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.

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

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

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- 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.

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Even in syndromes with no known etiology, the presence of the associated symptoms with a statistically improbable correlation, normally leads the researchers to hypothesize that there exists an unknown underlying cause for all the described symptoms.

Harlequin syndrome is not debilitating so treatment is not normally necessary. In cases where the individual may feel socially embarrassed, contralateral sympathectomy may be considered, although compensatory flushing and sweating of other parts of the body may occur. In contralateral sympathectomy, the nerve bundles that cause the flushing in the face are interrupted. This procedure causes both sides of the face to no longer flush or sweat. Since symptoms of Harlequin syndrome do not typically impair a person’s daily life, this treatment is only recommended if a person is very uncomfortable with the flushing and sweating associated with the syndrome.

Secretan’s syndrome is a rare condition of hard edema and traumatic hyperplasia of the dorsum of the hand. Most expert view it as a self-inflicted condition.

It was first described in 1901 by Henri-François Secretan, a Swiss insurance physician. He described a condition characterized by a hard, sometimes cyanotic edema (Charcot's blue edema) on the dorsal aspect of the hand.

This condition which some people think is a self-inflicted (factitious) condition usually starts with a small accidental injury of the dorsum of the hand. This is usually followed by swelling edema and cyanosis of the dorsum of the usually right hand.

The edema is thought to be secondary to excessive inflammation the condition slowly burns out with the edema being replaced by fibrosis surrounding the extensor tendons of the hand.

As there is no known cure, Loeys–Dietz syndrome is a lifelong condition. Due to the high risk of death from aortic aneurysm rupture, patients should be followed closely to monitor aneurysm formation, which can then be corrected with interventional radiology or vascular surgery.

Previous research in laboratory mice has suggested that the angiotensin II receptor antagonist losartan, which appears to block TGF-beta activity, can slow or halt the formation of aortic aneurysms in Marfan syndrome. A large clinical trial sponsored by the National Institutes of Health is currently underway to explore the use of losartan to prevent aneurysms in Marfan syndrome patients. Both Marfan syndrome and Loeys–Dietz syndrome are associated with increased TGF-beta signaling in the vessel wall. Therefore, losartan also holds promise for the treatment of Loeys–Dietz syndrome. In those patients in which losartan is not halting the growth of the aorta, irbesartan has been shown to work and is currently also being studied and prescribed for some patients with this condition.

If an increased heart rate is present, atenolol is sometimes prescribed to reduce the heart rate to prevent any extra pressure on the tissue of the aorta. Likewise, strenuous physical activity is discouraged in patients, especially weight lifting and contact sports.

In the United States, sarcoidosis has a prevalence of approximately 10 cases per 100,000 whites and 36 cases per 100,000 blacks. Heerfordt syndrome is present in 4.1–5.6% of those with sarcoidosis.

In August 2016, researchers at the Instituto de Assistência dos Servidores do Estado do Rio de Janeiro used botulinum toxin as a method to block the acetylcholine release from the presynaptic neurons. Although they have seen a reduction in one sided flushing, sweating still occurs.

There have been case studies of individuals whom have experienced this syndrome after an operation. Two patients, a 37-year-old and 58-year-old female patients suffering from metastatic cancer were scheduled for placement of an intrathecal pump drug delivery system. After the intrathecal pump was placed, certain medications were given to the patients. Once the medications were administered, both patients had one sided facial flushes, closely resembling Harlequin Syndrome. Patients were given neurological exams to confirm that their nerves were still intact. An MRI was performed and showed no significant evidence of bleeding or nerve compression. After close observation for 16 hours, symptoms of the Harlequin syndrome was diminished and both patients did not have another episode.

Another case study was based on a 6-year-old male visiting an outpatient setting for one sided flushes during or after physical activity or exposed to heat. Vitals, laboratory tests, and CT scans were normal. Along with the flushes, the right pupil was 1.5 mm in size, while the left pupil was 2.5 mm in size; however, no ptosis, miosis, or enophthalmos was noted. The patient also had an MRI scan to rule out any lesion near the brain or spinal cord. No abnormalities were noted and the patient did not receive any treatments. The patient was diagnosed with idiopathic Harlequin syndrome.

