The syndrome gets its name from the characteristic cry of affected infants, which is similar to that of a meowing kitten, due to problems with the larynx and nervous system. About 1/3 of children lose the cry by age of 2 years. Other symptoms of cri du chat syndrome may include:

- feeding problems because of difficulty in swallowing and sucking;

- low birth weight and poor growth;

- severe cognitive, speech, and motor delays;

- behavioral problems such as hyperactivity, aggression, outbursts, and repetitive movements;

- unusual facial features which may change over time;

- excessive drooling;

- small head and jaw;

- wide eyes;

- skin tags in front of eyes.

Other common findings include hypotonia, microcephaly, growth retardation, a round face with full cheeks, hypertelorism, epicanthal folds, down-slanting palpebral fissures, strabismus, flat nasal bridge, down-turned mouth, micrognathia, low-set ears, short fingers, single palmar creases, and cardiac defects (e.g., ventricular septal defect [VSD], atrial septal defect [ASD], patent ductus arteriosus [PDA], tetralogy of Fallot). Infertility is not associated with Cri du chat.

It has also been observed that people with the condition have difficulties communicating. While levels of proficiency can range from a few words to short sentences, it is often recommended by medical professionals for the child to undergo some sort of speech therapy/aid with the help of a professional.

Less frequently encountered findings include cleft lip and palate, preauricular tags and fistulas, thymic dysplasia, intestinal malrotation, megacolon, inguinal hernia, dislocated hips, cryptorchidism, hypospadias, rare renal malformations (e.g., horseshoe kidneys, renal ectopia or agenesis, hydronephrosis), clinodactyly of the fifth fingers, talipes equinovarus, pes planus, syndactyly of the second and third fingers and toes, oligosyndactyly, and hyperextensible joints. The syndrome may also include various dermatoglyphics, including transverse flexion creases, distal axial triradius, increased whorls and arches on digits, and a single palmar crease.

Late childhood and adolescence findings include significant intellectual disability, microcephaly, coarsening of facial features, prominent supraorbital ridges, deep-set eyes, hypoplastic nasal bridge, severe malocclusion, and scoliosis.

Affected females reach puberty, develop secondary sex characteristics, and menstruate at the usual time. The genital tract is usually normal in females except for a report of a bicornuate uterus. In males, testes are often small, but spermatogenesis is thought to be normal.

Affected individuals present with a broad array of medical and behavioral manifestations (tables 1 and 2). Patients are consistently characterized by global developmental delay, intellectual disability, speech abnormalities, ASD-like behaviors, hypotonia and mild dysmorphic features. Table 1 summarizes the dysmorphic and medical conditions that have been reported in individuals with PMS. Table 2 summarize the psychiatric and neurological associated with PMS. Most of the studies include small samples or relied on parental report or medical record review to collect information, which can account in part for the variability in the presentation of some of the presenting features. Larger prospective studies are needed to further characterize the phenotype.

Table 1: Dysmorphic features and medical comorbid conditions that have been reported in individuals with Phelan McDermid Syndrome.

Table 2: Psychiatric and Neurologic Manifestations associated with Phelan McDermid Syndrome

Following are the features and characteristics that help in spotting this disorder:

- Low birth weight (usually under 5 pounds/2.5 kilograms)

- Delayed growth and small stature

- Developmental delay

- Limb differences (missing limbs or portions of limbs)

- Small head size (microcephaly)

- Thick eyebrows, which typically meet at midline (synophrys)

- Long eyelashes

- Short upturned nose and thin downturned lips

- Long philtrum

- Excessive body hair

- Small hands and feet

- Small widely spaced teeth

- Low-set ears

- Hearing impairments

- Vision abnormalities (e.g., ptosis, nystagmus, high myopia, hypertropia)

- Partial joining of the second and third toes

- Incurved 5th fingers (clinodactyly)

- Gastroesophageal reflux

- Seizures

- Heart defects (e.g., pulmonary stenosis, VSD, ASD, coarctation of the aorta)

