The reported incidence of constriction ring syndrome varies from 1/1200 and 1/15000 live births. The prevalence is equally in male and female.

Fetomaternal factors like prematurity, maternal illnes, low birth weight and maternal drug exposure are predisposing factors for the constriction ring syndrome.

No positive relationship between CRS and genetic inheritance has been reported.

Malformations of the upper extremities can occur In the third to seventh embryonic week. In some cases the TPT is hereditary. In these cases, there is a mutation on chromosome 7q36. If the TPT is hereditary, it is mostly inherited as an autosomal dominant trait, non-opposable and bilateral. The sporadic cases are mostly opposable and unilateral.

Triphalangeal thumb can occur in syndromes but it can also be isolated. The triphalangeal thumb can appear in combination with other malformations or syndromes.

Syndromes include:

- Holt-Oram syndrome

- Aase syndrome

- Blackfan-Diamond syndrome

- Townes-Brocks syndrome

Malformations include:

- Radial polydactyly

- Syndactyly

- Claw-like hand or foot

The exact cause of the condition is unknown. In some cases, close family members may share this condition. In other cases, no other related persons have this condition. The scientific name for the condition is syndactyly, although this term covers both webbed fingers and webbed toes. Syndactyly occurs when apoptosis or programmed cell death during gestation is absent or incomplete. Webbed toes occur most commonly in the following circumstances:

- Syndactyly or Familial Syndactyly

- Down syndrome

It is also associated with a number of rare conditions, notably:

- Aarskog–Scott syndrome

- Acrocallosal syndrome

- Apert's syndrome

- Bardet-Biedl syndrome

- Carpenter syndrome

- Cornelia de Lange syndrome

- Edwards syndrome

- Jackson–Weiss syndrome

- Fetal hydantoin syndrome

- Miller syndrome

- Pfeiffer syndrome

- Smith-Lemli-Opitz syndrome

- Timothy syndrome

- Ectodermal Dysplasia

- Klippel-Feil Syndrome

Minor degrees of curvature are common. Reports of incidence vary between 1% and 19.5%.

Hand-foot-genital syndrome is inherited in an autosomal dominant manner. The proportion of cases caused by de novo mutations is unknown because of the small number of individuals described. If a parent of the proband is affected, the risk to the siblings is 50%. When the parents are clinically unaffected, the risk to the sibs of a proband appears to be low. Each child of an individual with HFGS has a 50% chance of inheriting the mutation. Prenatal testing may be available through laboratories offering custom prenatal testing for families in which the disease-causing mutation has been identified in an affected family member.

Webbed toes in humans are a purely cosmetic condition. This condition does not impair the ability to perform any activity, including walking, running, or swimming. Depending on the severity and structure of the webbing, there can be some minor consequences.

People with more severe webbed toes may have a slight disadvantage for activities that benefit from prehensile toes, due to the toes being unable to split or move laterally. Although not scientifically proven, some believe that this condition can possibly allow for a slight advantage, specifically, in athletics. Considering your big toe is a main source for balance, having your second and third toe webbed could virtually be seen as having two big toes. Thus, allowing for better balance in athletics such as running or dance.

Psychological stress may arise from the fear of negative reactions to this condition from people who do not have webbed toes, particularly in severe cases where the nails are stuck visibly close together. Many people with webbed toes can physically feel the toes touching under the fused skin, which can cause psychological discomfort. This is due to the nerves of each toe fully developing and independent muscles working. In other cases where the toes are partially webbed, the webbing holds the separate tips of the toes against one another and prevents the muscles from spreading the toes apart, causing the toes and sometimes nails to press together.

However a disadvantage would be a difficulty in wearing flip-flops or other such footwear in warm countries. People with webbed toes may be unable to wear Toe socks or Vibram FiveFingers shoes. Difficulty navigating rough terrain barefoot, such as rocks at a beach is also common. In some cases the toes grow at different lengths causing the toes to buckle or bend and many people with severe webbed toes experience cramping in these toes due to the muscles and ligaments being strained.

Omphalocele has been described in two patients with Apert syndrome by Herman T.E. et al. (USA, 2010) and by Ercoli G. et al. (Argentina, 2014). An omphalocele is a birth defect in which an intestine or other abdominal organs are outside of the body of an infant because of a hole in the bellybutton area. However, the association between omphalocele and Apert syndrome is not confirmed yet, so additional studies are necessary.

Clinodactyly is an autosomal dominant trait that has variable expressiveness and incomplete penetrance.

Clinodactyly can be passed through inheritance and presents as either an isolated anomaly or a component manifestation of a genetic syndrome. Many syndromes are associated with clinodactyly, including Down Syndrome, Turner syndrome, Aarskog syndrome, Carpenter syndrome, Seckel syndrome, Cornelia de Lange syndrome, orofaciodigital syndrome 1, 13q deletion syndrome, XXYY syndrome and Silver–Russell syndrome.

When identified prenatally, for example during obstetric ultrasonography, it may be an indication for intrauterine sampling for fetal chromosome analysis as it is statistically correlated with increased risk of chromosome aberration in the fetus.

Type VII of radial polydactyly is associated with several syndromes:

Holt–Oram syndrome, Fanconi anemia (aplastic anemia by the age of 6), Townes–Brocks syndrome, and Greig cephalopolysyndactyly (also known to occur with ulnar polydactyly).

