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

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.

In terms of diagnosing Bannayan–Riley–Ruvalcaba syndrome there is no current method outside the physical characteristics that may be present as signs/symptoms. There are, however, multiple molecular genetics tests (and cytogenetic test) to determine Bannayan–Riley–Ruvalcaba syndrome.

Carrier testing for Roberts syndrome requires prior identification of the disease-causing mutation in the family. Carriers for the disorder are heterozygotes due to the autosomal recessive nature of the disease. Carriers are also not at risk for contracting Roberts syndrome themselves. A prenatal diagnosis of Roberts syndrome requires an ultrasound examination paired with cytogenetic testing or prior identification of the disease-causing ESCO2 mutations in the family.

Diagnosis is made based on features as well as by the very early onset of serious eye and ear disease. Because Marshall syndrome is an autosomal dominant hereditary disease, physicians can also note the characteristic appearance of the biological parent of the child. There are no tests for Stickler syndrome or Marshall syndrome. Some families with Stickler syndrome have been shown to have mutations in the Type II collagen gene on chromosome 1. However, other families do not show the linkage to the collagen gene. It is an area of active research, also the genetic testing being expensive supports that the diagnosis is made depending on the features.

Cytogenetic preparations that have been stained by either Giemsa or C-banding techniques will show two characteristic chromosomal abnormalities. The first chromosomal abnormality is called premature centromere separation (PCS) and is the most likely pathogenic mechanism for Roberts syndrome. Chromosomes that have PCS will have their centromeres separate during metaphase rather than anaphase (one phase earlier than normal chromosomes). The second chromosomal abnormality is called heterochromatin repulsion (HR). Chromosomes that have HR experience separation of the heterochromatic regions during metaphase. Chromosomes with these two abnormalities will display a "railroad track" appearance because of the absence of primary constriction and repulsion at the heterochromatic regions. The heterochromatic regions are the areas near the centromeres and nucleolar organizers. Carrier status cannot be determined by cytogenetic testing. Other common findings of cytogenetic testing on Roberts syndrome patients are listed below.

- Aneuploidy- the occurrence of one or more extra or missing chromosomes

- Micronucleation- nucleus is smaller than normal

- Multilobulated Nuclei- the nucleus has more than one lobe

In terms of treatment/management one should observe what signs or symptoms are present and therefore treat those as there is no other current guideline. The affected individual should be monitored for cancer of:

- Thyroid

- Breast

- Renal

There is no medical treatment for either syndrome but there are some recommendations that can help with prevention or early identification of some of the problems. Children with either syndrome should have their hearing tested, and adults should be aware that the hearing loss may not develop until the adult years. Yearly visits to an ophthalmologist or other eye care professional who has been informed of the diagnosis of Stickler or Marshall syndrome is important for all affected individuals. Children should have the opportunity to have myopia corrected as early as possible, and treatment for cataracts or detached retinas may be more effective with early identification. Support for the joints is especially important during sports, and some recommend that contact sports should be avoided by those who have very loose joints.

Many professionals that are likely to be involved in the treatment of those with Stickler's syndrome, include anesthesiologists, oral and maxillofacial surgeons; craniofacial surgeons; ear, nose, and throat specialists, ophthalmologists, optometrists, audiologists, speech pathologists, physical therapists and rheumatologists.

In regards to the diagnosis of spinal and bulbar muscular atrophy, the "AR Xq12" gene is the focus. Many mutations are reported and identified as missense/nonsense, that can be identified with 99.9% accuracy. Test for this gene in the majority of affected patients yields the diagnosis.

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).

Prognoses for 3C syndrome vary widely based on the specific constellation of symptoms seen in an individual. Typically, the gravity of the prognosis correlates with the severity of the cardiac abnormalities. For children with less severe cardiac abnormalities, the developmental prognosis depends on the cerebellar abnormalities that are present. Severe cerebellar hypoplasia is associated with growth and speech delays, as well as hypotonia and general growth deficiencies.

Genetic changes are related to the following types of Stickler syndrome:

- Stickler syndrome, COL2A1 (75% of Stickler cases)

- Stickler syndrome, COL11A1

- Stickler syndrome, COL11A2 (non-ocular)

- Stickler syndrome, COL9A1 (recessive variant)

Whether there are two or three types of Stickler syndrome is controversial. Each type is presented here according to the gene involved. The classification of these conditions is changing as researchers learn more about the genetic causes.

In medicine a broad definition of syndrome is used, which describes a collection of symptoms and findings without necessarily tying them to a single identifiable pathogenesis. The more specific definition employed in medical genetics describes a subset of all medical syndromes.