Although the mechanism is still unclear, the pathophysiology of this condition, close monitoring, and reassurance are vital factors for successful management.

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)

There is an association between taking aspirin for viral illnesses and the development of Reye syndrome, but no animal model of Reye syndrome has been developed in which aspirin causes the condition.

The serious symptoms of Reye syndrome appear to result from damage to cellular mitochondria, at least in the liver, and there are a number of ways that aspirin could cause or exacerbate mitochondrial damage. A potential increased risk of developing Reye syndrome is one of the main reasons that aspirin has not been recommended for use in children and teenagers, the age group for which the risk of lasting serious effects is highest.

No research has found a definitive cause of Reye syndrome, and association with aspirin has been shown through epidemiological studies. The diagnosis of "Reye Syndrome" greatly decreased in the 1980s, when genetic testing for inborn errors of metabolism was becoming available in developed countries. A retrospective study of 49 survivors of cases diagnosed as "Reye's Syndrome" showed that the majority of the surviving patients had various metabolic disorders, particularly a fatty-acid oxidation disorder medium-chain acyl-CoA dehydrogenase deficiency.

In some countries, oral mouthcare product Bonjela (not the form specifically designed for teething) has labeling cautioning against its use in children, given its salicylate content. There have been no cases of Reye syndrome following its use, and the measure is a precaution. Other medications containing salicylates are often similarly labeled as a precaution.

The Centers for Disease Control and Prevention (CDC), the U.S. Surgeon General, the American Academy of Pediatrics (AAP) and the Food and Drug Administration (FDA) recommend that aspirin and combination products containing aspirin not be given to children under 19 years of age during episodes of fever-causing illnesses. Hence, in the United States, it is advised that the opinion of a doctor or pharmacist should be obtained before anyone under 19 years of age is given any medication containing aspirin (also known on some medicine labels as acetylsalicylate, salicylate, acetylsalicylic acid, ASA, or salicylic acid).

Current advice in the United Kingdom by the Committee on Safety of Medicines is that aspirin should not be given to those under the age of 16 years, unless specifically indicated in Kawasaki disease or in the prevention of blood clot formation.

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.

As of 2017, data on optimal treatment was limited. Therapies with hormones is the standard of care, namely adrenocorticotrophic hormone (ACTH), or oral

corticosteroids such as prednisone. Vigabatrin is also a common consideration, though there is a risk of visual field loss with long term use. The high cost of ACTH leads doctors to avoid it in the US; higher dose prednisone appears to generate equivalent outcomes.

As of 2017 data from clinical trials of the ketogenic diet for treating infantile spams was inconsistent; most trials were as a second-line therapy after failure of drug treatment, and as of 2017 it had not been explored as a first line treatment in an adequately designed clinical trial.

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.

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.

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

Medical management of children with Trisomy 13 is planned on a case-by-case basis and depends on the individual circumstances of the patient. Treatment of Patau syndrome focuses on the particular physical problems with which each child is born. Many infants have difficulty surviving the first few days or weeks due to severe neurological problems or complex heart defects. Surgery may be necessary to repair heart defects or cleft lip and cleft palate. Physical, occupational, and speech therapy will help individuals with Patau syndrome reach their full developmental potential. Surviving children are described as happy and parents report that they enrich their lives. The cited study grouped Edwards syndrome, which is sometimes survivable beyond toddlerhood, along with Patau, hence the median age of 4 at the time of data collection.

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.

Treatment of Aicardi syndrome primarily involves management of seizures and early/continuing intervention programs for developmental delays.