The syndromes associated with central polydactyly are:

Bardet–Biedl syndrome,

Meckel syndrome,

Pallister–Hall syndrome,

Legius syndrome,

Holt–Oram syndrome,

Also, central polydactyly can be associated with syndactyly and cleft hand.

Other syndromes including polydactyly include acrocallosal syndrome, basal cell nevus syndrome, Biemond syndrome, ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome, mirror hand deformity, Mohr syndrome, oral-facial-digital syndrome, Rubinstein-Taybi syndrome, short rib polydactyly, and VATER association.

It can also occur with a triphalangeal thumb.

Surgery is needed to prevent the closing of the coronal sutures from damaging brain development. In particular, surgeries for the LeFort III or monobloc midface distraction osteogenesis which detaches the midface or the entire upper face, respectively, from the rest of the skull, are performed in order to reposition them in the correct plane. These surgeries are performed by both plastic and oral and maxillofacial (OMS) surgeons, often in collaboration.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

Diagnosis is based on physical examination including radiographs of the hands and feet and imaging studies of the kidneys, bladder, and female reproductive tract. HOXA13 is the only gene known to be associated with HFGS. Approximately 60% of mutations are polyalanine expansions. Molecular genetic testing is clinically available.

There is still some discussion on whether FND is sporadic or genetic. The majority of FND cases are sporadic. Yet, some studies describe families with multiple members with FND. Gene mutations are likely to play an important role in the cause. Unfortunately, the genetic cause for most types of FND remains undetermined.

Craniofrontonasal dysplasia is a very rare genetic condition. As such there is little information and no consensus in the published literature regarding the epidemiological statistics.

The incidence values that were reported ranged from 1:100,000 to 1:120,000.

Oligodactyly (from the Ancient Greek "oligos" meaning "few" and δάκτυλος "daktylos" meaning "finger") is the presence of fewer than five fingers or toes on a hand or foot.

It is quite often incorrectly called "hypodactyly", but the Greek prefixes and are used for scales (e.g. in hypoglycaemia and hypercholesterolemia). This as opposed to or scales, where and should be used (e.g. in oligarchy and polygamy). Oligodactyly is therefore the opposite of polydactyly. Very rare, this medical condition usually has a genetic or familial cause.

Oligodactyly is sometimes a sign or symptom of several syndromes including Poland syndrome and Weyer Ulnar Ray Syndrome. It is a type of Dysmelia.

Ectrodactyly is an extreme instance of oligodactyly, involving the absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly of the two) with similar abnormalities of the feet.

People with oligodactyly often have full use of the remaining digits and adapt well to their condition. They are not greatly hindered in their daily activities, if at all. Even those with the most extreme forms are known to engage in tasks that require fine control, such as writing and bootmaking as well as working as a cab driver.

Vadoma people of Zimbabwe have a high frequency of oligodactyly.

According to the National Human Genome Research Institute, Poland syndrome affects males three times as often as females and affects the right side of the body twice as often as the left. The incidence is estimated to range from one in 7,000 to one in 100,000 live births.

The cause of frontorhiny is a mutation in the ALX3 gene. ALX3 is essential for normal facial development. Different mutations can occur in the ALX3 gene, but they all lead to the same effect: severe or complete loss of protein functionality. The ALX3 mutation never occurs in a person without frontorhiny.

Surgical correction is recommended when a constriction ring results in a limb contour deformity, with or without lymphedema.

The cause of Poland syndrome is unknown. However, an interruption of the embryonic blood supply to the arteries that lie under the collarbone (subclavian arteries) at about the 46th day of embryonic development is the prevailing theory.

The subclavian arteries normally supply blood to embryonic tissues that give rise to the chest wall and hand. Variations in the site and extent of the disruption may explain the range of signs and symptoms that occur in Poland syndrome. Abnormality of an embryonic structure called the apical ectodermal ridge, which helps direct early limb development, may also be involved in this disorder.

In the above brachydactyly syndromes, short digits are the most prominent of the anomalies, but in many other syndromes (Down syndrome, Rubinstein-Taybi syndrome, etc.), brachydactyly is a minor feature compared to the other anomalies or problems comprising the syndrome.

Currently there are only around 26 people in the world that are known to have this rare condition. Inheritance is thought to be X-linked recessive.

Five types of syndactyly have been identified in humans. The corresponding loci associated with these types and their common phenotypical expression are as follows:

- "type I": 2q34-q36; webbing occurs between middle and ring fingers and/or second and third toes.

- "type II": 2q31; also involves long and ring fingers, but has a sixth finger merged in between.

- "type III": 6q21-q23; small finger is merged into the ring finger.

- "type IV": 7q36; involves all fingers and/or toes.

- "type V": 2q31-q32; similar to type I, but the metacarpals and metatarsals may also be fused.

The most common problem with syndactyly correction is creeping of the skin towards the fingertip over time. This is likely due to tension at the site of the repair between the digits. Additional surgery may be required to correct this. One critique of using skin grafts is that the grafts darken in the years after surgery and become more noticeable. Also, if the skin grafts are harvested from the groin area, the skin may grow hair. Finally, the fingers may deviate after surgery. This is most commonly seen in complex syndactyly (when there has been a bony joining of the fingers).