PME accounts for less than 1% of epilepsy cases at specialist centres. The incidence and prevalence of PME is unknown, but there are considerable geography and ethnic variations amongst the specific genetic disorders. One cause, Unverricht Lundborg Disease, has an incidence of at least 1:20,000 in Finland.

The only country that Unverricht–Lundborg disease has a reported incidence is in Finland, where it is reported to occur in 4 in 100,000 individuals. However, ULD has only become well defined recently, and it is likely still under diagnosed, so the actual incidence may be different that what is currently known. Other countries with known cases include countries in the Mediterranean region including Italy, France, Tunisia, Algeria, and Morocco, as well as the United States.

For early Unverricht–Lundborg disease patients, the disease would begin to progress early and lack of effective treatment meant a quick progression. In many cases the patient would require a wheelchair for mobility, and would die at a young age.

However, increased knowledge about the disease and improved treatment and medication has led to a dramatic improvement in prognosis for individuals with ULD. Antiepileptic drugs reduce the occurrence of seizures and myoclonus, which leads to a decrease in the damage caused in the brain due to seizures and the body due to falls resulting from the seizures. As a result, individuals with Unverricht–Lundborg disease are now much less likely to end up in a wheelchair, which eliminates the chance of complications involved with being a wheelchair user. All these factors have increased the outlook for patients. Due to the progressive nature of the disease, depression is prevalent, but support of family and friends as well as proper treatment can help. While early patients with ULD had a life expectancy of around 24 years, there have recently been reported cases of individuals living to near-normal ages.

This is an autosomal recessive disorder in which the body is deficient in α-neuraminidase.

Cases of epilepsy may be organized into epilepsy syndromes by the specific features that are present. These features include the age at which seizures begin, the seizure types, and EEG findings, among others. Identifying an epilepsy syndrome is useful as it helps determine the underlying causes as well as what anti-seizure medication should be tried.

The ability to categorize a case of epilepsy into a specific syndrome occurs more often with children since the onset of seizures is commonly early. Less serious examples are benign rolandic epilepsy (2.8 per 100,000), childhood absence epilepsy (0.8 per 100,000) and juvenile myoclonic epilepsy (0.7 per 100,000). Severe syndromes with diffuse brain dysfunction caused, at least partly, by some aspect of epilepsy, are also referred to as epileptic encephalopathies. These are associated with frequent seizures that are resistant to treatment and severe cognitive dysfunction, for instance Lennox-Gastaut syndrome and West syndrome.

Epilepsies with onset in childhood are a complex group of diseases with a variety of causes and characteristics. Some people have no obvious underlying neurological problems or metabolic disturbances. They may be associated with variable degrees of intellectual disability, elements of autism, other mental disorders, and motor difficulties. Others have underlying inherited metabolic diseases, chromosomal abnormalities, specific eye, skin and nervous system features, or malformations of cortical development. Some of these epilepsies can be categorized into the traditional epilepsy syndromes. Furthermore, a variety of clinical syndromes exist of which the main feature is not epilepsy but which are associated with a higher risk of epilepsy. For instance between 1 and 10% of those with Down syndrome and 90% of those with Angelman syndrome have epilepsy.

In general, genetics is believed to play an important role in epilepsies by a number of mechanisms. Simple and complex modes of inheritance have been identified for some of them. However, extensive screening has failed to identify many single rare gene variants of large effect. In the epileptic encephalopathies, de novo mutagenesis appear to be an important mechanism. De novo means that a child is affected, but the parents do not have the mutation. De novo mutations occur in eggs and sperms or at a very early stage of embryonic development. In Dravet syndrome a single affected gene was identified.

Syndromes in which causes are not clearly identified are difficult to match with categories of the current classification of epilepsy. Categorization for these cases is made somewhat arbitrarily. The "idiopathic" (unknown cause) category of the 2011 classification includes syndromes in which the general clinical features and/or age specificity strongly point to a presumed genetic cause. Some childhood epilepsy syndromes are included in the unknown cause category in which the cause is presumed genetic, for instance benign rolandic epilepsy. Others are included in "symptomatic" despite a presumed genetic cause (in at least in some cases), for instance Lennox-Gastaut syndrome. Clinical syndromes in which epilepsy is not the main feature (e.g. Angelman syndrome) were categorized "symptomatic" but it was argued to include these within the category "idiopathic". Classification of epilepsies and particularly of epilepsy syndromes will change with advances in research.

