Juvenile myoclonic epilepsy is an inherited genetic syndrome, but the way in which this disorder is inherited is unclear. Frequently (17-49%) those with JME have relatives with a history of epileptic seizures. It is currently unclear if JME is more common in males or females. Almost all cases of JME, however, have an onset in early childhood to puberty.

Juvenile myoclonic epilepsy (JME), also known as Janz syndrome, is a fairly common form of idiopathic generalized epilepsy, representing 5-10% of all epilepsy cases. This disorder typically first manifests itself between the ages of 12 and 18 with brief episodes of involuntary muscle twitching occurring early in the morning. Most patients also have generalized seizures that affect the entire brain and many also have absence seizures. Genetic studies have demonstrated at least 6 loci for JME, 4 with known causative genes.

Most of these genes are ion channels with the one non-ion channel gene having been shown to affect ion channel currents.

It is not possible to make a generalised prognosis for development due to the variability of causes, as mentioned above, the differing types of symptoms and cause. Each case must be considered individually.

The prognosis for children with idiopathic West syndrome are mostly more positive than for those with the cryptogenic or symptomatic forms. Idiopathic cases are less likely to show signs of developmental problems before the attacks begin, the attacks can often be treated more easily and effectively and there is a lower relapse rate. Children with this form of the syndrome are less likely to go on to develop other forms of epilepsy; around two in every five children develop at the same rate as healthy children.

In other cases, however, treatment of West syndrome is relatively difficult and the results of therapy often dissatisfying; for children with symptomatic and cryptogenic West syndrome, the prognosis is generally not positive, especially when they prove resistant to therapy.

Statistically, 5 out of every 100 children with West syndrome do not survive beyond five years of age, in some cases due to the cause of the syndrome, in others for reasons related to their medication. Only less than half of all children can become entirely free from attacks with the help of medication. Statistics show that treatment produces a satisfactory result in around three out of ten cases, with only one in every 25 children's cognitive and motoric development developing more or less normally.

A large proportion (up to 90%) of children suffer severe physical and cognitive impairments, even when treatment for the attacks is successful. This is not usually because of the epileptic fits, but rather because of the causes behind them (cerebral anomalies or their location or degree of severity). Severe, frequent attacks can (further) damage the brain.

Permanent damage often associated with West syndrome in the literature include cognitive disabilities, learning difficulties and behavioural problems, cerebral palsy (up to 5 out of 10 children), psychological disorders and often autism (in around 3 out of 10 children). Once more, the cause of each individual case of West syndrome must be considered when debating cause and effect.

As many as 6 out of 10 children with West syndrome suffer from epilepsy later in life. Sometimes West syndrome turns into a focal or other generalised epilepsy. Around half of all children develop Lennox-Gastaut syndrome.

Incidence is around 1:3200 to 1:3500 of live births. Statistically, boys are more likely to be affected than girls at a ratio of around 1.3:1. In 9 out of every 10 children affected, the spasms appear for the first time between the third and the twelfth month of age. In rarer cases, spasms may occur in the first two months or during the second to fourth year of age.

Generalized epilepsy with febrile seizures plus (GEFS+) is an umbrella for many other syndromes that share causative genes. Patients experience febrile seizures early in childhood and grow to experience other types of seizures later in life. Known causative genes for GEFS+ are the sodium channel α subunit genes SCN1A and SCN2A and the β subunit gene SCN1B. Mutations in the GABA receptor γ subunit GABRG1 are also causative for this disorder.

This form of epilepsy is very rare, representing less than 1% of cases, and is twice as prevalent in boys compared to girls. Age of seizure onset is between 5 months and 5 years of age. Children with this disorder often present with head drops and brief arm jerks. Although there is believed to be a genetic basis for this disorder, no genetic linkage has been shown.

Pisa syndrome is predominantly caused by a prolonged administration or an overly dosed administration of antipsychotic drugs. Although antipsychotic drugs are known to be the main drugs that are concerned with this syndrome, several other drugs are reported to have caused the syndrome as well. Certain antidepressants, psychoactive drugs, and antiemetics have also been found to cause Pisa syndrome in patients.

