This condition is very rare, only affecting one in two million people. It is more common in females than in males. There are several hundred cases in the United States, 25 known cases in the United Kingdom, and less than that in Australia and New Zealand.

Most people with the disease need laser repairs to the retina, and about 60 per cent need further surgery.

In those with SS, symptoms typically dramatically improve with low-dose administration of levodopa (L-dopa). L-DOPA exists as a biochemically significant metabolite of the amino acid phenylalanine, as well as a biological precursor of the catecholamine dopamine, a neurotransmitter. (Neurotransmitters are naturally produced molecules that may be sequestered following the propagation of an action potential down a nerve towards the axon terminal, which in turn may cross the synaptic junction between neurons, enabling neurons to communicate in a variety of ways.) Low-dose L-dopa usually results in near-complete or total reversal of all associated symptoms for these patients. In addition, the effectiveness of such therapy is typically long term, without the complications that often occur for those with Parkinson's disease who undergo L-dopa treatment. Thus, most experts indicate that this disorder is most appropriately known as dopa-responsive dystonia (SS).

No data are available on mortality associated with SS, but patients surviving beyond the fifth decade with treatment have been reported. However, in severe, early autosomal recessive forms of the disease, patients have been known to pass away during childhood. Girls seem to be somewhat more commonly affected. The disease less commonly begins during puberty or after age 20, and very rarely, cases in older adults have been reported.

Due to commonly being misdiagnosed, it is common for the disease to remain untreated. When left untreated, patients often need achilles tendon surgery by the age of 21. They will also struggle with walking, an ability that will degrade throughout the day. Power napping can provide temporary relief in untreated patients. It also impairs development into adulthood, reduces balance, and reduces calf muscle development. Socially, it can result in depression, lack of social skills, and inability to find employment.

Wagner's syndrome has for a long time been considered a synonym for Stickler's syndrome. However, since the gene that is responsible for Wagner disease (and Erosive Vitreoretinopathie) is known (2005), the confusion has ended. For Wagner disease is the Versican gene (VCAN) located at 5q14.3 is responsible.

For Stickler there are 4 genes are known to cause this syndrome: COL2A1 (75% of Stickler cases), COL11A1 (also Marshall syndrome), COL11A2 (non-ocular Stickler) and COL9A1 (recessive Stickler).

The gene involved helps regulate how the body makes collagen, a sort of chemical glue that holds tissues together in many parts of the body. This particular collagen gene only becomes active in the jelly-like material that fills the eyeball; in Wagner's disease this "vitreous" jelly grabs too tightly to the already weak retina and pulls it away.

Prevalence is estimated to be 0.005%. The age of onset has been found to be under 15 years in 40% of cases while it is between 10 and 14 years in one third of the cases. Females outnumber males, 4 to 1. Only 3% have attacks after age 52.

Autosomal dominant porencephaly type I is rare and its prevalence and incidence are unknown. It affects males and females equally.

X-linked dystonia parkinsonism is thought to result from a mutation of the TAF1 (TATA-binding protein-associated factor 1) gene at Xq13.1. It has an X-linked, recessive pattern of inheritance. Genetic analysis suggests that the responsible mutation was introduced into the Ilongo ethnic group of the Panay Island over 2000 years ago.

In utero exposure to cocaine and other street drugs can lead to septo-optic dysplasia.

Many other neurological conditions are associated with acanthocytosis but are not considered 'core' acanthocytosis syndromes. The commonest are:

- Pantothenate kinase-associated neurodegeneration, an autosomal recessive condition caused by mutations in "PANK2".

- Huntington's disease-like syndrome type 2, an autosomal dominant condition caused by mutations in "JPH3" that closely resembles Huntington's disease.

- Bassen-Kornzweig disease, or Bassen-Kornzweig Syndrome (see also History).

- Levine-Critchley syndrome (see History).

- Paroxysmal movement disorders associated with GLUT1 mutations.

- Familial acanthocytosis with paroxysmal exertion-induced dyskinesias and epilepsy (FAPED).

- Some cases of mitochondrial disease.

