In right atrial isomerism, both atria of the heart are morphological right atria leading to associated abnormalities in the pulmonary venous system. In addition, individuals with right atrial isomerism develop asplenia, a midline liver, malrotation of the small intestine and the presence of two morphologic right lungs. Individuals with left atrial isomerism, by comparison, have two morphologic left atria, polysplenia, intestinal malrotation and two morphologic left lungs.

The majority of cases present at the time of birth or within a few days or weeks. Presenting signs and symptoms of the congenital heart defect may include cyanosis, breathlessness, lethargy and poor feeding.

The most commonly observed are congenital obstructive lesions of the left side of the heart, leading to reduced flow on this side of the heart. This includes bicuspid aortic valve and coarctation (narrowing) of the aorta. More than 50% of the cardiovascular malformations of individuals with Turner syndrome in one study were bicuspid aortic valves or coarctation of the aorta (usually preductal), alone or in combination.

Other congenital cardiovascular malformations, such as partial anomalous venous drainage and aortic valve stenosis or aortic regurgitation, are also more common in Turner syndrome than in the general population. Hypoplastic left heart syndrome represents the most severe reduction in left-sided structures.

Asplenia with cardiovascular anomalies, also known as Ivemark syndrome and right atrial isomerism, is an example of a heterotaxy syndrome. These uncommon congenital disorders are characterized by defects in the heart, spleen and paired organs such as the lungs and kidneys. Another name is "asplenia-cardiovascular defect-heterotaxy".

Right atrial isomerism is named for its discoverer, Swedish pathologist Biörn Ivemark.

Of the following common symptoms of Turner syndrome, an individual may have any combination of symptoms and is unlikely to have all symptoms.

- Short stature

- Lymphedema (swelling) of the hands and feet of a newborn

- Broad chest (shield chest) and widely spaced nipples

- Low posterior hairline

- Low-set ears

- Reproductive sterility

- Rudimentary ovaries gonadal streak (underdeveloped gonadal structures that later become fibrotic)

- Amenorrhoea, the absence of a menstrual period

- Increased weight, obesity

- Shortened metacarpal IV

- Small fingernails

- Characteristic facial features

- Webbed neck from cystic hygroma in infancy

- Aortic valve stenosis

- Coarctation of the aorta

- Bicuspid aortic valve (most common cardiac problem)

- Horseshoe kidney

- Visual impairments – sclera, cornea, glaucoma, etc.

- Ear infections and hearing loss

- High waist-to-hip ratio (the hips are not much bigger than the waist)

- Attention deficit hyperactivity disorder (problems with concentration, memory, attention with hyperactivity seen mostly in childhood and adolescence)

- Nonverbal learning disability (problems with maths, social skills, and spatial relations)

Other features may include a small lower jaw (micrognathia), cubitus valgus, soft upturned nails, palmar crease, and drooping eyelids. Less common are pigmented moles, hearing loss, and a high-arch palate (narrow maxilla). Turner syndrome manifests itself differently in each female affected by the condition; therefore, no two individuals share the same features.

While most of the physical findings are harmless, significant medical problems can be associated with the syndrome. Most of these significant conditions are treatable with surgery and medication.

There are frequent associated congenital anomalies all related to deviations in the development of anatomical asymmetries in early embryonic stages. These conditions considered together are called "polysplenia syndrome".

Associated conditions include heterotaxy syndrome, intestinal malrotation, situs inversus, biliary atresia, and several cardiac malformations. Associated cardiac conditions include dextrocardia, atrial situs ambiguus, ventricular inversion, and VA concordance with left posterior aorta.

Although present, the multiple small spleens are often ineffective; this is termed functional asplenia.

The most striking sign of Timothy syndrome is the co-occurrence of both syndactyly (~0.03% of births) and long QT syndrome (1% per year) in a single patient. Other common symptoms of Timothy syndrome are cardiac arrhythmia (94%), heart malformations (59%), autism or an autism spectrum disorder (80% who survive long enough for evaluation). Facial dysmorphologies such as flattened noses also occur in approximately half of patients. Children with this disorder have small teeth which, due to poor enamel coating, are prone to dental cavities and often require removal. The average age of death due to complications of these symptoms is 2.5 years.