A syndrome is a set of medical signs and symptoms occurring together, constitutes a particular disease or disorder. The word derives from the Greek σύνδρομον, meaning "concurrence". In some instances, a syndrome is so closely linked with a pathogenesis or cause that the words "syndrome", "disease", and "disorder" end up being used interchangeably for them. This is especially true of inherited syndromes. For example, Down syndrome, Wolf–Hirschhorn syndrome, and Andersen syndrome are disorders with known pathogeneses, so each is more than just a set of signs and symptoms, despite the "syndrome" nomenclature. In other instances, a syndrome is not specific to only one disease. For example, toxic shock syndrome can be caused by various toxins; premotor syndrome can be caused by various brain lesions; and premenstrual syndrome is not a disease but simply a set of symptoms.

If an underlying genetic cause is suspected but not known, a condition may be referred to as a genetic association (often just "association" in context). By definition, an association indicates that the collection of signs and symptoms occurs in combination more frequently than would be likely by chance alone.

Syndromes are often named after the physician or group of physicians that discovered them or initially described the full clinical picture. Such eponymous syndrome names are examples of medical eponyms. Recently, there has been a shift towards naming conditions descriptively (by symptoms or underlying cause) rather than eponymously, but the eponymous syndrome names often persist in common usage.

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)

At the 2005 American Society of Human Genetics meeting, Francis Collins gave a presentation about a treatment he devised for children affected by Progeria. He discussed how farnesyltransferase inhibitor (FTI) affects H-Ras. After his presentation, members of the Costello Syndrome Family Network discussed the possibility of FTIs helping children with Costello syndrome. Mark Kieran, who presented at the 1st International Costello Syndrome Research Symposium in 2007, agreed that FTIs might help children with Costello syndrome. He discussed with Costello advocates what he had learned in establishing and running the Progeria clinical trial with an FTI, to help them consider next steps.

Another medication that affects H-Ras is Lovastatin, which is planned as a treatment for neurofibromatosis type I. When this was reported in mainstream news, the Costello Syndrome Professional Advisory Board was asked about its use in Costello Syndrome. Research into the effects of Lovastatin was linked with Alcino Silva, who presented his findings at the 2007 symposium. Silva also believed that the medication he was studying could help children with Costello syndrome with cognition.

A third medication that might help children with Costello syndrome is a MEK inhibitor that helps inhibit the pathway closer to the cell nucleus.

According to the Williams Syndrome Association, diagnosis of Williams syndrome begins with recognition of physical symptoms and markers, which is followed by a confirmatory genetic test. The physical signs that often indicate a suspected case of Williams syndrome include puffiness around the eyes, a long philtrum, and a pattern in the iris. Physiological symptoms that often contribute to a Williams syndrome diagnosis are cardiovascular problems, particularly aortic or pulmonary stenosis, as well as feeding disturbance in infants. Developmental delays are often taken as an initial sign of the syndrome, as well.

If a physician suspects a case of Williams syndrome, the diagnosis is confirmed using one of two possible genetic tests: micro-array analysis or the fluorescent in situ hybridization (FISH) test. The FISH test examines chromosome #7 and probes for the existence of two copies of the elastin gene. Since 98-99% of individuals with Williams syndrome lack half of the 7q11.23 region of chromosome #7, where the elastin gene is located, the presence of only one copy of the gene is a strong sign of the syndrome. This confirmatory genetic test has been validated in epidemiological studies of the syndrome, and has been demonstrated to be a more effective method of identifying Williams syndrome than previous methods, which often relied on the presence of cardiovascular problems and facial features (which, while common, are not always present).

Some diagnostic studies suggest that reliance on facial features to identify Williams syndrome may cause a misdiagnosis of the condition. Among the more reliable features suggestive of Williams are congenital heart disease, periorbital fullness ("puffy" eyes), and the presence of a long smooth philtrum. Less reliable signs of the syndrome include anteverted nostrils, a wide mouth, and an elongated neck. Researchers indicate that even with significant clinical experience, it is difficult to reliably identify Williams syndrome based on facial features alone.

After the first discovery and description of Marshall–Smith syndrome in 1971, research to this rare syndrome has been carried out.

- Adam, M., Hennekam, R.C.M., Butler, M.G., Raf, M., Keppen, L., Bull, M., Clericuzio, C., Burke, L., Guttacher, A., Ormond, K., & Hoyme, H.E. (2002). Marshall–Smith syndrome: An osteochondrodysplasia with connective tissue abnormalities. 23rd Annual David W. Smith Workshop on Malformations and Morphogenesis, August 7, Clemson, SC.

- Adam MP, Hennekam RC, Keppen LD, Bull MJ, Clericuzio CL, Burke LW, Guttmacher AE, Ormond KE and Hoyme HE: Marshall-Smith Syndrome: Natural history and evidence of an osteochondrodysplasia with connective tissue abnormalities. American Journal of Medical Genetics 137A:117–124, 2005.

- Baldellou Vazquez A, Ruiz-Echarri Zelaya MP, Loris Pablo C, Ferr#{225}ndez Longas A, Tamparillas Salvador M. El sIndrome de Marshall-Smith: a prop#{243}sito de una observad#{243}n personal. An Esp Pediatr 1983; 18:45-50.

