The prevalence of Klippel–Feil syndrome is unknown due to the fact that there was no study done to determine the true prevalence.

Although the actual occurrence for the KFS syndrome is unknown, it is estimated to occur 1 in 40,000 to 42,000 newborns worldwide. In addition, females seem to be affected slightly more often than males.

The heterogeneity of the Klippel–Feil syndrome has made it difficult to outline the diagnosis as well as the prognosis classes for this disease. Because of this, it has complicated the exact explanation of the genetic cause of the syndrome.

The prognosis for most individuals with KFS is good if the disorder is treated early on and appropriately. Activities that can injure the neck should be avoided, as it may contribute to further damage. Other diseases associated with the syndrome can be fatal if not treated, or if found too late to be treatable.

Cervicocranial syndrome (or craniocervical syndrome) is a combination of symptoms that are believed to be caused by an abnormality in the neck. Symptoms often include vertigo, chronic headache, tinnitus, facial pain, ear pain, dysphagia and pain at the carotid artery. It is usually caused by spondylosis.

Benign symmetric lipomatosis is a skin condition characterized by extensive symmetric fat deposits in the head, neck, and shoulder girdle area. The German surgeon Otto Wilhelm Madelung was the first to give a detailed description of the disorder. This condition is very rare, with an estimated incidence rate of 1 in 25,000, and affects males up to 30 times more frequently than females.

The cause of the disease remains unknown, but its incidence strongly correlates with alcohol abuse; abstinence from alcohol prevents disease progression. Defects in the adrenergic-stimulated lipolysis and accumulation of embryological brown fat have also been reported. Cosmetic disfigurement due to the fat deposition in the cervicothoracic region results in a "pseudoathletic appearance", resembling the Italian statue "Warrior of Capestrano" and carvings of Queen of Punt (Egypt). Traditionally the treatment is mainly surgical, consisting of the removal of the lipomas, although recent study has proposed liposuction and phosphatidylcholine injection as possible alternatives.

The injury is immediately fatal in 70% of cases, with an additional 15% surviving to the emergency room, but perishing during their hospital stay. A basion-dental interval of 16mm or greater is associated with mortality. In those with neurologic deficits, survival is unlikely.

The Jefferson fracture can be associated with this injury, with the C1 ring, or atlas, being fractured in several places, allowing the spine to shift forward relative to the skull base. The Hangman's fracture which is a fracture of the C2 vertebral body or dens of the cervical spine upon which the skull base sits to allow the head to rotate, can also be associated with atlanto-occipital dislocation. Despite its eponym, the fracture is not usually associated with a hanging mechanism of injury.

Campomelic dysplasia has a reported incidence of 0.05-0.09 per 10000 live births.

In nearly 95% of the cases, death occurs in the neonatal period due to respiratory distress, generally related to small chest size or insufficient development of the trachea and other upper airway structures.

Among survivors of CMD, the skeletal malformations change over time to include worsening scoliosis or kyphosis resulting in decreased trunk size relative to the limb length. Neurological damage is also often seen including mental retardation and deafness. Even among survivors of the prenatal period, CMD patients have shortened life spans due to lifelong respiratory issues. Those patients with ambiguous genitalia or sex reversal at birth, of course, maintain that state, and are either sterile or have reduced fertility.

Cranioschisis (Greek: "κρανιον - kranion" "skull", and "schisis - σχίσις" - "split") is a developmental birth defect involving the skull. In this disease, the cranium fails to close completely (especially at the occipital region). Thus, the brain is exposed to the amnios, and eventually degenerates, causing anencephaly.

One proposed cause of pilonidal cysts is ingrown hair. Excessive sitting is thought to predispose people to the condition, as sitting increases pressure on the coccygeal region. Trauma is not believed to cause a pilonidal cyst; however, such an event may result in inflammation of an existing cyst. However, there are cases where this can occur months after a localized injury to the area. Some researchers have proposed that pilonidal cysts may be the result of a congenital pilonidal dimple. Excessive sweating can also contribute to the cause of a pilonidal cyst. Moisture can fill a stretched hair follicle, which helps create a low-oxygen environment that promotes the growth of anaerobic bacteria, often found in pilonidal cysts. The presence of bacteria and low oxygen levels hamper wound healing and exacerbate a forming pilonidal cyst.

Bowen–Conradi syndrome (BCS or BWCNS) is a disease in humans that can affect children. The disease is due to an autosomal recessive abnormality of the "EMG1" gene, which plays a role in small ribosomal subunit (SSU) assembly. The preponderance of diagnoses has been in North American Hutterite children, but BWCNS can affect other population groups.

