lowry syndrome

- congenital rubella

- Cri du chat syndrome

- DiGeorge's syndrome

- Ehlers-Danlos syndrome

- fetal alcohol syndrome

- Hallermann-Streiff syndrome

- Hemifacial microsomia (as part of Goldenhar syndrome)

- Juvenile idiopathic arthritis

- Marfan syndrome

- Noonan syndrome

- Pierre Robin syndrome

- Prader–Willi syndrome

- Progeria

- Russell-Silver syndrome

- Seckel syndrome

- Smith-Lemli-Opitz syndrome

- Treacher Collins syndrome

- Trisomy 13 (Patau syndrome)

- Trisomy 18 (Edwards syndrome)

- Wolf–Hirschhorn syndrome

- X0 syndrome (Turner syndrome)

Individuals with the disorder usually have distinctive malformations of the craniofacial area including an unusually large head (macrocephaly), prominent forehead, and abnormal narrowing of both sides of the forehead (bitemporal constriction); The nose can be upturned and short with a low nasal bridge; and large ears that are abnormally rotated toward the back of the head. In many cases, affected individuals also have downward slanting eyelid folds, widely spaced eyes, drooping of the upper eyelids, inward deviation of the eyes, and other eye abnormalities including absent eyebrows and eyelashes.

NBCCS has an incidence of 1 in 50,000 to 150,000 with higher incidence in Australia. One aspect of NBCCS is that basal-cell carcinomas will occur on areas of the body which are not generally exposed to sunlight, such as the palms and soles of the feet and lesions may develop at the base of palmar and plantar pits.

One of the prime features of NBCCS is development of multiple BCCs at an early age, often in the teen years. Each person who has this syndrome is affected to a different degree, some having many more characteristics of the condition than others.

Revesz syndrome is a genetic disease thought to be caused by short telomeres. Patients with Revesz syndrome have presented with heterozygous mutations in TINF2 gene which is located on chromosome 14q12. There is no treatment for this disease yet.

Muenke syndrome is caused by a specific gene mutation in the FGFR3 gene. The mutation arises randomly; there is no full understanding for what causes this mutation. This mutation causes the FGFR3 protein to be overly active; it interferes with normal bone growth, and allows skull bones to fuse prematurely. There is no connection between anything mother did (or did not do) to activate the syndrome. If neither of the parents have Muenke syndrome, chances of having another child with the syndrome are minimal.

This condition is inherited in an autosomal dominant pattern. This means if a parent has Muenke syndrome, every newborn has a 50% chance of inheriting the syndrome.

It can be detected by the naked eye as well as dental or skull X-Ray testing.

Muenke syndrome is inherited in an autosomal dominant pattern. In some cases, an affected person inherits the mutation from one affected parent. If a patient is shown to have Muenke, they have a 50/50 chance of passing it on to their children. Not all cases of Muenke however is obvious. Other cases may result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.

A single mutation in the FGFR3 gene cause this syndrome. The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. This mutation causes the FGFR3 protein to be overly active, which interferes with normal bone growth and allows the bones of the skull to fuse before they should.

As stated by researchers at the University of Washington, Muenke syndrome is inherited in an autosomal dominant manner with incomplete penetrance and variable expressivity.” Prenatal diagnosis for pregnancies at increased risk is possible if the defining mutation has been identified in the family (Agochukwu et.al. 2006). According to the article "Craniosynostosis: Molecular Genetics," penetrance is higher in females (87%) than in males (76%). Muenke syndrome is estimated to account for 25%-30% of all genetic causes of craniosynostosis according to the Journal of Anatomy.

Aphalangy, hemivertebrae and urogenital-intestinal dysgenesis is an extremely rare syndrome, described only in three siblings. It associates hypoplasia or aplasia of phalanges of hands and feet, hemivertebrae and various urogenital and/or intestinal abnormalities. Intrafamilial variability is important as one sister had lethal abnormalities (Potter sequence and pulmonary hypoplasia), while her affected brother was in good health with normal psychomotor development at 6 months of age. Prognosis seems to depend mainly on the severity of visceral malformations. Etiology and inheritance remain unknown.

NF-1 is a progressive and diverse condition, making the prognosis difficult to predict. The NF-1 gene mutations manifest the disorder differently even amongst people of the same family. This phenomenon is called variable expressivity. For example, some individuals have no symptoms, while others may have a manifestation that is rapidly more progressive and severe.

For many NF-1 patients, a primary concern is the disfigurement caused by cutaneous/dermal neurofibromas, pigmented lesions, and the occasional limb abnormalities. However, there are many more severe complications caused by NF-1, although most of them are quite rare. Many NF patients live perfectly normal and uninterrupted lives.

Short rib – polydactyly syndrome is a family of four closely related dysplasias:

- I - "Saldino-Noonan type"

- II - "Majewski type"

- III - "Verma-Naumoff type" (associated with DYNC2H1)

- IV - "Beemer-Langer type"