The recurrence of DOOR in siblings and the finding of DOOR syndrome in a few families with consanguinity suggest that the condition is an autosomal recessive genetic condition. Mutations in TBC1D24 have been identified in 9 families.

HSAN I constitutes a clinically and genetically heterogeneous group of diseases of low prevalence. Detailed epidemiological data are currently not available. The frequency of the disease is still reflected by reports of a handful affected families. Although the impressive clinical features of HSAN I are seen by neurologists, general practitioners, orthopedists, and dermatologists, the condition might still be under-recognized particularly for sporadic cases and patients who do not exhibit the characteristic clinical features.

DOOR (deafness, onychdystrophy, osteodystrophy, and mental retardation) syndrome is a genetic disease which is inherited in an autosomal recessive fashion. DOOR syndrome is characterized by mental retardation, sensorineural deafness, abnormal nails and phalanges of the hands and feet, and variable seizures. A similar deafness-onychodystrophy syndrome is transmitted as an autosomal dominant trait and has no mental retardation. Some authors have proposed that it may be the same as Eronen Syndrome, but since both disorders are extremely rare it is hard to make a determination.

Marinesco–Sjögren syndrome (MSS), sometimes spelled Marinescu–Sjögren syndrome, is a rare autosomal recessive disorder.

One family of 68 individuals over 5 generations was studied and the prevalence of disease among the family members suggests that it is indicative of dominant inheritance that is not sexually linked. This is supported by the fact that the disease failed to skip generations even in the absence of intermarriages and that disease incidence was independent of sex. The current findings suggest that the cause of the disease could be narrowed down to one enzymatic defect that is involved in the development of neuroectodermal tissue, however the exact molecular mechanisms are currently unknown. The other symptoms that arise such as bone defects and diabetes may be secondary to this enzymatic defect.

The cause of Primrose syndrome is currently unknown. This condition is extremely rare and seems to spontaneously occur, regardless of family history.

In the case studied by Dalai et al. in 2010, it was found that an abnormally high amount of calcitonin, a hormone secreted by the thyroid gland to stabilize blood calcium levels, was present in the blood serum. This suggests that the thyroid gland is releasing an abnormal amount of calcitonin, resulting in the disruption of calcium level homeostasis. No molecular cause was found, but an expanded microarray analysis of the patient found a 225.5 kb deletion on chromosome 11p between rs12275693 and rs1442927. Whether or not this deletion is related to the syndrome or is a harmless mutation is unknown. The deletion was not present in the patient's mother's DNA sample, but the father's DNA was unavailable.

Behr syndrome is characterized by the association of early-onset optic atrophy with spinocerebellar degeneration resulting in ataxia, pyramidal signs, peripheral neuropathy and developmental delay.

Although it is an autosomal recessive disorder, heterozygotes may still manifest much attenuated symptoms. Autosomal dominant inheritance also being reported in a family. Recently a variant of OPA1 mutation with phenotypic presentation like Behr syndrome is also described. Some reported cases have been found to carry mutations in the OPA1, OPA3 or C12ORF65 genes which are known causes of pure optic atrophy or optic atrophy complicated by movement disorder.

Giant axonal neuropathy is a rare, autosomal recessive neurological disorder that causes disorganization of neurofilaments. Neurofilaments form a structural framework that helps to define the shape and size of neurons and are essential for normal nerve function.

If patients with HSAN I receive appropriate treatment and counseling, the prognosis is good. Early treatment of foot infections may avoid serious complications. Nevertheless, the complications are manageable, thus allowing an acceptable quality of life. The disease progresses slowly and does not influence the life expectancy if signs and symptoms are properly treated.

Onset : Early childhood

Progression: Chronic progressive

Clinical: Cerebellar ataxia plus syndrome / Optic Atrophy Plus Syndrome

Ocular: Optic atrophy, nystagmus, scotoma, and bilateral retrobulbar neuritis.

Other: Mental retardation, myoclonic epilepsy, spasticity, and posterior column sensory loss. Tremor in some cases.

Musculoskeletal

Contractures, lower limbs, Achilles tendon contractures, Hamstring contractures, Adductor longus contractures

Systemic

Hypogonadotrophic hypogonadism.

The exact pathophysiological mechanism of Flynn–Aird syndrome is unknown. However, several theories are in place with regards to the nature of this disease including the presence of a genetically defective enzyme involving a neuroectodermal tissue constituent. This explanation provides evidence for the late onset of the condition, the intricate findings, the varied nature of the disorder, as well as the genetic incidence. In addition, some aspects of the condition may be linked to a suppressing (S) gene due to the fact that only a small amount of stigmata appeared while the defects were still transmitted in the family studied. A suppressing gene down regulates the phenotypic expression of another gene, especially of a mutant gene. Other abnormalities may be due to endocrine system diseases.

Cooks syndrome is a hereditary disorder which is characterized in the hands by bilateral nail hypoplasia on the thumb, index finger, and middle finger, absence of fingernails (anonychia) on the ring finger and little finger, lengthening of the thumbs, and bulbousness of the fingers. In the feet, it is characterized by absence of toenails and absence/hypoplasia of the distal phalanges. In the second study of this disorder, it was found that the intermediate phalanges, proximal phalanges, and metacarpals were unaffected.

The disorder was first described by Cooks "et al." in 1985 after being discovered in two generations of one family. It was proposed that the inheritance of the disorder is autosomal dominant. A second family, this with three affected generations, confirmed that the inheritance of the disorder is autosomal dominant. Although several genetic disorders exist which can cause anonychia and onychodystrophy, such disorders often cause other anomalies such as deafness, mental retardation, and defects of the hair, eyes, and teeth. Cooks syndrome is not known to cause any such anomalies.