- Cleft palate

- Feeding problems

- Hypoplastic genitalia

Children with this syndrome are often found to have long eyelashes, bushy eyebrows and synophrys (joined eyebrows). Body hair can be excessive and affected individuals are often shorter than their immediate family members. They present a characteristic facial phenotype and is recognizable with the Facial Dysmorphology Novel Analysis (FDNA) technology

CdLS can give rise to its own array of complexities. Children with CdLS often suffer from gastrointestinal tract difficulties, particularly gastroesophageal reflux. Vomiting, intermittent poor appetite, constipation, diarrhea or gaseous distention are known to be a regularity in cases where the GI tract problems are acute. Symptoms may range from mild to severe.

CdLS may include behavior problems, including self-stimulation, aggression, self-injury or strong preference to a structured routine. Many children with CdLS exhibit autistic-like behaviors.

Behavior problems in CdLS are not inevitable. Many behavior issues associated with CdLS are reactive (i.e., something happens within the person's body or environment to bring on the behavior) and cyclical (comes and goes). Often, an underlying medical issue causes a change in behavior. Once the medical issue is treated, the behavior diminishes.

The most common characteristics include a distinct craniofacial phenotype (microcephaly, micrognathia, short philtrum, prominent glabella, ocular hypertelorism, dysplastic ears and periauricular tags), growth restriction, intellectual disability, muscle hypotonia, seizures, and congenital heart defects. Less common characteristics include hypospadias, colobomata of the iris, renal anomalies, and deafness. Antibody deficiencies are also common, including common variable immunodeficiency and IgA deficiency. T-cell immunity is normal.

Cri du chat syndrome, also known as chromosome 5p deletion syndrome, 5p− syndrome (pronounced "Five P Minus") or Lejeune’s syndrome, is a rare genetic disorder due to chromosome deletion on chromosome 5. Its name is a French term ("cat-cry" or "call of the cat") referring to the characteristic cat-like cry of affected children. It was first described by Jérôme Lejeune in 1963. The condition affects an estimated 1 in 50,000 live births across all ethnicities and is more common in females by a 4:3 ratio.

22q13 deletion syndrome (spoken as "twenty-two q one three", see Locus (genetics)) is a genetic disorder caused by deletions or rearrangements on the q terminal end (long arm) of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) typical of a terminal deletion may be diagnosed as 22q13 deletion syndrome. 22q13 deletion syndrome is often called Phelan-McDermid syndrome (abbreviated PMS). There is disagreement among researchers as to the exact definition of 22q13 deletion syndrome. The Developmental Synaptopathies Consortium defines PMS as being caused by "SHANK3" mutations, a definition that appears to exclude terminal deletions. The requirement to include "SHANK3" in the definition is supported by many, but not by those who first described 22q13 deletion syndrome.

A prototypical terminal deletion of 22q13 can be uncovered by karyotype analysis, but many terminal and interstitial deletions are too small. The availability of DNA microarray technology for revealing multiple genetic problems simultaneously has been the diagnostic tool of choice. The falling cost for whole exome sequencing and, eventually, whole genome sequencing, may replace DNA microarray technology for candidate evaluation. However, fluorescence in situ hybridization (FISH) tests remain valuable for diagnosing cases of mosaicism (mosaic genetics) and chromosomal rearrangements (e.g., ring chromosome, unbalanced chromosomal translocation). Although early researchers sought a monogenic (single gene genetic disorder) explanation, recent studies have not supported that hypothesis (see Etiology, below).

Wolf–Hirschhorn syndrome (WHS), also known as chromosome deletion Dillan 4p syndrome, Pitt–Rogers–Danks syndrome (PRDS) or Pitt syndrome, was first described in 1961 by Americans Herbert L. Cooper and Kurt Hirschhorn and, thereafter, gained worldwide attention by publications by the German Ulrich Wolf, and Hirschhorn and their co-workers, specifically their articles in the German scientific magazine "Humangenetik". It is a characteristic phenotype resulting from a partial deletion of chromosomal material of the short arm of chromosome 4 (del(4p16.3)).

