By 1990, 65 patients had been reported in the literature, with no sex or ethnic preference notable. Some individuals present with minimal malformation; rarely patients have died during infancy as a result of severe central nervous system involvement or respiratory complications. Several syndromes are related to the Freeman–Sheldon syndrome spectrum, but more information is required before undertaking such nosological delineation.

The Roussy–Lévy syndrome is not a fatal disease and life expectancy is normal. However, due to progressive muscle wasting patients may need supportive orthopaedic equipment or wheelchair assistance.

A 2006 review stated that RS often leads renal cancer between ages 30-50. Renal cancer kills about 1 in 3 people, but 5-year survival rates improved between 1974-1976 and 1995-2000, from 52% to 64%.

There are little data on prognosis. Rarely, some patients have died in infancy from respiratory failure; otherwise, life expectancy is considered to be normal.

A study by You et al. was only able to evaluate the 47 documented cases that have been made to date. According to this study, intraocular schwannomas are more prevalent in females as compared to males with a ratio of 3:1. Additionally, individuals are more likely to present with intraocular schwannomas at a younger age than with uveal melanomas, the most common intraocular tumor. According to the participants evaluated in this study, the average age of occurrence was 37 years old, however, it is important to note that the age range documented represented individuals 9–76 years old.

Spinal muscular atrophy with lower extremity predominance (SMA-LED) is an extremely rare neuromuscular disorder of infants characterised by severe progressive muscle atrophy which is especially prominent in legs.

The disorder is associated with a genetic mutation in the "DYNC1H1" gene (the gene responsible also for one of the axonal types of Charcot–Marie–Tooth disease) and is inherited in an autosomal dominant manner. As with many genetic disorders, there is no known cure to SMA-LED.

The condition was first described in a multi-generational family by Walter Timme in 1917. Its linkage to the "DYNC1H1" gene was discovered in 2010 by M. B. Harms, et al., who also proposed the current name of the disorder.

Kohlschütter-Tönz syndrome (KTS), also called Amelo-cerebro-hypohidrotic syndrome is a rare inherited syndrome characterized by epilepsy, dementia, intellectual disability, and yellow teeth caused by amelogenesis imperfecta (abnormal formation of tooth enamel). It is a type A ectodermal dysplasia.

It is autosomal recessive and symptoms appear in early childhood. The syndrome was first described in 1974 by Alfried Kohlschütter and colleagues. Only 24 affected individuals are known as of 2012. The disease has not been connected to any other known epileptic syndromes. Some but not all cases are associated with mutations in a gene called ROGDI. Another gene that has been associated with this condition is the SCL13A5 gene Diagnoses of this syndrome have occurred in Switzerland, Sicily, the Northern Israel Druze community as well as some other parts of Western Europe.

The expected future course of the disease depends on the subtype of the disease; the individual's sex, age, and initial symptoms; and the degree of disability the person has. Female sex, relapsing-remitting subtype, optic neuritis or sensory symptoms at onset, few attacks in the initial years and especially early age at onset, are associated with a better course.

The average life expectancy is 30 years from the start of the disease, which is 5 to 10 years less than that of unaffected people. Almost 40% of people with MS reach the seventh decade of life. Nevertheless, two-thirds of the deaths are directly related to the consequences of the disease. Suicide is more common, while infections and other complications are especially dangerous for the more disabled. Although most people lose the ability to walk before death, 90% are capable of independent walking at 10 years from onset, and 75% at 15 years.

Other relatively rare conditions have been reported in association with this disease. It is not yet known if these associations are fortuitous or manifestations of the condition itself.

Cerebral cavernomas and massive, macronodular adrenocortical disease have also been reported in association with this syndrome. A case of cutis verticis gyrata, disseminated collagenoma and Charcot-Marie-Tooth disease in association with a mutation in the fumarate hydratase gene has also been reported. Two cases of ovarian mucinous cystadenoma have also been reported with this mutation.

dHMN V has a pattern of autosomal dominance, meaning that only one copy of the gene is needed for the development of the disease. However, there is incomplete penetrance of this disorder, meaning that some individuals with the disease-causing mutations will not display any symptoms. Mutations on chromosome 7 have been linked to this disease. It is allelic (i.e., caused by mutations on the same gene) with Charcot–Marie–Tooth disease and with Silver’s Syndrome, a disorder also characterized by small muscle atrophy in the hands.