Drugs found to have caused Pisa Syndrome:

- Atypical antipsychotic drugs- ex. clozapine, aripiprazole

- Tricyclic antidepressants- ex. clomipramine

- Psychoactive drugs

- Antiemetic drugs

- Cholinesterase inhibitors

- Galantamine

Based on the drugs that caused Pisa syndrome, it has been implicated that the syndrome may be due to a dopaminergic-cholinergic imbalance or a serotonergic or noradrenergic dysfunction. For the development of Pisa syndrome that cannot be alleviated by anticholinergic drugs, it has been considered that asymmetric brain functions or neural transmission may be the underlying mechanism. How these drugs interact with the biochemistry of the brain to cause the syndrome is unknown and a topic of current research.

Typically, females and older patients with organic brain changes are more likely to develop Pisa syndrome. Organic brain changes are physical changes in the brain which lead to neurological dysfunction, including dementia and frontal lobe syndrome. This includes the presence of neurodegenerative illnesses such as Alzheimer's Disease and Parkinson's Disease.

The prognosis varies widely from case to case, depending on the severity of the symptoms. However, almost all people reported with Aicardi syndrome to date have experienced developmental delay of a significant degree, typically resulting in mild to moderate to profound intellectual disability. The age range of the individuals reported with Aicardi syndrome is from birth to the mid 40s.

There is no cure for this syndrome.

Worldwide prevalence of Aicardi Syndrome is estimated at several thousand, with approximately 900 cases reported in the United States.

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.

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.

At this time, there are no other phenotypes (observable expressions of a gene) that have been discovered for mutations in the ESCO2 gene.

The prognosis for patients diagnosed with Timothy syndrome is very poor. Of 17 children analyzed in one study, 10 died at an average age of 2.5 years. Of those that did survive, 3 were diagnosed with autism, one with an autism spectrum disorder, and the last had severe delays in language development. One patient with atypical Timothy syndrome was largely normal with the exception of heart arrhythmia. Likewise, the mother of two Timothy syndrome patients also carried the mutation but lacked any obvious phenotype. In both of these cases, however, the lack of severity of the disorder was due to mosaicism.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

Rotor syndrome, also called Rotor type hyperbilirubinemia, is a rare, relatively benign autosomal recessive bilirubin disorder. It is a distinct, yet similar disorder to Dubin–Johnson syndrome — both diseases cause an increase in conjugated bilirubin.

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.

Nevo Syndrome is an autosomal recessive disorder. Most times in which a child is afflicted with Nevo Syndrome, both their parents are of average height and weight. It is only until after birth when the characteristic physical traits associated with disease are manifested, and the disorder is actually diagnosed. One study showed that despite the increased growth rates, the patient was completely healthy up until age 6, when he was admitted into the hospital. Nevo syndrome is usually associated with early childhood fatality. Children with Nevo Syndrome have a high occurrence of death due to cardiac arrest because their developing hearts cannot keep up with their overgrown body.

In mild cases, individuals with XXXY syndrome may lead a relatively good life. These individuals may face difficulties in communicating with others due to their language-based deficits. These deficits may make forming bonds with others difficult, but fulfilling relationships with others are still achievable. Those with higher scores in adaptive functioning are likely to have higher quality of life because they can be independent.

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.

One possible cause of Harlequin syndrome is a lesion to the preganglionic or postganglionic cervical sympathetic fibers and parasympathetic neurons of the ciliary ganglion. It is also believed that torsion (twisting) of the thoracic spine can cause blockage of the anterior radicular artery leading to Harlequin syndrome. The sympathetic deficit on the denervated side causes the flushing of the opposite side to appear more pronounced. It is unclear whether or not the response of the undamaged side was normal or excessive, but it is believed that it could be a result of the body attempting to compensate for the damaged side and maintain homeostasis.

Since the cause and mechanism of Harlequin syndrome is still unknown, there is no way to prevent this syndrome.

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.

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.

Timothy syndrome is a rare autosomal dominant disorder characterized by physical malformations, as well as neurological and developmental defects, including heart QT-prolongation, heart arrhythmias, structural heart defects, syndactyly (webbing of fingers and toes) and autism spectrum disorders.

Timothy syndrome often ends in early childhood death.

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.