Cornelia de Lange Syndrome (CdLS) is a very rare genetic disorder present from birth, but not always diagnosed at birth. It causes a range of physical, cognitive, and medical challenges and affects both sexes equally. The syndrome is named after Dutch pediatrician Cornelia Catharina de Lange, who described it.

It is often termed Bushy Syndrome and is also known as Amsterdam dwarfism. It is a genetic disorder that can lead to severe developmental anomalies. It affects the physical and intellectual development of a child. Exact incidence is unknown, but it is estimated at 1 in 10,000 to 30,000.

The phenotypic data on 11 patients indicated that cases are not always ascertained for CHD but that CHD was the most common single feature found in 6 out of 11 individuals. Developmental delay and/or learning difficulties were found in 5 out of 11 cases, but one prenatal case was developing normally at 15 months of age (Case 1,). Three other prenatal cases could not yet be reliably assessed. A variable degree of facial dysmorphism was present in 5 out of 11 individuals. Partial toe syndactyly has been found in one mother and son diad and adrenal anomalies in two probands but not in the duplicated mother of one of them. The phenotype is compatible with independent adult life with varying degrees of support.

Duplication of the GATA4 transcription factor () is believed to underlie the congenital heart disease and other genes, common to the duplication and deletion syndromes, can be regarded as candidates for the 8p23.1 duplication syndrome. These include the SOX7 transcription factor () for both CHD and developmental delay and the TNKS gene () for behavioural difficulties. The diaphragmatic hernia found in the 8p23.1 deletion syndrome has not been found in the 8p23.1 duplication syndrome to date.

The duplication may be associated with copy number changes of the adjacent olfactory receptor/defensin repeats (ORDRs) that predispose to the 8p23.1 deletion and duplication syndromes. High total copy numbers of these repeats have been associated with predisposition to psoriasis and low copy number with predisposition to Crohn's disease.

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

8p23.1 duplication syndrome is a rare genetic disorder caused by a duplication of a region from human chromosome 8. This duplication syndrome has an estimated prevalence of 1 in 64,000 births and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable phenotype including one or more of speech delay, developmental delay, mild dysmorphism, with prominent forehead and arched eyebrows, and congenital heart disease (CHD).

De Barsy syndrome is a rare autosomal recessive genetic disorder. Symptoms include cutis laxa (loose hanging skin) as well as other eye, musculoskeletal, and neurological abnormalities. It is usually progressive, manifesting side effects that can include clouded corneas, cataracts, short stature, dystonia, or progeria (premature aging).

It was first described in 1967 by De Barsy et al. and, as of 2011, there have been 27 cases reported worldwide. The genes that cause De Barsy syndrome have not been identified yet, although several studies have narrowed down the symptoms' cause. A study by Reversade et al. has shown that a mutation in PYCR1, the genetic sequence that codes for mitochondrial enzymes that break down proline, are prevalent in cases of autosomal recessive cutis laxa (ARCL), a condition very similar to De Barsy syndrome. A study by Leao-Teles et al. has shown that De Barsy syndrome may be related to mutations in ATP6V0A2 gene, known as ATP6V0A2-CDG by the new naming system.

Alternative names for De Barsy syndrome include corneal clouding-cutis laxa-mental retardation, cutis laxa-growth deficiency syndrome, De Barsy–Moens–Diercks syndrome, and progeroid syndrome of De Barsy.