Another rare form of dHMN V is associated with a splicing mutation in REEP-1, a gene often associated with hereditary spastic neuroplegia.

Roussy–Lévy syndrome, also known as Roussy–Lévy hereditary areflexic dystasia, is a rare genetic disorder of humans that results in progressive muscle wasting. It is caused by mutations in the genes that code for proteins necessary for the functioning of the myelin sheath of the neurons, affecting the conductance of nerve signals and resulting in loss of muscles' ability to move.

The condition affects people from infants through adults and is inherited in an autosomal dominant manner. Currently, no cure is known for the disorder.

The severity of symptoms vary widely even for the same type of CMT. There have been cases of monozygotic twins with varying levels of disease severity, showing that identical genotypes are associated with different levels of severity (see penetrance). Some patients are able to live a normal life and are almost or entirely asymptomatic. A 2007 review stated that "Life expectancy is not known to be altered in the majority of cases".

Diagnosis occurs based on the two most common features of this syndrome: epilepsy and symmetrical enamel hypoplasia also known as Amelogenesis Imperfecta. Because the tooth discoloration caused by amelogensis imperfecta is often thought to be caused by environmental factors or other diseases, diagnosis of this syndrome is sometimes overlooked. The onset of symptoms can occur when the patient is between one month and four years old, contributing to the misconception that tooth discoloration is due to the environment.

Distal hereditary motor neuropathy type V (dHMN V) is a particular type of neuropathic disorder. In general, distal hereditary motor neuropathies affect the axons of distal motor neurons and are characterized by progressive weakness and atrophy of muscles of the extremities. It is common for them to be called "spinal forms of Charcot-Marie-Tooth disease (CMT)", because the diseases are closely related in symptoms and genetic cause. The diagnostic difference in these diseases is the presence of sensory loss in the extremities. There are seven classifications of dHMNs, each defined by patterns of inheritance, age of onset, severity, and muscle groups involved. Type V (sometimes notated as Type 5) is a disorder characterized by autosomal dominance, weakness of the upper limbs that is progressive and symmetrical, and atrophy of the small muscles of the hands.

Currently, purine replacement via S-adenosylmethionine (SAM) supplementation in people with Arts syndrome appears to improve their condition. This suggests that SAM supplementation can alleviate symptoms of PRPS1 deficient patients by replacing purine nucleotides and open new avenues of therapeutic intervention. Other non-clinical treatment options include educational programs tailored to their individual needs. Sensorineural hearing loss has been treated with cochlear implantation with good results. Ataxia and visual impairment from optic atrophy are treated in a routine manner. Routine immunizations against common childhood infections and annual influenza immunization can also help prevent any secondary infections from occurring.

Regular neuropsychological, audiologic, and ophthalmologic examinations are also recommended.

Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the disease-causing mutation in the family is known.

MS is the most common autoimmune disorder of the central nervous system. As of 2010, the number of people with MS was 2–2.5 million (approximately 30 per 100,000) globally, with rates varying widely in different regions. It is estimated to have resulted in 18,000 deaths that year. In Africa rates are less than 0.5 per 100,000, while they are 2.8 per 100,000 in South East Asia, 8.3 per 100,000 in the Americas, and 80 per 100,000 in Europe. Rates surpass 200 per 100,000 in certain populations of Northern European descent. The number of new cases that develop per year is about 2.5 per 100,000.

Rates of MS appear to be increasing; this, however, may be explained simply by better diagnosis. Studies on populational and geographical patterns have been common and have led to a number of theories about the cause.

MS usually appears in adults in their late twenties or early thirties but it can rarely start in childhood and after 50 years of age. The primary progressive subtype is more common in people in their fifties. Similar to many autoimmune disorders, the disease is more common in women, and the trend may be increasing. As of 2008, globally it is about two times more common in women than in men. In children, it is even more common in females than males, while in people over fifty, it affects males and females almost equally.

