Common relevant features of acrocephalosyndactyly are a high-arched palate, pseudomandibular prognathism (appearing as mandibular prognathism), a narrow palate, and crowding of the teeth.

All acrocephalosyndactyly syndromes show some level of limb anomalies, so it can be hard to tell them apart. However, the typical hand deformities in patients with Apert Syndrome distinguish it from the other syndromes.

The hands in patients with Apert syndrome always show four common features:

1. a short thumb with radial deviation

2. complex syndactyly of the index, long and ring finger

3. symbrachyphalangism

4. simple syndactyly of the fourth webspace

The deformity of the space between the index finger and the thumb may be variable. Based on this first webspace, we can differentiate three different types of handdeformation:

- Type I: Also called a "spade hand". The most common and least severe type of deformation. The thumb shows radial deviation and clinodactyly, but is separated from the index finger. The index, long and ring finger are fused together in the distal interphalangeal joints and form a flat palm. During the embryonic stage, the fusion has no effect on the longitudinal growth of these fingers, so they have a normal length. In the fourth webspace, we always see a simple syndactyly, either complete or incomplete.

- Type II: Also called a "spoon" or "mitten" hand. This is a more serious anomaly since the thumb is fused to the index finger by simple complete or incomplete syndactyly. Only the distal phalanx of the thumb is not joined in the osseous union with the index finger and has a separate nail. Because the fusion of the digits is at the level of the distal interphalangeal joints, a concave palm is formed. Most of the time, we see complete syndactyly of the fourth webspace.

- Type III: Also called the "hoof" or "rosebud" hand. This is the most uncommon but also most severe form of hand deformity in Apert syndrome. There is a solid osseous or cartilaginous fusion of all digits with one long, conjoined nail. The thumb is turned inwards and it is often impossible to tell the fingers apart. Usually proper imaging of the hand is very difficult, due to overlap of bones, but physical examination alone is not enough to measure the severity of deformation

The clinical features of this condition include

- Flattened facial features

- Flexion contractures of the interphalangeal joints of hand and foot.

- Limited motion of multiple joints

- Short broad metacarpals, metatarsals and phalanges

Thickening of the skin may occur in a fashion similar to that occurs in scleroderma. The thumbs may be angled in a lateral direction (valgus deformity). The knees may be angled backwards (genu recurvatum). Abnormalities of the upper spinal cord may also occur.

The most common symptoms of Nicolaides–Baraitser syndrome are mild to severe developmental delays with absent or limited speech, seizures, short stature, sparse hair, typical facial characteristics, brachydactyly, and prominent finger joints and broad distal phalanges.

Many of the characteristic facial features (among other) of Jackson–Weiss syndrome result from the premature fusion of the skull bones. The following are some of the more common, such as:

- Preaxial foot polydactyl

- Tarsal synostosis

- Frontal bossing

- Proptosis

Syndactyly can be simple or complex.

- In simple syndactyly, adjacent fingers or toes are joined by soft tissue.

- In complex syndactyly, the bones of adjacent digits are fused. The kangaroo exhibits complex syndactyly.

Syndactyly can be complete or incomplete.

- In complete syndactyly, the skin is joined all the way to the tip of the involved digits.

- In incomplete syndactyly, the skin is only joined part of the distance to the tip of the involved digits.

Complex syndactyly occurs as part of a syndrome (such as Apert syndrome) and typically involves more digits than simple syndactyly.

Fenestrated syndactyly means the skin is joined for most of the digit but in a proximal area there is gap in the syndactyly with normal skin. This type of syndactyly is found in amniotic band syndrome.

Simple syndactyly can be full or partial, and is present at birth (congenital). In early human fetal development, webbing (syndactyly) of the toes and fingers is normal. At about 6 weeks of gestation, apoptosis takes place due to a protein named sonic hedgehog, also known as SHH, which dissolves the tissue between the fingers and toes, and the webbing disappears. In some fetuses, this process does not occur completely between all fingers or toes and some residual webbing remains.

Mild prenatal growth retardation

Moderate postnatal growth retardation

Mild to severe developmental delay

Severely impaired speech

Seizures

Microcephaly

Sparse hair

Progressive skin wrinkling

Thick, anteverted alae nasi

Long and broad philtrum

Large mouth

Thin upper and thick lower vermilion

Progressive prominence of distal phalanges

Progressive prominence of inter-phalangeal joints

Short metacarpals–metatarsals

Jackson–Weiss syndrome (JWS) is a genetic disorder characterized by foot abnormalities and the premature fusion of certain bones of the skull (craniosynostosis), which prevents further growth of the skull and affects the shape of the head and face. This genetic disorder can also sometimes cause intellectual disability and crossed eyes as well, it was characterized in 1976.

Clefts in this variant are slightly more severe than the ones seen in simple macrostomia. It also does not have bone deformities, but it does include minor soft tissue deformities. The defining feature is muscle diastasis which is separation of the masseter. This phenotype can also be partially corrected with surgery.