The number cases of PRES that occur each year is not known. It may be somewhat more common in females.

Retinitis pigmentosa is the leading cause of inherited blindness, with approximately 1/4,000 individuals experiencing the non-syndromic form of their disease within their lifetime. It is estimated that 1.5 million people worldwide are currently affected. Early onset RP occurs within the first few years of life and is typically associated with syndromic disease forms, while late onset RP emerges from early to mid-adulthood.

Autosomal dominant and recessive forms of retinitis pigmentosa affect both male and female populations equally; however, the less frequent X-linked form of the disease affects male recipients of the X-linked mutation, while females usually remain unaffected carriers of the RP trait. The X-linked forms of the disease are considered severe, and typically lead to complete blindness during later stages. In rare occasions, a dominant form of the X-linked gene mutation will affect both males and females equally.

Due to the genetic inheritance patterns of RP, many isolate populations exhibit higher disease frequencies or increased prevalence of a specific RP mutation. Pre-existing or emerging mutations that contribute to rod photoreceptor degeneration in retinitis pigmentosa are passed down through familial lines; thus, allowing certain RP cases to be concentrated to specific geographical regions with an ancestral history of the disease. Several hereditary studies have been performed to determine the varying prevalence rates in Maine (USA), Birmingham (England), Switzerland (affects 1/7000), Denmark (affects 1/2500), and Norway. Navajo Indians display an elevated rate of RP inheritance as well, which is estimated as affecting 1 in 1878 individuals. Despite the increased frequency of RP within specific familial lines, the disease is considered non-discriminatory and tends to equally affect all world populations.

X-linked dystonia parkinsonism (XDP), also known as Lubag Syndrome or X-linked Dystonia of Panay, is a rare x-linked progressive movement disorder with high penetrance found almost exclusively in males from the Panay, Philippines. It is characterized by dystonic movements first typically occurring in the 3rd and 4th decade of life. The dystonic movements often either coexist or develop into parkinsonism within 10 years of disease onset.

Many cases resolve within 1–2 weeks of controlling blood pressure and eliminating the inciting factor. However some cases may persist with permanent neurologic impairment in the form of visual changes and seizures among others. Though uncommon, death may occur with progressive swelling of the brain (cerebral edema), compression of the brainstem, increased intracranial pressure, or a bleed in the brain (intracerebral hemorrhage). PRES may recur in about 5-10% of cases; this occurs more commonly in cases precipitated by hypertension as opposed to other factors (medications, etc.).

Treatment for autosomal dominant porencephaly type I is based on the symptoms that an individual is experiencing - for example, treatment of seizures with anticonvulsants. It is particularly important for individuals with this disorder and hypertension to control their blood pressure, as they are at higher risk of stroke. Other stroke prevention treatments include avoiding anticoagulants, smoking, and situations that may lead to head trauma.

Overall, the prognosis for patients with NOMID is not good, though many (80%) live into adulthood, and a few appear to do relatively well. They are at risk for leukemia, infections, and some develop deposits of protein aggregated called amyloid, which can lead to kidney failure and other problems. The neurologic problems are most troubling. The finding that other diseases are related and a better understanding of where the disease comes from may lead to more effective treatments.

Mohr–Tranebjærg syndrome (MTS) is a rare X-liked recessive syndrome also known as deafness–dystonia syndrome and caused by mutation in the TIMM8A gene. It was first described in 1960. The severity of the symptoms may vary, but they progress usually to severe deafness and dystonia and sometimes are accompanied by cortical deterioration of vision and mental deterioration.

The prognosis for individuals with severe LNS is poor. Death is usually due to renal failure or complications from hypotonia, in the first or second decade of life. Less severe forms have better prognoses.

Vestibulocochlear dysfunction progressive familial, known also as familial progressive vestibulocochlear dysfunction is an autosomal dominant disease that results in sensorineural hearing loss and vestibular areflexia. Patients report feelings of vague dissiness, blurred vision, dysequilibrium in the dark, and progressive hearing impairment.

McLeod syndrome is an X-linked recessive disorder caused by mutations in the "XK" gene encoding the Kx blood type antigen, one of the Kell antigens.