- Butler, M.G. (2003). Marshall–Smith syndrome. In: The NORD Guide to Rare Disorders. (pp219–220) Lippincott, Williams & Wilkins, Philadelphia, PA.

- Charon A, Gillerot T, Van Maldergem L, Van Schaftingen MH, de Bont B, Koulischer L. The Marshall–Smith syndrome. Eur J Pediatr 1990; 150: 54-5.

- Dernedde, G., Pendeville, P., Veyckemans, F., Verellen, G. & Gillerot, Y. (1998). Anaesthetic management of a child with Marshall–Smith syndrome. Canadian Journal of Anesthesia. 45 (7): 660. Anaesthetic management of a child with Marshall-Smith syndrome

- Diab, M., Raff, M., Gunther, D.F. (2002). Osseous fragility in Marshall–Smith syndrome. Clinical Report: Osseous fragility in Marshall-Smith syndrome

- Ehresmann, T., Gillessen-Kaesbach G., Koenig R. (2005). Late diagnosis of Marshall Smith Syndrome (MSS). In: Medgen 17.

- Hassan M, Sutton T, Mage K, LimalJM, Rappaport R. The syndrome of accelerated bone maturation in the newborn infant with dysmorphism and congenital malformations: (the so-called Marshall–Smith syndrome). Pediatr Radiol 1976; 5:53-57.

- Hoyme HE and Bull MJ: The Marshall-Smith Syndrome: Natural history beyond infancy. Western Society for Pediatric Research, Carmel, California, February, 1987. Clin Res 35:68A, 1987.

- Hoyme HE and Bull MJ: The Marshall-Smith Syndrome: Natural history beyond infancy. David W. Smith Morphogenesis and Malformations Workshop. Greenville, SC, August, 1987. Proceedings of the Greenwood Genetics Center 7:152, 1988.

- Hoyme HE, Byers PH, Guttmacher AE: Marshall–Smith syndrome: Further evidence of an osteochondrodysplasia in long-term survivors. David W. Smith Morphogenesis and Malformations Workshop, Winston-Salem, NC, August, 1992. Proceedings of the Greenwood Genetic Center 12:70, 1993.

- .

- Tzu-Jou Wang (2002). Marshall–Smith syndrome in a Taiwanese patient with T-cell immunodeficiency. Am J Med Genet Part A;112 (1):107-108.

A typical method for determining the effects of the sopite syndrome is through the use of one or several questionnaires. The available questionnaires for motion sickness and sopite syndrome are described by Lawson. Two such questionnaires widely used to evaluate motion sickness are the Pensacola Diagnostic Index and the Motion Sickness Questionnaire. These questionnaires are limited, however, in that they group symptoms of drowsiness with other non-sopite related effects, such as nausea and dizziness. Motion sickness is measured based on the cumulative ratings of all these symptoms without distinguishing different levels for each effect.

A Motion Sickness Assessment Questionnaire has been developed to test the multiple dimensions of motion sickness more thoroughly; this survey defines motion sickness as gastrointestinal (involving nausea), peripheral (referring to thermoregulatory effects such as clamminess and sweating), central (involving symptoms such as dizziness and lightheadedness), and sopite-related. This questionnaire may more accurately determine how subjects experience sopite symptoms relative to other motion sickness effects. Another questionnaire designed to measure sleepiness is the Epworth Sleepiness Scale.

The outcome of this disease is dependent on the severity of the cardiac defects. Approximately 1 in 3 children with this diagnosis require shunting for the hydrocephaly that is often a consequence. Some children require extra assistance or therapy for delayed psychomotor and speech development, including hypotonia.

Pashayan syndrome also known as Pashayan–Prozansky Syndrome, and blepharo-naso-facial syndrome is a rare syndrome. Facial abnormalities characterise this syndrome as well as malformation of extremities. Specific characteristics would be a bulky, flattened nose, where the face has a mask like appearance and the ears are also malformed.

A subset of Pashayan syndrome has also been described, known as "cerebrofacioarticular syndrome", "Van Maldergem syndrome'" or "Van Maldergem–Wetzburger–Verloes syndrome". Similar symptoms are noted in these cases as in Pashayan syndrome.

The sopite syndrome may be difficult to test due to the nature of the symptoms. Indicators such as drowsiness, mood changes, and apathy must be observed and graded objectively. Therefore, many of the results obtained from studies of the sopite syndrome are not sufficiently repeatable for the purposes of scientific writing.

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.

Nevo Syndrome is considered to be a rare disorder. Since its first appearance in 1974, only a handful of cases have been reported. Studies have shown showing similarities between Nevo Syndrome with Ehlers-Danlos syndrome as well as Sotos syndrome. There is an astounding overlap of phenotypic manifestations between Nevo Syndrome and the more frequent Sotos syndrome, which are both caused by the NSD1 deletion. Sotos syndrome is an autosomal dominant condition associated with learning disabilities, a distinctive facial appearance, and overgrowth. Studies have shown an overwhelming occurrence (half of those involved in the study) of Nevo syndrome in those individuals of Middle-Eastern descent.