Numerous associated abnormalities of other organ systems may be present. This heterogeneity requires comprehensive evaluation of all patients and treatment regimes that can vary from modification of activities to extensive spinal surgeries. Furthermore, it is unclear whether Klippel–Feil syndrome is a unique disease, or if it is one part of a spectrum of congenital spinal deformities. Klippel–Feil syndrome is usually diagnosed after birth.

The most common sign of the disorder is restricted mobility of the neck and upper spine. A short neck and low hairline at the back of the head may occur in some patients.

Associated abnormalities may include:

- scoliosis (side-to-side curvature of the spine), which is abnormal curving of the spine. The spine sometimes appears as a "C" or an "S"

- spina bifida, when the spinal canal and the back bone do not close completely during birth

- anomalies of the kidneys and the ribs

- cleft palate (hole in the roof of the mouth)

- dental problems (late dentition, high-risk of caries, oligo- and hypodontia)

- respiratory problems

- heart malformations

- short stature

- Duane syndrome

- Approximately 35% of patients with Klippel–Feil syndrome will also have a congenital elevation of the scapula known as Sprengel's deformity

The disorder also may be associated with abnormalities of the head and face, skeleton, sex organs, muscles, brain and spinal cord, arms, legs, fingers and heart defects. These heart defects often lead to a shortened life expectancy, the average being 35–45 years of age among males and 40–50 among females. This condition is similar to the heart failure seen in gigantism.

In 2011, a study identifying the occurrence of symptoms of 100 patients was published.

This version of macrostomia is less severe because it does not affect the facial muscles and is not associated with any soft tissue or bone deformities. A small cleft(s) extends from the mouth and can be repaired surgically.

Syndactyly (from Greek συν- meaning "together" and δακτυλος meaning "finger") is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans.

In humans, a single transverse palmar crease is a single crease that extends across the palm of the hand, formed by the fusion of the two palmar creases (known in palmistry as the "heart line" and the "head line") and is found in people with Down Syndrome. It is also found in 1.5% of the general population in at least one hand.

Because it resembles the usual condition of non-human simians, it is also known as a simian crease or simian line, although these terms have widely fallen out of favor due to their pejorative connotation.

Gerodermia osteodysplastica is characterized by symptoms and features which affect the connective tissues, skin and skeletal system.

These are: wrinkly, loose skin over the face, abdomen, and extremites (hands, feet) on the dorsal sides usually worsened by chronic joint laxity and hyperextensibility; fragmented elastic fibers of the skin that are reduced in number, with disorientation of collagen fibers; osteopenia and osteoporosis, with associated fractures; malar hypoplasia (underdeveloped cheek bone), maxillary hypoplasia (underdeveloped upper jaw), mandibular prognathism (protrusion of the lower jaw and chin), bowed long bones, platyspondyly (flattened spine) related to vertebral collapse; kyphoscoliosis (scoliosis with kyphosis, or "hunch back"), metaphyseal peg (an unusual outgrowth of metaphyseal tissue which protrudes into the epiphyseal region of the bone, near the knee); and the overall physical effects and facial appearance of dwarfism with premature aging.

Other features and findings include: intrauterine growth retardation, congenital hip dislocations, winged scapulae (shoulder blades), pes planus (fallen arches), pseudoepiphyses of the second metacarpals (upper bone of the fingers), hypotelorism (close-set eyes), malformed ears,

developmental delay,

failure to thrive and abnormal electroencephalograph (EEG) readings.

Dental and orthodontal abnormalities in addition to maxillary hypoplasia and mandibular prognathism have also been observed in gerodermia osteodysplastica. Including malocclusion of the dental arches (the maxilla and mandible), radiological findings in some cases have indicated significant overgrowth of the mandibular premolar and molar roots;

hypercementosis (overproduction of cementum) of the molars and maxillary incisors; enlarged, funnel-shaped mandibular lingula (spiny structures on the ramus of the mandible); and a radiolucent effect on portions of many teeth, increasing their transparency to x-rays.

Singleton Merten Syndrome is an autosomal dominate genetic disorder with variable expression with an onset of symptoms during childhood.

Many of the characteristic facial features result from the premature fusion of the skull bones (craniosynostosis). The head is unable to grow normally, which leads to a high prominent forehead (turribrachycephaly), and eyes that appear to bulge (proptosis) and are wide-set (hypertelorism). In addition, there is an underdeveloped upper jaw (maxillary hypoplasia). About 50 percent of children with Pfeiffer syndrome have hearing loss, and dental problems are also common.

In people with Pfeiffer syndrome, the thumbs and first (big) toes are wide and bend away from the other digits (pollex varus and hallux varus). Unusually short fingers and toes (brachydactyly) are also common, and there may be some webbing or fusion between the digits (syndactyly).

Leri's pleonosteosis is a rare rheumatic condition. It was first described by the French physician Leri in 1921.

Clinical:

Patients often present with a history of fever of unknown origin, muscular weakness, poor development, abnormal dentition, normal serum calcium, phosphorus, and alkaline phosphatase levels. Associated clinical findings also include glaucoma, photosensitivity, heart block, foot deformities, and chronic psoriasiform skin lesions.

Radiological:

Classic radiologic findings were first described by Edward B. Singleton and David Merten in 1973.

