Dysmelia can be caused by

- inheritance of abnormal genes, e.g. polydactyly, ectrodactyly or brachydactyly, symptoms of deformed limbs then often occur in combination with other symptoms (syndromes)

- external causes during pregnancy (thus not inherited), e.g. via amniotic band syndrome

- teratogenic drugs (e.g. thalidomide, which causes phocomelia) or environmental chemicals

- ionizing radiation (nuclear weapons, radioiodine, radiation therapy)

- infections

- metabolic imbalance

The overall prognosis is excellent in most cases. Most children with Adams–Oliver syndrome can likely expect to have a normal life span. However, individuals with more severe scalp and cranial defects may experience complications such as hemorrhage and meningitis, leading to long-term disability.

In a newborn boy thought to have Fryns syndrome, Clark and Fenner-Gonzales (1989) found mosaicism for a tandem duplication of 1q24-q31.2. They suggested that the gene for this disorder is located in that region. However, de Jong et al. (1989), Krassikoff and Sekhon (1990), and Dean et al. (1991) found possible Fryns syndrome associated with anomalies of chromosome 15, chromosome 6, chromosome 8(human)and chromosome 22, respectively. Thus, these cases may all represent mimics of the mendelian syndrome and have no significance as to the location of the gene for the recessive disorder.

By array CGH, Slavotinek et al. (2005) screened patients with DIH and additional phenotypic anomalies consistent with Fryns syndrome for cryptic chromosomal aberrations. They identified submicroscopic chromosome deletions in 3 probands who had previously been diagnosed with Fryns syndrome and had normal karyotyping with G-banded chromosome analysis. Two female infants were found to have microdeletions involving 15q26.2 (see 142340), and 1 male infant had a deletion in band 8p23.1 (see 222400).

Usually observed at birth or shortly thereafter in 94% of patients, in other reports, patients did not develop skin lesions until 3 months or even 2 years after birth. Females are typically affected more often than males (64%).

Ectromelia is a congenital condition where long bones are missing or underdeveloped.

Examples include:

- Amelia

- Hemimelia

- Phocomelia

- Sirenomelia

Möbius syndrome results from the underdevelopment of the VI and VII cranial nerves. The VI cranial nerve controls lateral eye movement, and the VII cranial nerve controls facial expression.

The causes of Möbius syndrome are poorly understood. Möbius syndrome is thought to result from a vascular disruption (temporary loss of bloodflow) in the brain during prenatal development. There could be many reasons that a vascular disruption leading to Möbius syndrome might occur. Most cases do not appear to be genetic. However, genetic links have been found in a few families. Some maternal trauma may result in impaired or interrupted blood flow (ischemia) or lack of oxygen (hypoxia) to a developing fetus. Some cases are associated with reciprocal translocation between chromosomes or maternal illness. In the majority of cases of Möbius syndrome in which autosomal dominant inheritance is suspected, sixth and seventh cranial nerve paralysis (palsy) occurs without associated limb abnormalities.

The use of drugs and a traumatic pregnancy may also be linked to the development of Möbius syndrome. The use of the drugs misoprostol or thalidomide by women during pregnancy has been linked to the development of Möbius syndrome in some cases. Misoprostol is used to induce abortions in Brazil and Argentina as well as in the United States. Misoprostol abortions are successful 90% of the time, meaning that 10% of the time the pregnancy continues. Studies show that the use of misoprostal during pregnancy increases the risk of developing Möbius syndrome by a factor of 30. While this is a dramatic increase in risk, the incidence of Möbius syndrome without misoprostal use is estimated at one in 50000 to 100000 births (making the incidence of Möbius syndrome with misoprostol use, less than one in 1000 births). The use of cocaine (which also has vascular effects) has been implicated in Möbius syndrome.

Some researchers have suggested that the underlying problem of this disorder could be congenital hypoplasia or agenesis of the cranial nerve nuclei. Certain symptoms associated with Möbius syndrome may be caused by incomplete development of facial nerves, other cranial nerves, and other parts of the central nervous system.

All cases reported appear to represent sporadic occurrence. There is no specific inheritance pattern. The male-to-female ratio of affected is 1.8:1 and is often diagnosed before the age of 9. The disorder affects the right and left sides of the maxilla almost equally.