The following is a list of symptoms that have been associated with Roberts syndrome:

- Bilateral Symmetric Tetraphocomelia- a birth defect in which the hands and feet are attached to shortened arms and legs

- Prenatal Growth Retardation

- Hypomelia (Hypoplasia)- the incomplete development of a tissue or organ; less drastic than aplasia, which is no development at all

- Oligodactyly- fewer than normal number of fingers or toes

- Thumb Aplasia- the absence of a thumb

- Syndactyly- condition in which two or more fingers (or toes) are joined together; the joining can involve the bones or just the skin between the fingers

- Clinodactyly- curving of the fifth finger (little finger) towards the fourth finger (ring finger) due to the underdevelopment of the middle bone in the fifth finger

- Elbow/Knee Flexion Contractures- an inability to fully straighten the arm or leg

- Cleft Lip- the presence of one or two vertical fissures in the upper lip; can be on one side (unilateral) or on both sides (bilateral)

- Cleft Palate- opening in the roof of the mouth

- Premaxillary Protrusion- upper part of the mouth sticks out farther than the lower part of the mouth

- Micrognathia- small chin

- Microbrachycephaly- smaller than normal head size

- Malar Hypoplasia- underdevelopment of the cheek bones

- Downslanting Palpebral Fissures- the outer corners of the eyes point downwards

- Ocular Hypertelorism- unusually wide-set eyes

- Exophthalmos- a protruding eyeball

- Corneal Clouding- clouding of the front-most part of the eye

- Hypoplastic Nasal Alae- narrowing of the nostrils that can decrease the width of the nasal base

- Beaked Nose- a nose with a prominent bridge that gives it the appearance of being curved

- Ear Malformations

- Intellectual disability

- Encephalocele (only in severe cases)- rare defect of the neural tube characterized by sac-like protrusions of the brain

Mortality is high among those severely affected by Roberts syndrome; however, mildly affected individuals may survive to adulthood

Bohring–Opitz syndrome (BOS) is a medical syndrome caused by a mutation in the ASXL1 gene. It is diagnosed by genetic testing and is characterised by characteristic craniofacial appearance, fixed contractures of the upper limbs, abnormal posture, feeding difficulties, intellectual disability, small size at birth, and failure to thrive. Some of these features are shared with other genetic syndromes.

Genetically, de novo truncating mutations in ASXL1 have been shown to account for approximately 50% of Bohring–Opitz syndrome cases.

The syndrome is extremely rare, with fewer than 80 known cases worldwide. The leading cause of death is respiratory infections. Children with BOS can have feeding difficulties, recurring respiratory infections, sleep apnea, developmental delay, failure to thrive, abnormal hair density and length, Wilm’s Tumors, brain abnormalities, silent aspiration, and other issues.

Along with the four aspects of the disorder that give it its name, there are also other common symptoms:

- A downward slant of the forehead

- Delayed bone maturation

- Mental retardation

The ocular abnormalities are generally retinal coloboma and nystagmus.

The syndrome is a rare clinical disorder.

- Physical

- Overgrowth

- Accelerated skeletal maturation

- Dysmorphic facial features

- Prominent eyes

- Bluish sclerae

- Coarse eyebrows

- Upturned nose

- Radiologic examination

- Accelerated osseous maturation

- Phalangeal abnormalities

- Tubular thinning of the long bones

- Skull abnormalities

- Mental

- Often associated with intellectual disability (of variable degree)

Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques. Smaller deletions result in Microdeletion syndrome, which are detected using fluorescence in situ hybridization (FISH)

Examples of chromosomal deletion syndromes include 5p-Deletion (cri du chat syndrome), 4p-Deletion (Wolf-Hirschhorn syndrome), Prader–Willi syndrome, and Angelman syndrome.

Approximately 100 cases have been described in the literature to date.

The facial features are characteristic and include

- Deep set eyes

- Strabismus

- Myopia

- Marked nasal root

- Broad and/or beaked nasal bridge

- Prominent Cupid's bow

- Everted lower lip

- Tented upper lip

- Large mouth

- Widely spaced teeth

- Wide and shallow palate

- Ears with thick and overfolded helix

Most have a smiling appearance.