Like the other neuroacanthocytosis syndromes, McLeod syndrome causes movement disorder, cognitive impairment and psychiatric symptoms. The particular features of McLeod syndrome are heart problems such as arrhythmia and dilated cardiomyopathy (enlarged heart).

McLeod syndrome is very rare. There are approximately 150 cases of McLeod syndrome worldwide. Because of its X-linked mode of inheritance, it is much more prevalent in males.

In some cases Meige's syndrome can be reversed when it is caused by medication. It has been theorized that it is related to cranio-mandibular orthopedic misalignment, a condition that has been shown to cause a number of other movement disorders (Parkinon's, tourettes, and torticollis). This theory is supported by the fact that the trigeminal nerve is sensory for blink reflex, and becomes hypertonic with craniomandibular dysfunction. Palliative treatments are available, such as botulinum toxin injections.

Rare familial recurrence has been reported, suggesting at least one genetic form (HESX1). In addition to HESX1, mutations in OTX2, SOX2 and PAX6 have been implicated in de Morsier syndrome, but in most cases SOD is a sporadic birth defect of unknown cause and does not recur with subsequent pregnancies.

Miller-Dieker occurs in less than one in 100000 people and can occur in all races.

This is a rare condition with an incidence estimated to be less than 1 in a million live births. About 100 cases have been reported worldwide. The bulk of cases are sporadic but familial forms with autosomal dominant transmission have also been described.

Males with pathogenic "MECP2" mutations usually die within the first 2 years from severe encephalopathy, unless they have an extra X chromosome (often described as Klinefelter syndrome), or have somatic mosaicism.

Male fetuses with the disorder rarely survive to term. Because the disease-causing gene is located on the X chromosome, a female born with an MECP2 mutation on her X chromosome has another X chromosome with an ostensibly normal copy of the same gene, while a male with the mutation on his X chromosome has no other X chromosome, only a Y chromosome; thus, he has no normal gene. Without a normal gene to provide normal proteins in addition to the abnormal proteins caused by a MECP2 mutation, the XY karyotype male fetus is unable to slow the development of the disease, hence the failure of many male fetuses with a MECP2 mutation to survive to term.

Females with a MECP2 mutation, however, have a non-mutant chromosome that provides them enough normal protein to survive longer. Research shows that males with Rett syndrome may result from Klinefelter's syndrome, in which the male has an XXY karyotype. Thus, a non-mutant "MECP2" gene is necessary for a Rett's-affected embryo to survive in most cases, and the embryo, male or female, must have another X chromosome.

There have, however, been several cases of 46,XY karyotype males with a MECP2 mutation (associated with classical Rett syndrome in females) carried to term, who were affected by neonatal encephalopathy and died before 2 years of age. The incidence of Rett syndrome in males is unknown, partly owing to the low survival of male fetuses with the Rett syndrome-associated MECP2 mutations, and partly to differences between signs caused by MECP2 mutations and those caused by Rett's.

Females can live up to 40 years or more. Laboratory studies on Rett syndrome may show abnormalities such as:

- EEG abnormalities from 2 years of age

- atypical brain glycolipids

- elevated CSF levels of "beta"-endorphin and glutamate

- reduction of substance P

- decreased levels of CSF nerve growth factors

A high proportion of deaths are abrupt, but most have no identifiable cause; in some instances death is the result most likely of:

- spontaneous brainstem dysfunction

- cardiac arrest, likely due to long QT syndrome, ventricular tachycardia or other arrhythmias

- seizures

- gastric perforation

The main symptoms involve involuntary blinking and chin thrusting. Some patients may experience excessive tongue protrusion, squinting, light sensitivity, muddled speech, or uncontrollable contraction of the platysma muscle. Some Meige's patients also have "laryngeal dystonia" (spasms of the larynx). Blepharospasm may lead to embarrassment in social situations, and oromandibular dystonia can affect speech, making it difficult to carry on the simplest conversations. This can cause difficulty in both personal and professional contexts, and in some cases may cause patients to withdraw from social situations.

The condition tends to affect women more frequently than men.