In 1999, a pair of siblings was found with brachydactyly type B. Because the disorder primarily affected the nails and distal phalanges, the research group concluded that brachydactyly type B and Cooks syndrome are the same disorder. However, in 2007, a 2-year-old girl was found with symptoms consistent with both brachydactyly type B and Cooks syndrome. It was found that the two syndromes were distinct clinically, radiologically, and genetically.

The common symptoms in all reported cases of primrose syndrome include ossified pinnae, learning disabilities or mental retardation, hearing problems, movement disorders (ataxia, paralysis, and parkinsonism among others (likely due, in part, to calcification of the basal ganglia), a torus palatinus (a neoplasm on the mouth's hard palate), muscle atrophy, and distorted facial features. Other symptoms usually occur, different in each case, but it is unknown whether or not these symptoms are caused by the same disease.

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.

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".

In at least some case, the gene lesion involves a mutation in the "CSB" gene.

It can be associated with "ERCC6".

Cohen syndrome (also known as Pepper syndrome or Cervenka syndrome, named after Michael Cohen, William Pepper and Jaroslav Cervenka, who researched the illness) is a genetic disorder.

Treatment for MSS is symptomatic and supportive including physical and occupational therapy, speech therapy, and special education. Cataracts must be removed when vision is impaired, generally in the first decade of life. Hormone replacement therapy is needed if hypogonadism is present.

X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.

X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. Carrier females who have only one copy of the mutation do not usually express the phenotype, although differences in X chromosome inactivation can lead to varying degrees of clinical expression in carrier females since some cells will express one X allele and some will express the other. The current estimate of sequenced X-linked genes is 499 and the total including vaguely defined traits is 983.

Some scholars have suggested discontinuing the terms dominant and recessive when referring to X-linked inheritance due to the multiple mechanisms that can result in the expression of X-linked traits in females, which include cell autonomous expression, skewed X-inactivation, clonal expansion, and somatic mosaicism.

DeSanctis–Cacchione syndrome is an extremely rare disorder characterized by the skin and eye symptoms of xeroderma pigmentosum (XP) occurring in association with microcephaly, progressive mental retardation, retarded growth and sexual development, deafness, choreoathetosis, ataxia and quadriparesis.

The most common X-linked recessive disorders are:

- Red-green color blindness, a very common trait in humans and frequently used to explain X-linked disorders. Between seven and ten percent of men and 0.49% to 1% of women are affected. Its commonness may be explained by its relatively benign nature. It is also known as daltonism.

- Hemophilia A, a blood clotting disorder caused by a mutation of the Factor VIII gene and leading to a deficiency of Factor VIII. It was once thought to be the "royal disease" found in the descendants of Queen Victoria. This is now known to have been Hemophilia B (see below).

- Hemophilia B, also known as Christmas Disease, a blood clotting disorder caused by a mutation of the Factor IX gene and leading to a deficiency of Factor IX. It is rarer than hemophilia A. As noted above, it was common among the descendants of Queen Victoria.

- Duchenne muscular dystrophy, which is associated with mutations in the dystrophin gene. It is characterized by rapid progression of muscle degeneration, eventually leading to loss of skeletal muscle control, respiratory failure, and death.

- Becker's muscular dystrophy, a milder form of Duchenne, which causes slowly progressive muscle weakness of the legs and pelvis.

- X-linked ichthyosis, a form of ichthyosis caused by a hereditary deficiency of the steroid sulfatase (STS) enzyme. It is fairly rare, affecting one in 2,000 to one in 6,000 males.

- X-linked agammaglobulinemia (XLA), which affects the body's ability to fight infection. XLA patients do not generate mature B cells. B cells are part of the immune system and normally manufacture antibodies (also called immunoglobulins) which defends the body from infections (the humoral response). Patients with untreated XLA are prone to develop serious and even fatal infections.

- Glucose-6-phosphate dehydrogenase deficiency, which causes nonimmune hemolytic anemia in response to a number of causes, most commonly infection or exposure to certain medications, chemicals, or foods. Commonly known as "favism", as it can be triggered by chemicals existing naturally in broad (or fava) beans.

Unfortunately, there is not one specific treatment option that can rid a person of this syndrome. However, there are many routes one can take to make living with this disease a lot easier. For example, there are many treatment programs that doctors can specialize for patients and their needs. Meeting with a doctor is very crucial and these specializations can be very useful. Also, one can seek help from pediatricians, EENT doctors, audiologists, and orthopedists. Brace fittings, hearing aids, and physical therapy can also be pushed by one's doctor, so that a patient can live normally. Additionally, anticonvulsant drugs can be used to stop seizures.

Giant axonal neuropathy results from mutations in the "GAN" gene, which codes for the protein gigaxonin. This alters the shape of the protein, changing how it interacts with other proteins when organizing the structure of the neuron.

Neurons affected by the altered protein accumulate excess neurofilaments in the axon, the long extension from the nerve cell that transmits its signal to other nerve cells and to muscles. These enlarged or 'giant' axons cannot transmit signals properly, and eventually deteriorate, resulting in the range of neurological anomalies associated with the disorder.

This disease is an autosomal recessive disorder, which means the defective gene is located on an autosome, and both parents must have one copy of the defective gene in order to have a child born with the disorder. The parents of a child with an autosomal recessive disorder are carriers, but are usually not affected by the disorder.

Gillespie syndrome, also called aniridia, cerebellar ataxia and mental deficiency. is a rare genetic disorder. The disorder is characterized by partial aniridia (meaning that part of the iris is missing), ataxia (motor and coordination problems), and, in most cases, intellectual disability. It is heterogeneous, inherited in either an autosomal dominant or autosomal recessive manner. Gillespie syndrome was first described by American ophthalmologist Fredrick Gillespie in 1965.

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.