Intellectual disability is severe. Language is absent or limited to only a few words. Stereotypic movements particularly of the arms, wrists and fingers is almost universal. Hypotonia is common (75%) as is an unsteady gait. All have delayed walking. Other features include a single (simian) palmar crease, long, slender fingers, flat feet and cryptorchidism (in males). Finger clubbing and the presence of fetal pads is common. Hyperventilation occurs in over half and is frequently followed by apnea and cyanosis. During these episodes aerophagia may occur. Constipation is common. Microcephaly and seizures may occur. Hypopigmented skin macules have occasionally been reported.

Differential diagnosis includes Angelman syndrome, Mowat–Wilson syndrome and Rett syndrome.

Persons affected are cognitively impaired and have behavioral disturbances that emerge between two and three years of age. The uncontrollable self-injury associated with LNS also usually begins at three years of age. The self-injury begins with biting of the lips and tongue; as the disease progresses, affected individuals frequently develop finger biting and head banging. The self-injury can increase during times of stress. Self-harm is a distinguishing characteristic of the disease and is apparent in 85% of affected males.

The majority of individuals are cognitively impaired, which is sometimes difficult to distinguish from other symptoms because of the behavioral disturbances and motor deficits associated with the syndrome. In many ways, the behaviors may be seen as a psychological extension of the compulsion to cause self-injury, and include rejecting desired treats or travel, repaying kindness with coldness or rage, failing to answer test questions correctly despite study and a desire to succeed, provoking anger from caregivers when affection is desired.

Compulsive behaviors also occur, including aggressiveness, vomiting, spitting, and coprolalia (involuntary swearing). The development of this type of behavior is sometimes seen within the first year, or in early childhood, but others may not develop it until later in life.

The periods before and surrounding birth are typically normal in individuals with LNS. The most common presenting features are abnormally decreased muscle tone (hypotonia) and developmental delay, which are evident by three to six months of age. Affected individuals are late in sitting up, while most never crawl or walk. Lack of speech is also a very common trait associated with LNS.

Irritability is most often noticed along with the first signs of nervous system impairment. Within the first few years of life, extrapyramidal involvement causes abnormal involuntary muscle contractions such as loss of motor control (dystonia), writhing motions (choreoathetosis), and arching of the spine (opisthotonus). Signs of pyramidal system involvement, including spasticity, overactive reflexes (hyperreflexia) and extensor plantar reflexes, also occur. The resemblance to athetoid cerebral palsy is apparent in the neurologic aspects of LNS. As a result, most individuals are initially diagnosed as having cerebral palsy. The motor disability is so extensive that most individuals never walk, and become lifelong wheelchair users.

A triad of hypokalemic periodic paralysis, potentially fatal cardiac ventricular ectopy and characteristic physical features is known as Anderson-Tawil Syndrome. It affects the heart, symptoms are a disruption in the rhythm of the heart's lower chambers (ventricular arrhythmia) in addition to the symptoms of long QT syndrome. There are also physical abnormalities associated with Andersen–Tawil syndrome, these typically affect the head, face, and limbs. These features often include an unusually small lower jaw (micrognathia), low-set ears, and an abnormal curvature of the fingers called clinodactyly. Furthermore it causes symptoms which are similar to Long QT syndrome, which Andersen's is also known as. Long QT syndrome, a hereditary disorder that usually affects children or young adults, slows the signal that causes the ventricles to contract. Another electrical signal problem, atrial flutter, happens when a single electrical wave circulates rapidly in the atrium, causing a very fast but steady heartbeat. Heart block involves weak or improperly conducted electrical signals from the upper chambers that can't make it to the lower chambers, causing the heart to beat too slowly. These conditions can put you at risk for cardiac arrest. Treatment might involve medication, ablation, or an implanted device to correct the misfiring, such as a pacemaker or defibrillator. Here are some common physical abnormalities, but keep in mind these do vary (in severity) between each patient:

Some more severe issues can be caused via the potassium channelopathy. These include paralysis (mostly temporary and can last from several seconds to several minutes), inability to perform long distance/interval exercises and sudden exhaustion- although this can be a sign of cardiac arrhythmia- which should be immeditaley checked out by a GP, whether you have been diagnosed with ATS or not.