The prognosis is favorable in most patients with an isolated cutaneous abnormality. In the majority of cases, both the vivid red marking and the difference in circumference of the extremities regress spontaneously during the first year of life. It is theorized that this may be due to the normal maturation process, with thickening of the epidermis and dermis. Improvements for some patients can continue for up to 10 years, while in other cases, the marbled skin may persist for the patient's lifetime.

One study reported an improvement in lesions in 46% of patients within 3 years. If CMTC persists into adulthood, it can result in complaints due to paresthesia, increased sensitivity to cold and pain, and the formation of ulcers.

Few reports included long-term follow up of CMTC into adolescence and adulthood. While about 50% of patients seem to show definite improvement in the reticular vascular pattern, the exact incidence and cause of persistent cases are unknown.

Between age 5 and 7, most children start losing their primary teeth. Occasionally, some primary teeth are slow to exfoliate (fall out), and the dentist may want to remove a primary tooth early to prevent orthodontic problems. Likewise, premature loss of primary teeth may create orthodontic problems later on. When a tooth is lost prematurely, removable or fixed spacers may be needed to prevent the shifting of teeth. Interceptive orthodontic treatment can be initiated at this stage of development to help with crowding or to help relate the upper and lower jaws. Consistent with a high palate is a narrow arch shape of the upper teeth as they line up in the mouth. This may cause the upper front teeth to flare out and become more prone to fracture if accidentally hit. Interceptive orthodontics has an important role in this situation. Appliances that expand the upper arch tend to bring the front teeth back into a more-normal position. Some appliances can even help allow the front teeth to close to normal in an open-bite situation. The mouth and lips may tend to get dry with the Möbius patient. Lack of a good oral seal (lips together) allows the gingiva (gums) to get dry and may get inflamed and irritated.

AOS is a rare genetic disorder and the annual incidence or overall prevalence of AOS is unknown. Approximately 100 individuals with this disorder have been reported in the medical literature.

The complete absence of an arm or leg in amelia occurs as a result of the limb formation process being either prevented or interrupted very early in the developing embryo: between 24 and 36 days following fertilization. Tetra-amelia syndrome appears to have an autosomal recessive pattern of inheritance - that is, the parents of an individual with tetra-amelia syndrome each carry one copy of the mutated gene, but do not show signs and symptoms of the condition. In a few cases, amelia may be attributed to health complications during the early stages of pregnancy, including infection, failed abortion or complications associated with removal of an IUD after pregnancy, or use of teratogenic drugs, such as thalidomide.

Tetra-amelia syndrome has been reported in only a few families worldwide.

According to a 2011 study by Bermejo-Sanchez, amelia – that is, the lacking of one or more limbs – occurs in roughly 1 out of every 71,000 pregnancies.

In France, Aymé, "et al." (1989) estimated the prevalence of Fryns syndrome to be 0.7 per 10,000 births based on the diagnosis of 6 cases in a series of 112,276 consecutive births (live births and perinatal deaths).

The exact cause of congenital amputation is unknown and can result from a number of causes. However, most cases show that the first three months in a pregnancy are when most birth defects occur because that is when the organs of the fetus are beginning to form. One common cause is amniotic band syndrome, which occurs when the inner fetal membrane (amnion) ruptures without injury to the outer membrane (chorion). Fibrous bands from the ruptured amnion float in the amniotic fluid and can get entangled with the fetus, thus reducing blood supply to the developing limbs to such an extent that the limbs can become strangulated; the tissues die and are absorbed into the amniotic fluid. A baby with congenital amputation can be missing a portion of a limb or the entire limb, which results in the complete absence of a limb beyond a certain point where only a stump is left is known as transverse deficiency or amelia. When a specific part is missing, it is referred to as longitudinal deficiency. Finally, phocomelia occurs when only a mid-portion of a limb is missing; for example when the hands or feet are directly attached to the trunk of the body.

Amnion ruptures can be caused by:

- teratogenic drugs (e.g. thalidomide, which causes phocomelia), or environmental chemicals

- ionizing radiation (atomic weapons, radioiodine, radiation therapy)

- infections

- metabolic imbalance

- trauma

Congenital amputation is the least common reason for amputation, but it is projected that one in 2000 babies are born each year with a missing or deformed limb. During certain periods in history, an increase in congenital amputations has been documented. One example includes the thalidomide tragedy that occurred in the 1960s when pregnant mothers were given a tranquilizer that contained the harmful drug, which produced an increase in children born without limbs. Another example was the 1986 Chernobyl catastrophe in Ukraine, where the radiation exposure caused many children to be born with abnormal or missing limbs .