Without treatment, persons with MEN2B die prematurely. Details are lacking, owing to the absence of formal studies, but it is generally assumed that death in the 30s is typical unless prophylactic thyroidectomy and surveillance for pheochromocytoma are performed (see below). The range is quite variable, however: death early in childhood can occur, and it is noteworthy that a few untreated persons have been diagnosed in their 50s. Recently, a larger experience with the disease "suggests that the prognosis in an individual patient may be better than previously considered."

Thyroidectomy is the mainstay of treatment, and should be performed without delay as soon as a diagnosis of MEN2B is made, even if no malignancy is detectable in the thyroid. Without thyroidectomy, almost all patients with MEN2B develop medullary thyroid cancer, in a more aggressive form than MEN 2A. The ideal age for surgery is 4 years old or younger, since cancer may metastasize before age 10.

Pheochromocytoma - a hormone secreting tumor of the adrenal glands - is also present in 50% of cases. Affected individuals are encouraged to get yearly screenings for thyroid and adrenal cancer.

Because prophylactic thyroidectomy improves survival, blood relatives of a person with MEN2B should be evaluated for MEN2B, even if lacking the typical signs and symptoms of the disorder.The mucosal neuromas of this syndrome are asymptomatic and self-limiting, and present no problem requiring treatment. They may, however, be surgically removed for aesthetic purposes or if they are being constantly traumatized.

Dejerine–Sottas neuropathy is caused by a genetic defect either in the proteins found in axons or the proteins found in myelin. Specifically, it has been associated with mutations in "MPZ", "PMP22", "PRX", and "EGR2" genes. The disorder is inherited in an autosomal dominant or autosomal recessive manner.

This syndrome has two forms, A and B, referred to as Morquio A and Morquio B syndrome or MPA IVA and MPS IVB. The two forms are distinguished by the gene product involved; A involves a malfunction in the GALNS gene product (galactosamine-6 sulfatase), while B involves a malfunction of the GLB1 gene product (beta-galactosidase).

Hereditary motor and sensory neuropathies are relatively common and are often inherited with other neuromuscular conditions, and these co morbidities cause an accelerated progression of the disease.

Most forms HMSN affects males earlier and more severely than females, but others show no predilection to either sex. HMSN affects all ethnic groups. With the most common forms having no racial prediliections, but other recessively inherited forms tend to impact specific ethnic groups. Onset of HMSN in most common in early childhood, with clinical effects occurring before the age of 10, but some symptoms are lifelong and progress slowly. Therefore, these symptoms do not appear until later in life.

CMT is a result of genetic mutations in a number of genes. Based on the affected gene, CMT can be categorized into types and subtypes.

Arts syndrome is a rare metabolic disorder that causes serious neurological problems in males due to a malfunction of the PRPP synthetase 1 enzyme. Arts Syndrome is part of a spectrum of PRPS-1 related disorders with reduced activity of the enzyme that includes Charcot–Marie–Tooth disease and X-linked non-syndromic sensorineural deafness.

Dejerine–Sottas disease, also known as Dejerine–Sottas syndrome, Dejerine–Sottas neuropathy, progressive hypertrophic interstitial polyneuropathy of childhood and onion bulb neuropathy (and, "hereditary motor and sensory polyneuropathy type III" and "Charcot–Marie–Tooth disease type 3"), is a hereditary neurological disorder characterised by damage to the peripheral nerves and resulting progressive muscle wasting. The condition is caused by mutations in a various genes and currently has no known cure.

The disorder is named for Joseph Jules Dejerine and Jules Sottas, French neurologists who first described it.

The treatment for Morquio syndrome consists of prenatal identification and of enzyme replacement therapy. On 12 February 2014, the US Food and Drug Administration approved the drug elosulfase alfa (Vimizim) for treating the disease.

Non-steroidal anti-inflammatory drugs (NSAIDs) can give significant relief of the symptoms. Treatment of lung cancer or other causes of hypertrophic osteoarthropathy results in regression of symptoms for some patients.