The most notable features of Wilson-Turner Syndrome are intellectual disability, obesity, hypogonadism, gynecomastia, and distinct facial features. All of the symptoms are chronic. Affected females are known to have less severe signs and symptoms than males. Female carriers of the disorder may have none or mild symptoms.

- Intellectual Disability is the limitation in an individual's mental functioning and skills. Patients of Wilson-Turner Syndrome have mental disability generally ranging from mild to severe, more frequently on the former. This symptom often coincides with delay in speech development and the occurrence of mood swings. Most males were noted to have a quiet and a cheerful disposition. However, individuals who displayed aggression and became easily upset were also seen. Children will display a delay in speech development often combined with excessive drooling and low voice tone. Some of the studied male patients had speech impairment ranging from little or no speech to minor stuttering.

- Obesity is the accumulation of excess fat on the body. Individuals with Wilson-Turner Syndrome are characterized to have truncal obesity, meaning the fat has accumulated in one's middle. Truncal obesity is often related to heart disease, kidney disease, and lowered blood immune system. Truncal obesity in this disorder becomes more apparent around the age of puberty.

- Tapered fingers is when one end of the finger is diminished in thickness, causing the ends of the fingers to appear pointed. This deformity is not debilitating in any particular manner. In addition to tapered fingers, both hands and feet tend to be small. Some males were observed to have pes planus, also known as flat feet.

- Hypogonadism is a condition in which the gonads have a decrease in function. This condition may result from the lack of sex hormone synthesis, such as androgen and estrogen. Hormones produced by the gonads may also decrease. Hypogonadism also influences the onset of other conditions of the Wilson-Turner Syndrome, such as gynecomastia and decreased testes size in males. It can also cause short stature in men and women. In addition to little genital development, pubic and body hair are scant.

- Some of the facial features that are associated with Wilson-Turner Syndrome include small head circumference, high forehead, prominent ears, and nose with a flattened bridge. There have been cases of a moderately high palate. Low muscle tone and subcutaneous swelling in facial tissue has also been noted. Thick eyebrows are also common. However, there has been reported cases where individuals had none of the mentioned facial features, which shows phenotypic abnormalities have possible environmental influences.

- Gynecomastia is a non-cancerous increase in male breast tissue. It is believed that disturbances in the endocrine system leads to an increase in estrogen and androgen hormones lead to the development of gynecomastia. A key feature of gynecomastia is a rubbery or firm glandular subcutaneous chest tissue that is palpated under the areola of the nipple, instead of the soft fatty tissue. There can also be in increase in diameter of the areola asymmetry in the chest tissue. The breast enlargement can occur in one or both side. Similar to truncal obesity, gynecomastia becomes apparent around the age of puberty.

Wilson-Turner Syndrome (WTS), also known as Mental Retardation X Linked Syndromic 6 (MRXS6), or Mental Retardation X Linked with Gynecomastia and Obesity is a congenital condition characterized by intellectual disability and associated with childhood-onset obesity. It is found to be linked to the X chromosome and caused by a mutation in the HDAC8 gene, which is located on the q arm at locus 13.1. Individuals with Wilson–Turner syndrome have a spectrum of physical characteristics including dysmorphic facial feature, hypogonadism, and short stature. Females generally have milder phenotype than males. The study of X-linked mental retardation began in 1943 when Martin and Bell reported a family exhibiting sex-linked mental retardation. However, this syndrome was not recognized until 1991. Wilson studied 14 males from 3 successive generations that presented hypogonadism, mental retardation, gynecomastia, short stature, among other symptoms. Eventually, this disorder was ruled distinct from a syndrome presented by Prader and Willi (Prader-Willi syndrome) because of its mode of inheritance, gynecomastia, and presence of small hands and feet. However, there are some speculations that this syndrome is in the same spectrum as the Cornelia de Lange syndrome. This disorder affects all demographics equally and is seen in less than one in one million people.

Respiratory complications are often cause of death in early infancy.