Additional comorbidities and complications sometimes seen with Aicardi syndrome include porencephalic cysts and hydrocephalus, and gastro-intestinal problems. Treatment for porencephalic cysts and/or hydrocephalus is often via a shunt or endoscopic of the cysts, though some require no treatment. Placement of a feeding tube, fundoplication, and surgeries to correct hernias or other gastrointestinal structural problems are sometimes used to treat gastro-intestinal issues.

More than 80% of children with Patau syndrome die within the first year of life. Children with the mosaic variation are usually affected to a lesser extent. In a retrospective Canadian study of 174 children with trisomy 13, median survival time was 12.5 days. One and ten year survival was 19.8% and 12.9% respectively.

The Kocher–Debré–Semelaigne syndrome is hypothyroidism in infancy or childhood characterised by lower extremity or generalized muscular hypertrophy, myxoedema, short stature and cretinism. The absence of painful spasms and pseudomyotonia differentiates this syndrome from its adult form, which is Hoffmann syndrome.

The syndrome is named after Emil Theodor Kocher, Robert Debré and Georges Semelaigne.

Also known as Debre–Semelaigne syndrome or cretinism-muscular hypertrophy, hypothyroid myopathy, hypothyroidism-large muscle syndrome, hypothyreotic muscular hypertrophy in children, infantile myxoedema-muscular hypertrophy, myopathy-myxoedema syndrome, myxoedema-muscular hypertrophy syndrome, myxoedema-myotonic dystrophy syndrome.

Kocher-Debre-Semelaigne syndrome gives infant a Hercules appearance.

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.

There is no cure for Williams syndrome. Suggestions include avoidance of extra calcium and vitamin D, as well as treating high levels of blood calcium. Blood vessel narrowing can be a significant health problem, and is treated on an individual basis.

Physical therapy is helpful to patients with joint stiffness and low muscle tone. Developmental and speech therapy can also help children and increase the success of their social interactions. Other treatments are based on a patient's particular symptoms.

The American Academy of Pediatrics recommends annual cardiology evaluations for individuals with Williams syndrome. Other recommended assessments include: ophthalmologic evaluations, an examination for inguinal hernia, objective hearing assessment, blood pressure measurement, developmental and growth evaluation, orthopedic assessments on joints, muscle tone, and ongoing feeding and dietary assessments to manage constipation and urinary problems.

Behavioral treatments have been shown to be effective. In regards to social skills it may be effective to channel their nature by teaching basic skills. Some of these are the appropriate way to approach someone, how and when to socialize in settings such as school or the workplace, and warning of the signs and dangers of exploitation. For the fear that they demonstrate cognitive-behavioral approaches, such as therapy, are the recommended treatment. One of the things to be careful of with this approach is to make sure that the patients' charming nature does not mask any underlying feelings.

Perhaps the most effective treatment for those with Williams syndrome is music. Those with Williams syndrome have shown a relative strength in regards to music, albeit only in pitch and rhythm tasks. Not only do they show a strength in the field but also a particular fondness for it. It has been shown that music may help with the internal and external anxiety that these people are more likely to be afflicted with. Something of note is that the typical person processes music in the superior temporal and middle temporal gyri. Those with Williams syndrome have a reduced activation in these areas but an increase in the right amygdala and cerebellum.

People affected by Williams syndrome are supported by multiple organizations, including the Canadian Association for Williams Syndrome and the Williams Syndrome Registry.

Treatment of Roberts syndrome is individualized and specifically aimed at improving the quality of life for those afflicted with the disorder. Some of the possible treatments include: surgery for the cleft lip and palate, correction of limb abnormalities (also through surgery), and improvement in prehensile hand grasp development.

Documented cases of Reye syndrome in adults are rare. The recovery of adults with the syndrome is generally complete, with liver and brain function returning to normal within two weeks of onset. In children, however, mild to severe permanent brain damage is possible, especially in infants. Over thirty percent of the cases reported in the United States from 1981 through 1997 resulted in fatality.

If a contracture is less than 30 degrees, it may not interfere with normal functioning. The common treatment is splinting and occupational therapy. Surgery is the last option for most cases as the result may not be satisfactory.