West syndrome is a triad of developmental delay, seizures termed infantile spasms, and EEG demonstrating a pattern termed hypsarrhythmia. Onset occurs between three months and two years, with peak onset between eight and 9 months. West syndrome may arise from idiopathic, symptomatic, or cryptogenic causes. The most common cause is tuberous sclerosis. The prognosis varies with the underlying cause. In general, most surviving patients remain with significant cognitive impairment and continuing seizures and may evolve to another eponymic syndrome, Lennox-Gastaut syndrome. It can be classified as idiopathic, syndromic, or cryptogenic depending on cause and can arise from both focal or generalized epileptic lesions.

Progressive myoclonus epilepsy is a disease associated with myoclonus, epileptic seizures, and other problems with walking or speaking. These symptoms often worsen over time and can be fatal.

MERRF syndrome is also known as myoclonic epilepsy with ragged-red fibers. This rare inherited disorder affects muscles cells. Features of MERRF, along with myoclonus epilepsy seizures, include ataxia, peripheral neuropathy, and dementia.

Lafora disease is also known as Lafora progressive myoclonus epilepsy, which is an autosomal recessive inherited disorder involving recurrent seizures and degradation of mental capabilities. Lafora disease usually occurs in late childhood and usually leads to death around 10 years after first signs of the disease.

Unverricht-Lundborg disease is an autosomal recessive inherited disorder seen in individuals as young as six years. It is associated with possible loss of consciousness, rigidity, ataxia, dysarthria, declination of mental functioning, and involuntary shaking.

Neuronal ceroid lipofuscinosis is a group of diseases that cause blindness, loss of mental abilities, and loss of movement. All diseases in this group are lysosomal-storage disorders that also lead to death roughly ten years after onset of the disease.

Myoclonic epilepsy refers to a family of epilepsies that present with myoclonus. When myoclonic jerks are occasionally associated with abnormal brain wave activity, it can be categorized as myoclonic seizure. If the abnormal brain wave activity is persistent and results from ongoing seizures, then a diagnosis of myoclonic epilepsy may be considered.

There are multiple symptoms that can help this disease to be diagnosed, this disease is marked by the presence of acanthocytes in blood (these acanthocytes can sometimes be absent or even make a late appearance in the course of the disease.) and neurodegeneration causing a choreiform movement disorder.

Another one of them would be that this disease should be considered in patients who have elevated levels of acanthocytes in a peripheral blood film.

The serum creatine kinase is often elevated in the body of the people who are affected by this disease.

People afflicted by this disease also experience a loss of neurons. Loss of neurons is a hallmark of neurodegenerative diseases. Due to the generally non-regenerative nature of neuronal cells in the adult central nervous system, this results in an irreversible and fatal process of neurodegeneration. There is also the presence of several movement related disorders including chorea, dystonia and bradykinesia, one of the more incapacitating ones includes Truncal spasms.

The treatment to battle the disease chorea-acanthocytosis is completely symptomatic. For example, Botulinum toxin injections can help to control orolingual dystonia.

Deep Brain Stimulation is a treatment that has varied effects on the people suffering from the symptoms of this disease, for some it has helped in a large way and for other people it did not help whatsoever, it is more effective on specific symptoms of the disease. Patients with chorea-acanthocytosis should undergo a cardiac evaluation every 5 years to look for cardiomyopathy.

Batten disease is a fatal disease of the nervous system that typically begins in childhood. Onset of symptoms is usually between 5 and 10 years of age. Often it is autosomal recessive. It is the most common form of a group of disorders called the neuronal ceroid lipofuscinoses (NCLs).

Although Batten disease is usually regarded as the juvenile form of NCL (or "type 3"), some physicians use the term Batten disease to describe all forms of NCL. Historically, the NCLs were classified by age of disease onset as infantile NCL (INCL), late infantile NCL (LINCL), juvenile NCL (JNCL) or adult NCL (ANCL). At least 20 genes have been identified in association with Batten disease, but juvenile NCL, the most prevalent form of Batten disease, has been linked to mutations in the "CLN3" gene.