Atypical Timothy syndrome has largely the same symptoms as the classical form. Differences in the atypical form are the lack of syndactyly, the presence of musculoskeletal problems (particularly hyperflexible joints), and atrial fibrillation. Patients with atypical Timothy syndrome also have more facial deformities, including protruding foreheads and tongues. Finally, one patient with atypical Timothy syndrome had a body development discrepancy wherein her upper body was normally developed (that of a 6-year-old) while her lower half resembled a 2- or 3-year-old.

Children with Timothy syndrome tend to be born via caesarean section due to fetal distress.

Of those fetuses that do survive to gestation and subsequent birth, common abnormalities may include:

- Nervous system

- Intellectual disability and motor disorder

- Microcephaly

- Holoprosencephaly (failure of the forebrain to divide properly).

- Structural eye defects, including microphthalmia, Peters' anomaly, cataract, iris or fundus (coloboma), retinal dysplasia or retinal detachment, sensory nystagmus, cortical visual loss, and optic nerve hypoplasia

- Meningomyelocele (a spinal defect)

- Musculoskeletal and cutaneous

- Polydactyly (extra digits)

- Cyclopia

- Proboscis

- Congenital trigger digits

- Low-set ears

- Prominent heel

- Deformed feet known as rocker-bottom feet

- Omphalocele (abdominal defect)

- Abnormal palm pattern

- Overlapping of fingers over thumb

- Cutis aplasia (missing portion of the skin/hair)

- Cleft palate

- Urogenital

- Abnormal genitalia

- Kidney defects

- Other

- Heart defects (ventricular septal defect) (Patent Ductus Arteriosus)

- Dextrocardia

- Single umbilical artery

Timothy syndrome is a rare autosomal dominant disorder characterized by physical malformations, as well as neurological and developmental defects, including heart QT-prolongation, heart arrhythmias, structural heart defects, syndactyly (webbing of fingers and toes) and autism spectrum disorders.

Timothy syndrome often ends in early childhood death.

It is characterized by developmental defects including cryptophthalmos (where the eyelids fail to separate in each eye), and malformations in the genitals (such as micropenis, cryptorchidism or clitoromegaly). Congenital malformations of the nose, ears, larynx and renal system, as well as mental retardation, manifest occasionally. Syndactyly (fused fingers or toes) has also been noted.

Polysplenia or Chaudhrey's disease is a congenital disease manifested by multiple small accessory spleens, rather than a single, full-sized, normal spleen. Polysplenia sometimes occurs alone, but it is often accompanied by other developmental abnormalities. Conditions associated with polysplenia include gastrointestinal abnormalities, such as intestinal malrotation or biliary atresia, as well as cardiac abnormalities, such as dextrocardia.

Heart-hand syndrome type 1 is more commonly known as Holt–Oram syndrome. Is the most prevalent form of heart-hand syndrome.

It is an autosomal dominant disorder that affects bones in the arms and hands (the upper limbs) and may also cause heart problems. The syndrome includes an absent radial bone in the arms, an atrial septal defect, and a first degree heart block.

There is no specific treatment or cure for individuals affected with this type of syndrome, though some of the abnormal physical features may be surgically correctable.

The classical triad of symptoms that defines 3C syndrome includes certain heart defects, hypoplasia (underdevelopment) of the cerebellum, and cranial dysmorphisms, which can take various forms. The heart defects and cranial dysmorphisms are heterogeneous in individuals who are all classed as having Ritscher-Schinzel syndrome.

Heart defects commonly seen with Ritscher-Schinzel syndrome are associated with the endocardial cushion and are the most important factor in determining a diagnosis. The mitral valve and tricuspid valve of the heart can be malformed, the atrioventricular canal can be complete instead of developing into the interatrial septum and interventricular septum, and conotruncal heart defects, which include tetralogy of Fallot, double outlet right ventricle, transposition of the great vessels, and hypoplastic left heart syndrome. Aortic stenosis and pulmonary stenosis have also been associated with 3C syndrome.