Typical radiographic appearances include skeletal demineralization, expanded shafts of the metacarpals and phalanges with widenend medullary cavities, cardiomegaly, and intramural calcification of the proximal aorta with occasional extension into the aortic or mitral valves.

Other commonly seen radiographic findings include shallow acetabular fossa, subluxation of the femoral head, coxa valga, hypoplastic radial epiphysis, soft tissue calcifications between the radius and ulna, constriction of the proximal radial shaft, acro-osteolysis, and equinovarus foot deformities.

Gerodermia osteodysplastica (GO), also called geroderma osteodysplasticum and Walt Disney dwarfism, is a rare autosomal recessive connective tissue disorder included in the spectrum of cutis laxa syndromes.

Usage of the name "Walt Disney dwarfism" is attributed to the first known case of the disorder, documented in a 1950 journal report, in which the authors described five affected members from a Swiss family as having the physical appearance of dwarves from a Walt Disney film.

The terms "geroderma" or "gerodermia" can be used interchangeably with "osteodysplastica" or "osteodysplasticum", with the term "hereditaria" sometimes appearing at the end.

Klippel–Feil syndrome is a rare disease, initially reported in 1884 by Maurice Klippel and André Feil from France, characterized by the congenital fusion of any two of the seven cervical vertebrae.

The syndrome occurs in a heterogeneous group of patients unified only by the presence of a congenital defect in the formation or segmentation of the cervical spine. Klippel-Feil results in limited movement of the neck. Klippel–Feil syndrome is sometimes identified by shortness of the neck, but not all people with this disorder have a visibly shortened neck. Some people with the syndrome have a very low hairline.

In 1919, in his PhD thesis, André Feil suggested another classification of the syndrome encompassing not only deformation of the cervical spine but also deformation of the lumbar and thoracic spine.

Pfeiffer syndrome is a very rare genetic disorder characterized by the premature fusion of certain bones of the skull which affects the shape of the head and face. In addition, the syndrome includes abnormalities of the hands (such as wide and deviated thumbs) and feet (such as wide and deviated big toes). Pfeiffer syndrome affects about 1 in 100,000 births.

This syndrome consists a number of typical features. These include

- Agenesis of the corpus callosum (80-99% patients)

- Hypopigmentation of the eyes and hair (80-99% patients)

- Cardiomyopathy (80-99% patients)

- Combined immunodeficiency (80-99% patients)

- Muscular hypotonia (80-99% patients)

- Abnormality of retinal pigmentation (80-99% patients)

- Recurrent chest infections (80-99% patients)

- Abnormal EEG (80-99% patients)

- Intellectual disability (80-99% patients)

- Cataracts (75%)

- Seizures (65%)

- Renal abnormalities (15%)

Infections of the gastrointestinal and urinary tracts are common. Swallowing and feeding difficulties early on may result in a failure to thrive. Optic nerve hypoplasia, nystagmus and photophobia may occur. Facial dysmorphism (cleft lip/palate and micrognathia) and syndactyly may be present. Sensorineural hearing loss may also be present.

Death in infancy is not uncommon and is usually due to cardiac complications or severe infections.

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.

Splenogonadal fusion is a rare congenital malformation that results from an abnormal connection between the primitive spleen and gonad during gestation. A portion of the splenic tissue then descends with the gonad. Splenogonadal fusion has been classified into two types: continuous, where there remains a connection between the main spleen and gonad; and discontinuous, where ectopic splenic tissue is attached to the gonad, but there is no connection to the orthotopic spleen. Patients with continuous splenogonadal fusion frequently have additional congenital abnormalities, most commonly cryptorchidism.

The anomaly was first described in 1883 by Bostroem. Since then more than 150 cases of splenogonadal fusion have been documented. The condition is considered benign. A few cases of testicular neoplasm have been reported in association with splenogonadal fusion. The reported cases have occurred in patients with a history of cryptorchidism, which is associated with an elevated risk of neoplasm.

Splenogonadal fusion occurs with a male-to-female ratio of 16:1, and is seen nearly exclusively on the left side. The condition remains a diagnostic challenge, but preoperative consideration of the diagnosis may help avoid unnecessary orchiectomy. On scrotal ultrasound, ectopic splenic tissue may appear as an encapsulated homogeneous extratesticular mass, isoechoic with the normal testis. Subtle hypoechoic nodules may be present in the mass. The presence of splenic tissue may be confirmed with a technetium-99m sulfur colloid scan.

Synostosis (plural: synostoses) is fusion of two bones. It can be normal in puberty, fusion of the epiphysis, or abnormal. When synostosis is abnormal it is a type of dysostosis.

Examples of synostoses include:

- craniosynostosis – an abnormal fusion of two or more cranial bones;

- radioulnar synostosis – the abnormal fusion of the radius and ulna bones of the forearm;

- tarsal coalition – a failure to separately form all seven bones of the tarsus (the hind part of the foot) resulting in an amalgamation of two bones; and

- syndactyly – the abnormal fusion of neighboring digits.

Synostosis within joints can cause ankylosis.