It was first described in 1903.

In infantile Krabbe disease, death usually occurs in early childhood. A 2011 study found 1, 2, 3 year survival rates of 60%, 26%, and 14%, respectively. A few survived for longer and one was still alive at age 13. Patients with late-onset Krabbe disease tend to have a slower progression of the disease and live significantly longer.

Batten disease is a terminal illness; the FDA has approved Brineura (cerliponase alfa) as a treatment for a specific form of Batten disease. Brineura is the first FDA-approved treatment to slow loss of walking ability (ambulation) in symptomatic pediatric patients 3 years of age and older with late infantile neuronal ceroid lipofuscinosis type 2 (CLN2), also known as tripeptidyl peptidase-1 (TPP1) deficiency. Palliative treatment is symptomatic and supportive.

Krabbe disease occurs in about one in 100,000 births. A higher incidence, about six in 1,000, has been reported in certain communities in Israel. Scandinavian countries have comparatively high rates of the disease, reported to be one in 50,000 births.

Sandhoff disease can be detected through the following procedures (before it is apparent through physical examination): a biopsy removing a sample of tissue from the liver, genetic testing, molecular analysis of cells and tissues (to determine the presence of a genetic metabolic disorder), enzyme assay, and occasionally a urinalysis to determine if the above-noted compounds are abnormally stored within the body. For a child to suffer from this disease, both parents must be carriers, and both must transmit the mutation to the child. Thus, even in the case where both parents have the mutation, there is only a 25 percent chance their child will inherit the condition. Frequently, parents are given the opportunity to have a DNA screening if they are at high risk, to determine their carrier status before they have children. However, it is also highly recommended to undergo testing even for those parents who do not have a family history of Sandhoff disease. Over 95% of the families that have children with Sandhoff disease had no known prior family history of the condition, as the mutation in the HEXB gene is "silent," or recessive, and often passed undetected from one generation to the next Naturally, if an individual carries the mutation, he or she has a risk of transmitting it to the unborn child. Genetic counseling is recommended for those who have the mutation.

The most well known laboratory to perform the blood tests is through Lysosomal Diseases Testing Laboratory, Jefferson University with Dr. Wenger. Dr. Wenger’s laboratory does testing for all lysosomal diseases including Sandhoff and Tay-Sachs. They test for build-up of certain toxins in the body as well as a low count of enzymes.

It is possible for parents who are about to have a child or had a child with Sandhoff Disease can have a PGD or PEGD. PEGD is pre-embryonic genetic diagnosis for the parents that would not benefit from a pre-implantation genetic diagnosis because of their religion or negative attitude for the discarding of embryos. PEGD sequences the genome of the embryo to be produced by two parents if they were to conceive a child. If the family has a history of Sandhoff disease it is recommended they have their genome sequenced to ensure they are not carriers or to sequence the genome of their child.

There are three types of Sandhoff disease: classic infantile, juvenile, and adult late onset. Each form is classified by the severity of the symptoms as well as the age at which the patient shows these symptoms.

- Classic infantile form of the disease is classified by the development of symptoms anywhere from 2 months to 9 months of age. It is the most severe of all of the forms and will lead to death before the patient reaches the age of three. This is the most common and severe form of Sandhoff disease. Infants with this disorder typically appear normal until the age of 3 to 6 months, when development slows and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. As the disease progresses, infants develop seizures, vision and hearing loss, dementia, and paralysis. An eye abnormality called a cherry-red spot, which can be identified with an eye examination, is characteristic of this disorder. Some infants with Sandhoff disease may have enlarged organs (organomegaly) or bone abnormalities. Children with the severe form of this disorder usually live only into early childhood.

- Juvenile form of the disease shows symptoms starting at age 3 ranging to age 10 and, although the child usually dies by the time they are 15, it is possible for them to live longer if they are under constant care. Symptoms include autism, ataxia, motor skills regression, spacticity, and learning disorders.