The cranial dysmorphisms associated with 3C syndrome are heterogeneous and include a degree of macrocephaly, a large anterior fontanel, a particularly prominent occiput and forehead, ocular hypertelorism (wide-set eyes), slanted palpebral fissures, cleft palate, a depressed nasal bridge, cleft palate with associated bifid uvula, low-set ears, micrognathia (an abnormally small jaw), brachycephaly (flattened head), and ocular coloboma. Low-set ears are the most common cranial dysmorphism seen in 3C syndrome, and ocular coloboma is the least common of the non-concurrent symptoms (cleft lip co-occurring with cleft palate is the least common).

Cranial dysplasias associated with 3C syndrome are also reflected in the brain. Besides the cerebellar hypoplasia, cysts are commonly found in the posterior cranial fossa, the ventricles and the cisterna magna are dilated/enlarged, and Dandy-Walker malformation is present. These are reflected in the developmental delays typical of the disease. 75% of children with 3C syndrome have Dandy-Walker malformation and hydrocephalus.

Signs and symptoms in other body systems are also associated with 3C syndrome. In the skeletal system, ribs may be absent, and hemivertebrae, syndactyly (fusion of fingers together), and clinodactyly (curvature of the fifth finger) may be present. In the GI and genitourinary systems, anal atresia, hypospadia (misplaced urethra), and hydronephrosis may exist. Adrenal hypoplasia and growth hormone deficiency are associated endocrine consequences of Ritscher-Schinzel syndrome. Some immunodeficiency has also been reported in connection with 3C syndrome.

Many children with the disorder die as infants due to severe congenital heart disease. The proband of Ritscher and Schinzel's original study was still alive at the age of 21.

A fetus with 3C syndrome may have an umbilical cord with one umbilical artery instead of two.

The most common symptoms of Williams syndrome are heart defects and unusual facial features. Other symptoms include failure to gain weight appropriately in infancy (failure to thrive) and low muscle tone. Individuals with Williams syndrome tend to have widely spaced teeth, a long philtrum, and a flattened nasal bridge.

Most individuals with Williams syndrome are highly verbal relative to their IQ, and are overly sociable, having what has been described as a "cocktail party" type personality. Individuals with WS hyperfocus on the eyes of others in social engagements.

There is a range of signs and symptoms including cleft lip or palate, mental retardation and various forms of ectodermal dysplasia. Additional symptoms may include fused eyelids, absent nails, delayed bone growth and dry skin. It is believed that this syndrome follows an autosomal dominant pattern of inheritance with incomplete penetrance, and caused by a mutation affecting the TP63 gene. It has been suggested that this syndrome, AEC syndrome and Rapp–Hodgkin syndrome may be variations of the same disease.

Bannayan–Riley–Ruvalcaba syndrome is associated with enlarged head and benign mesodermal hamartomas (multiple hemangiomas, and intestinal polyps). Dysmorphy as well as delayed neuropsychomotor development can also be present. The head enlargement does not cause widening of the ventricles or raised intracranial pressure; these individuals have a higher risk of developing tumors, as the gene involved in BRRs is phosphatase and tensin homologue.

Some individuals have thyroid issues consistent with multinodular goiter, thyroid adenoma, differentiated non-medullary thyroid cancer,

most lesions are slowly growing. Visceral as well as intracranial involvement may occur in some cases, and can cause bleeding and symptomatic mechanical compression

There are a variety of clinical manifestations of situs ambiguous. Acute symptoms can be due to both cardiac and non-cardiac defects. Cyanosis or blue skin coloration, primarily affecting the lips and fingernails, can indicate a systemic or circulatory issue. Poor feeding, failure to thrive, and rapid shallow breathing may also be observed due to poor circulation. Upon examination, arrhythmia and heart murmur may raise further suspicion of a cardiac abnormality. Non-cardiac symptoms include impairments of the liver and gastrointestinal tract. Biliary atresia, or inflammation and destruction of the bile ducts, may lead to jaundice. Vomiting and swelling of the abdominal region are features that suggest improper positioning of the intestines. Poor positioning of the intestine also makes it more prone to blockage, which can result in numerous chronic health issues. Asplenia and polysplenia are also possible features of heterotaxy syndrome.