BWCNS is a ribosomopathy. A D86G mutation of "EMG1" destroys an EcoRV restriction endonuclease site in the most highly conserved region of the protein.

Skeletal dysmorphology is seen and severe prenatal and postnatal growth failure usually leads to death by one year of age.

Spinal disease (also known as a dorsopathy) refers to a condition impairing the backbone. These include various diseases of the back or spine ("dorso-"), such as kyphosis. Dorsalgia refers to those conditions causing back pain.

An example is scoliosis. Some other spinal diseases include Spinal Muscular Atrophy, Ankylosing Spondylitis, Lumbar Spinal Stenosis, Spina Bifida, Spinal tumors, Osteoporosis and Cauda Equina Syndrome.

Foville's syndrome is caused by the blockage of the perforating branches of the basilar artery in the region of the brainstem known as the pons. Most frequently caused by vascular disease or tumors involving the dorsal pons.[3]

Structures affected by the infarct are the PPRF, nuclei of cranial nerves VI and VII, corticospinal tract, medial lemniscus, and the medial longitudinal fasciculus. There's involvement of the fifth to eighth cranial nerves, central sympathetic fibres (Horner syndrome) and horizontal gaze palsy.[3]

The disease is inherited by autosomal dominant transmission with complete penetrance but variable expression. This means that children of an affected parent that carries the gene have a 50% chance of developing the disorder, although the extent to which they are affected is variable.

Bart syndrome is caused by ultrastructural abnormalities in the anchoring fibrils. Genetic linkage of the inheritance of the disease points to the region of chromosome 3 near the collagen, type VII, alpha 1 gene (COL7A1).

There are many recognized spinal diseases, some more common than others. Spinal disease also includes cervical spine diseases, which are diseases in the vertebrae of the neck. A lot of flexibility exists within the cervical spine and because of that, it is common for an individual to damage that area, especially over a long period of time. Some of the common cervical spine diseases include degenerative disc disease, cervical stenosis, and cervical disc herniation. Degenerative disc disease occurs over time when the discs within each vertebra in the neck begin to fall apart and begin to disintegrate. Because each vertebra can cause pain in different areas of the body, the pain from the disease can be sensed in the back, leg, neck area, or even the arms. When the spinal canal begins to lose its gap and gets thinner, it can cause pain in the neck, which can also cause a numb feeling in the arms and hands. Those are symptoms of cervical stenosis disease. The discs between each vertebra have fibers that can begin to deteriorate, and this can occur in cervical disc herniation. This disease is less common in younger people as it is usually a function of aging.

While the cause of FMD remains unclear, current theory suggest that there may be a genetic predisposition as case reports have identified clusters of the disease and prevalence among twins. In fact, according to the Cleveland Clinic approximately 10% of cases appear to be inherited and often coexists with other genetic abnormalities that affect the blood vessels. Approximately 10% of patients with FMD have an affected family member. A study conducted from the patient registry at Michigan Cardiovascular Outcomes Research and Reporting Program (MCORRP) at the University of Michigan Health System reported a high prevalence of a family history of stroke (53.5%), aneurysm (23.5%), and sudden death (19.8%). Even though FMD is a non-atherosclerotic disease family histories of hypertension and hyperlipidemia were also common among those diagnosed with FMD. It is believed that the cause of FMD is not a single identifier such as genetics but has multiple underlying factors. Theories of hormonal influence, mechanical stress from trauma and stress to the artery walls, and also the effect of loss of oxygen supply to the blood vessel wall caused by fibrous lesions. It has been suggested that environmental factors, such as smoking and estrogen, may play role in addition to genetic factors.

Bart syndrome is a genetic disorder characterized by the association of congenital localized absence of skin, epidermolysis bullosa, lesions of the mouth mucosa, and dystrophic nails.

According to a 1984 study conducted in Maryland, Hirschsprung's disease appears in 18.6 per 100,000 live births. In Japan, it occurs at a similar rate of about one in 5,000 births (20 per 100,000). It is more common in male than female (4.32:1) and in white rather than nonwhite. Nine percent of the Hirschsprung cases were also diagnosed as having Down syndrome. Most cases are diagnosed before the patient is 10 years of age.

Campomelic dysplasia (CMD) is a rare genetic disorder characterized by bowing of the long bones and many other skeletal and extraskeletal features.