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.

Studies suggest that prenatal care for mothers during their pregnancies can prevent congenital amputation. Knowing environmental and genetic risks is also important. Heavy exposure to chemicals, smoking, alcohol, poor diet, or engaging in any other teratogenic activities while pregnant can increase the risk of having a child born with a congenital amputation. Folic acid is a multivitamin that has been found to reduce birth defects.

Dysmelia can refer to

- missing (aplasia) limbs: amelia, oligodactyly, congenital amputation e.g. Tibial or Radial aplasia

- malformation of limbs: shortening (micromelia, rhizomelia or mesomelia), ectrodactyly, phocomelia, meromelia, syndactyly, brachydactyly, club foot

- too many limbs: polymelia, polydactyly, polysyndactyly

- others: Tetraamelia, hemimelia, Symbrachydactyly

Adducted thumb syndrome recessive form is a rare disease affecting multiple systems causing malformations of the palate, thumbs, and upper limbs. The name Christian syndrome derives from Joe. C. Christian, the first person to describe the condition. Inheritance is believed to be autosomal recessive, caused by mutation in the CHST14 (carbohydrate sulfotransferase 14) gene.

The gene for Darwin's tubercle was once thought to be inherited in an autosomal dominant pattern with incomplete penetrance, meaning that those who possess the allele (version of a gene) will not necessarily present with the phenotype. However, genetic and family studies have demonstrated that the presence of Darwin's Tubercle may be more likely to be influenced by one's environment or developmental accidents than it is by genetics alone. There is no clear argument for whether the trait has significance in sexual dimorphism studies or age related studies. In some studies, there is clear data that Darwin's tubercle is not associated with sex. In contrast, others indicate that there is a correlation with sexual dimorphism between men and women, where men tend to have the tubercle more than women in some populations. Two studies indicate that older men tend to have greater expression of Darwin's tubercle than do older women.

It is a rare developmental disorder that affects maxilla, also known as the upper jaw in most vertebrates. The disorder is often diagnosed in early childhood. Since its original description as hemimaxillofacial dysplasia by doctors in 1987, less than 40 cases have been reported in the English literature.

Congenital limb deformities are congenital musculoskeletal disorders which primarily affect the upper and lower limbs.

An example is polydactyly.

The diagnosis of tetra-amelia syndrome is established clinically and can be made on routine prenatal ultrasonography. WNT3 is the only gene known to be associated with tetra-amelia syndrome. Molecular genetic testing on a clinical basis can be used to diagnose the incidence of the syndrome. The mutation detection frequency is unknown as only a limited number of families have been studied. Affected infants are often stillborn or die shortly after birth.

The cause of fibular hemimelia is unclear. Purportedly, there have been some incidents of genetic distribution in a family; however, this does not account for all cases. Maternal viral infections, embryonic trauma, teratogenic environmental exposures or vascular dysgenesis (failure of the embryo to form a satisfactory blood supply) between four and seven weeks gestation are considered possible causes.

In an experimental mouse model, change in the expression of a homeobox gene led to similar, but bilateral, fibular defects.

This syndrome is associated with microcephaly, arthrogryposis and cleft palate and various craniofacial, respiratory, neurological and limb abnormalities, including bone and joint defects of the upper limbs, adducted thumbs, camptodactyly and talipes equinovarus or calcaneovalgus. It is characterized by craniosynostosis, and myopathy in association with congenital generalized hypertrichosis.

Patients with the disease are considered intellectually disabled. Most die in childhood. Patients often suffer from respiratory difficulties such as pneumonia, and from seizures due to dysmyelination in the brain's white matter. It has been hypothesized that the Moro reflex (startle reflex in infants) may be a tool in detecting the congenital clapsed thumb early in infancy. The thumb normally extends as a result of this reflex.

Yim–Ebbin syndrome is a congenital disorder characterized by the absence of arms, a cleft lip and palate, hydrocephalus, and an iris coloboma. It was first described by Yim and Ebbin in 1982, and later by Thomas and Donnai in 1994. In 1996, a third case was reported by Froster et al. who suggested that the three cases were related and represented a distinct syndrome. In 2000, a similar case was reported by Pierri et al.

It is also known as "amelia cleft lip palate hydrocephalus iris coloboma".