Due to abnormal cardiac development, patients with situs ambiguous usually develop right atrial isomerism consisting of 2 bilaterally paired right atria, or left atrial isomerism consisting of 2 bilaterally paired left atria. Clinical features and symptoms can vary dependent upon assignment of left versus right atrial isomerism. In either instance, the apex of the heart will be poorly positioned, which should alert a clinician of the likelihood of atrial isomerism. It is estimated that 5-10% of isomeric patients have mesocardia, in which the heart is positioned at the center of the thorax, 25-50% have dextrocardia, in which the apex of the heart is pointed toward the right side of the thorax, and 50 - 70% have levocardia, in which the apex of the heart is pointed toward the left side of the thorax.

Patau syndrome is a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13. The extra genetic material disrupts normal development, causing multiple and complex organ defects.

This can occur either because each cell contains a full extra copy of chromosome 13 (a disorder known as trisomy 13 or trisomy D), or because each cell contains an extra partial copy of the chromosome (i.e., Robertsonian translocation) or because of mosaic Patau syndrome. Full trisomy 13 is caused by nondisjunction of chromosomes during meiosis (the mosaic form is caused by nondisjunction during mitosis).

Like all nondisjunction conditions (such as Down syndrome and Edwards syndrome), the risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average. Patau syndrome affects somewhere between 1 in 10,000 and 1 in 21,700 live births.

Perlman syndrome (PS) (also called renal hamartomas, nephroblastomatosis and fetal gigantism) is a rare overgrowth disorder present at birth. It is characterized by polyhydramnios and fetal overgrowth, including macrocephaly, neonatal macrosomia, visceromegaly, dysmorphic facial features, and an increased risk for Wilms' tumor at an early age. The prognosis for Perlman syndrome is poor and it is associated with a high neonatal mortality.

Fraser syndrome (also known as Meyer-Schwickerath's syndrome, Fraser-François syndrome, or Ullrich-Feichtiger syndrome) is an autosomal recessive congenital disorder. Fraser syndrome is named for the geneticist George R. Fraser, who first described the syndrome in 1962.

There is an overlap in symptoms between 3C syndrome and Joubert syndrome. Joubert syndrome often manifests with similar cerebellar hypoplasia and its sequelae, including hyperpnea, ataxia, changes in eye movement, and cleft lip and palate. Occasionally, Joubert syndrome will include heart malformations. Brachmann-de Lange syndrome must also be differentiated from 3C syndrome. It presents with similar craniofacial and heart abnormalities and can include Dandy-Walker phenotype, making it difficult to distinguish. Dandy-Walker malformation is also occasionally seen in Ellis-van Creveld syndrome, which is characterized by heart defects and malformed alveolar ridge. Many disorders include the Dandy-Walker phenotype and thus it is not pathognomonic for 3C syndrome.

CHARGE syndrome can also be misdiagnosed. This is because both CHARGE syndrome and 3C syndrome share symptoms of ocular colobomas, cardiac defects, growth retardation, and minor facial abnormalities.

Coffin-Siris syndrome presents with fifth-finger deformities and congenital heart defects. It is distinguished from 3C syndrome by differences in facial dysmorphisms.

Pashayan syndrome also known as Pashayan–Prozansky Syndrome, and blepharo-naso-facial syndrome is a rare syndrome. Facial abnormalities characterise this syndrome as well as malformation of extremities. Specific characteristics would be a bulky, flattened nose, where the face has a mask like appearance and the ears are also malformed.