It is frequently lethal in the neonatal period due to respiratory insufficiency, but the severity of the disease is variable, and some patients survive into adulthood.

The name is derived from the Greek roots "campo" (or "campto"), meaning bent, and "melia", meaning limb.

An unusual aspect of the disease is that up to two-thirds of affected 46,XY genotypic males display a range of Disorders of Sexual Development (DSD) and genital ambiguities or may even develop as normal phenotypic females as in complete 46 XY sex reversal.

An atypical form of the disease with absence of bowed limbs is called, prosaically, acampomelic campomelic dysplasia (ACD) and is found in about 10% of patients, particularly those surviving the neonatal period.

Symptoms of the disease are an acute pain and swelling in the hips and knee joints. Some of the other characteristics of this disease are dwarfism from birth, deformation of the limbs after age seven and death as early as between 25 and 30 years or even younger. Depending on the mobility of the affected patients, the disease has been identified with three severities: in mild to moderate cases, the patient is able to walk with difficulty, in severe cases mobility is very restricted, whereas in acute cases the limbs are bent and badly crippled making the patients crawl.

Pilonidal disease is a type of skin infection which typically occurs between the cheeks of the buttocks and often at the upper end. Symptoms may include pain, swelling, and redness. There may also be drainage of fluid. It rarely results in a fever.

Risk factors include obesity, family history, prolonged sitting, greater amounts of hair, and not enough exercise. The underlying mechanism is believed to involve a mechanical process. The lesions may contains hair and skin debris. Diagnosis is based on symptoms and examination.

If there is infection, treatment is generally by incision and drainage just off the midline. Shaving the area may prevent recurrence. More extensive surgery may be required if the disease recurs. Antibiotics are generally not needed. Without treatment the condition may remain long term.

About 3 per 10,000 people are affected a year. It occurs more often in males than females. Often it occurs in young adulthood. The term means "nest of hair". It was first described in 1833.

A team from the National Institute of Nutrition, Hyderabad conducted research in the affected regions and found out that the disease was confined to a dalit colony. They also found out that the disease was affecting people of all age groups and it was non-contagious and non-infectious. This research was further followed by research conducted over four years (1984–88) by the Indian Council of Medical Research (ICMR). Study groups involving experts from different medical fields were formed and these groups visited the affected places to conduct experiments. They were also helped by the Health Department of Karnataka who also provided a team to assist them. Despite undertaking extensive research, the team could not come into any conclusion on the cause of the disease. The team wound up in 1988 and this was the first phase of their research. The second phase of the research by ICMR was started in the year 2001 under the leadership of S. S. Agarwal of the Sanjay Gandhi Post-graduate centre in Lucknow. Some of the activities in the second phase were to x-ray the patients and also study their family history to see if the disease was related to genetics. The study reported that Handigodu syndrome is a syndrome of familial spondyloepi(meta)physeal dysplasia. It is inherited as an autosomal dominant trait. All the presentations of the varied manifestation of the disease could be explained as being caused by defective development of bones as a result of monogenic disorder.

Keratosis Pharyngis is a medical condition where keratin grows on the surface of the pharynx, that is the part of the throat at the back of the mouth. Keratin is a protein that normally occurs as the main constituent of hair and nails.

It is characterized by the presence of whitish-yellow dots on the pharyngeal wall, tonsils or lingual tonsils.

They are firmly adherent and cannot be wiped off.

The surrounding region does not show any sign or inflammation or any other constitutional signs.

The disease usually shows spontaneous regression.

One patient who was diagnosed with Keratosis Pharyngis had white spots on the base of the tongue and on the pharynx, and hurt a little when swallowing. No treatment was found to help, but the condition went away by itself eventually.

This produces ipsilateral horizontal gaze palsy and facial nerve palsy and contralateral hemiparesis, hemisensory loss, and internuclear ophthalmoplegia.

Common and rare DNA variations in the neuregulin 1 (NRG1) and NRG3 (NRG3) were first shown to be associated with the disease in Chinese patients through a Genome Wide Association Study by the Hong Kong team in 2009 and 2012, respectively Subsequent studies in both Asian and Caucasian patients confirmed the initial findings by the University of Hong Kong. Both rare and common variants in these two genes have been identified in additional Chinese, Thai, Korean, Indonesian and Spanish patients. These two genes are known to play a role in the formation of the enteric nervous system; thus, they are likely to be involved in the pathology of Hirschsprung's disease, at least in some cases.

2q37 monosomy is a rare genetic disorder caused by a deletion of a segment at the end of chromosome 2.