- Adult onset form of the disease is classified by its occurrence in older individuals and has an effect on the motor function of these individuals. It is not yet known if Sandhoff disease will cause these individuals to have a decrease in their life span.

Juvenile and adult onset forms of Sandhoff disease are very rare. Signs and symptoms can begin in childhood, adolescence, or adulthood and are usually milder than those seen with the infantile form of Sandhoff disease. As in the infantile form, mental abilities and coordination are affected. Characteristic features include muscle weakness, loss of muscle coordination (ataxia) and other problems with movement, speech problems, and mental illness. These signs and symptoms vary widely among people with late-onset forms of Sandhoff disease.

It is associated with LAMP2. The status of this condition as a GSD has been disputed.

Infants with Schindler disease tend to die within 4 years of birth, therefore, treatment for this form of the disease is mostly palliative. However, Type II Schindler disease, with its late onset of symptoms, is not characterized by neurological degeneration. There is no known cure for Schindler disease, but bone marrow transplants have been trialed, as they have been successful in curing other glycoprotein disorders.

Most children with Farber disease die by age 2, usually from lung disease. In one of the most severe forms of the disease, an enlarged liver and spleen (hepatosplenomegaly) can be diagnosed soon after birth. Children born with this form of the disease usually die within 6 months.

Urbach–Wiethe disease is very rare; there are fewer than 300 reported cases in medical literature. Although Urbach–Wiethe disease can be found worldwide, almost a quarter of reported diagnoses are in South Africa. Many of these are in patients of Dutch, German, and Khoisan ancestry. This high frequency is thought to be due to the founder effect. Due to its recessive genetic cause and the ability to be a carrier of the disease without symptoms, Urbach–Wiethe disease often runs in families. In some regions of South Africa, up to one in 12 individuals may be carriers of the disease. Most of the case studies involving Urbach–Wiethe disease patients involve only one to three cases and these cases are often in the same family. Due to its low incidence, it is difficult to find a large enough number of cases to adequately study the disease.

Although the genetic cause of Danon Disease is known, the mechanism of disease is not well understood. Danon disease involves a genetic defect (mutation) in a gene called LAMP2, which results in a change to the normal protein structure. While the function of the "LAMP2" gene is not well understood, it is known that LAMP2 protein is primarily located in small structures within cells called lysosomes.

Schindler disease, also known as Kanzaki disease and alpha-N-acetylgalactosaminidase deficiency is a rare disease found in humans. This lysosomal storage disorder is caused by a deficiency in the enzyme alpha-NAGA (alpha-N-acetylgalactosaminidase), attributable to mutations in the NAGA gene on chromosome 22, which leads to excessive lysosomal accumulation of glycoproteins. A deficiency of the alpha-NAGA enzyme leads to an accumulation of glycosphingolipids throughout the body. This accumulation of sugars gives rise to the clinical features associated with this disorder. Schindler disease is an autosomal recessive disorder, meaning that one must inherit an abnormal allele from both parents in order to have the disease.

Binswanger's disease, also known as subcortical leukoencephalopathy, is a form of small vessel vascular dementia caused by damage to the white brain matter. White matter atrophy can be caused by many circumstances including chronic hypertension as well as old age. This disease is characterized by loss of memory and intellectual function and by changes in mood. These changes encompass what are known as executive functions of the brain. It usually presents between 54 and 66 years of age, and the first symptoms are usually mental deterioration or stroke.

It was described by Otto Binswanger in 1894, and Alois Alzheimer first used the phrase "Binswanger's disease" in 1902. However, Olszewski is credited with much of the modern-day investigation of this disease which began in 1962.

There is no specific treatment for Farber disease. Corticosteroids may be prescribed to relieve pain. Bone marrow transplants may improve granulomas (small masses of inflamed tissue) on patients with little or no lung or nervous system complications. Older patients may have granulomas surgically reduced or removed.

Life expectancy with Fabry disease for males was 58.2 years, compared with 74.7 years in the general population, and for females 75.4 years compared with 80.0 years in the general population, according to registry data from 2001 to 2008. The most common cause of death was cardiovascular disease, and most of those had received kidney replacements.