A subset of Pashayan syndrome has also been described, known as "cerebrofacioarticular syndrome", "Van Maldergem syndrome'" or "Van Maldergem–Wetzburger–Verloes syndrome". Similar symptoms are noted in these cases as in Pashayan syndrome.

Multiple hamartoma syndrome is a syndrome characterized by more than one hamartoma.

It is sometimes equated with Cowden syndrome. However, MeSH also includes Bannayan–Zonana syndrome (that is, Bannayan–Riley–Ruvalcaba syndrome) and Lhermitte–Duclos disease under this description. Some articles include Cowden syndrome, Bannayan–Riley–Ruvalcaba syndrome, and at least some forms of Proteus syndrome and Proteus-like syndrome under the umbrella term PTEN hamartoma tumor syndromes (PHTS).

Situs ambiguus or situs ambiguous, also known as heterotaxy or heterotaxia, is a rare congenital defect in which the major visceral organs are distributed abnormally within the chest and abdomen. Heterotaxy in general refers to any defect of left-right laterality and arrangement of the visceral organs. This does not include the congenital defect situs inversus, which results when arrangement of the organs in the abdomen and chest are mirrored, so the positions are opposite the normal placement. Situs inversus is the mirror image of situs solitus, which is normal asymmetric distribution of the abdominothoracic visceral organs. Patients with situs ambiguous are considered isomeric in that they have organs with two right-sides or two left-sides, most commonly observed in relation to the atria of the heart.

Individuals with situs inversus or situs solitus do not experience fatal dysfunction of their organ systems, as general anatomy and morphology of the abdominothoracic organ-vessel systems are conserved. Due to abnormal arrangement of organs in situs ambiguous, orientation across the left-right axis of the body is disrupted early in fetal development, resulting in severely flawed cardiac development and function in 50–80% of cases. They also experience complications with systemic and pulmonary blood vessels, significant morbidity, and sometimes death. All patients with situs ambiguus lack lateralization and symmetry of organs in the abdominal and thoracic cavities and are clinically considered to have a form of heterotaxy syndrome.

Heterotaxy syndrome with atrial isomerism occurs in 1 out of every 10,000 live births and is associated with approximately 3% of congenital heart disease cases. Additional estimation of incidence and prevalence of isomerism proves difficult due to failure to diagnose and underestimation of the disease by clinicians. Furthermore, right isomerism is much more easily recognized than left isomerism, contributing to the failure to diagnose.

Situs ambiguous is a growing field of research with findings dating back to 1973.

Little is known about the natural history of Roberts syndrome due to its wide clinical variability. The prognosis of the disease depends on the malformations, as the severity of the malformations correlates with survival. The cause of death for most fatalities of Roberts syndrome have not been reported; however, five deaths were reportedly due to infection.

The following are observations that have been made in individuals with cytogenetic findings of PCS/HR or ESCO2 mutations:

- The symptom of prenatal growth retardation is the most common finding and can be moderate to severe. Postnatal growth retardation can also be moderate to severe and correlates with the degree of severity of limb and craniofacial malformations.

- In limb malformations, the upper limbs are typically more severely affected than the lower limbs. There have been many cases of only upper limb malformation.

- In hand malformations, the thumb is most often affected, followed by the fifth finger (the little finger). In severe cases, the patient may only have three fingers and in rare cases only one.

- In craniofacial malformations, mildly affected individuals will have no abnormalities of the palate. The most severely affected will have a fronto-ethmoid-nasal-maxillary encephalocele.

- The severity of limb malformations and craniofacial malformations is correlated.

- Other abnormalities can occur in different parts of the body, including:

- Heart- atrial septal defects, ventricular septal defects, patent ductus arteriosus

- Kidneys- polycystic kidney, horseshoe kidney

- Male Genitals- enlarged penis, cryptorchidism

- Female Genitals- enlarged clitoris

- Hair- sparse, silvery-blonde scalp hair

- Cranial Nerve Paralysis, Moyamoya disease, Stroke, Intellectual disability