People with Renpenning's typically begin learning language at an ordinary pace, but by the age of 3–4 they experience a regression in mental and physical development, such as mild low muscle tone resulting in elongated faces and rapid loss in the normal growth of the head (microcephaly). Small testes and short stature are also known to commonly occur.

Microcephaly is a disorder in which the circumference of the head is smaller than average for the person's age and gender. Most children with microcephaly also have a smaller than typical brain and intellectual disability. Some of the most common signs and symptoms associated with microcephaly are seizures, poor feeding, high pitched cry, intellectual disability, developmental delay, and increased movement of arms and legs.

Common signs of Say–Meyer syndrome are trigonocephaly as well as head and neck symptoms. The head and neck symptoms come in the form of craniosynostosis affecting the metopic suture (the dense connective tissue structure that divides the two halves of the skull in children which usually fuse together by the age of six). Symptoms of Say–Meyer syndrome other than developmental delay and short stature include

- Intellectual disability.

- Low-set ears/posteriorly rotated ears

- Intellectual deficit as well as learning disability

- Intrauterine growth retardation (poor growth of a baby while it is in the mother's womb)

- Posterior fontanel

- Premature synostosis of the lambdoid suture (the fusion of the bones to the joint is premature)

- Narrow forehead

- Trigonocephaly (a frontal bone anomaly that is characterized by a premature fusion of the bones which gives the forehead a triangular shape)

- Hypotelorism or hypertelorism (reduced or increased width between the eyes)

- Craniosynostosis (when one or more seam-like junctions between two bones fuses by turning into bone. This changes the growth pattern of the skull)

- Low birth weight and height

The affected patients sometimes show a highly arched palate, clinodactyly (a defect in which toes or fingers are positioned abnormally) and ventricular septal defect (a heart defect that allows blood to pass directly from left to the right ventricle which is caused by an opening in the septum). Overall, Say–Meyer syndrome impairs growth, motor function, and mental state.

Vision abnormalities in children with 1p36 have been wide-ranging, including:

Children with Weaver syndrome tend to look similar and have distinctive physical and craniofacial characteristics, which may include several, but not all of the following features:

- Macrocephaly

- Large bifrontal diameter

- Flattened occiput

- Long philtrum

- Retrognathia

- Round face in infancy

- Prominent chin crease

- Large ears

- Strabismus

- Hypertelorism

- Epicanthal folds

- Downslanting palpebral fissures

Other features may include loose skin, thin deep-set nails, thin hair, short ribs, limited elbow and knee extension, camptodactyly, and a coarse, low-pitched voice. Delayed development of motor skills such as sitting, standing, and walking are commonly exhibited in early childhood. Patients with Weaver syndrome typically have mild intellectual disability with poor coordination and balance. They also have some neurological abnormalities such as speech delay, epilepsy, intellectual disability, hypotonia or hypertonia, and behavioral problems.

Renpenning's syndrome is a neurodevelopmental disorder recognised in males that causes intellectual disability, mild growth retardation with examples in the testes and head, and a somewhat short stature. The condition only affects males, starting at birth, and was first characterized in 1962. but first described by Hans Renpenning in 1963 after he documented these traits on many children in one family alone.

It can be associated with "PQBP1".

SFMS affects the skeletal and nervous system. This syndrome's external signs would be an unusual facial appearance with their heads being slightly smaller and unusually shaped, a narrow face which is also called dolichocephaly, a large mouth with a drooping lower lip that are held open, protruding upper jaw, widely spaced upper front teeth, an underdeveloped chin, cleft palate and exotropied-slanted eyes with drooping eyelids.

Males who have SFMS have short stature and a thin body build. Also skin is lightly pigmented with multiple freckles. They may have scoliosis and chest abnormalities.

Affected boys have reduced muscle tone as infants and young children. X-rays sometimes show that their bones are underdeveloped and show characteristics of younger bones of children. Boys usually under the age of 10 have reduced muscle tone but later, patients with SFMS over the age of 10 have increased muscle tone and reflexes that cause spasticity. Their hands are short with unusual palm creases with short, shaped fingers and foot abnormalities are shortened and have fused toes and usually mild.

They have an absent of a spleen and the genitals may also show undescended testes ranging from mild to severe that leads to female gender assignment.

People who have SFMS have severe mental retardation. They are sometimes restless, behavior problems, seizures and severe delay in language development. They are self-absorbed with reduced ability to socialize with others around them. They also have psychomotor retardation which is the slowing-down of thoughts and a reduction of physical movements. They have cortical atrophy or degeneration of the brain's outer layer. Cortical atrophy is usually founded in older affected people.

Genitopatellar syndrome is a rare condition characterized by genital abnormalities, missing or underdeveloped kneecaps (patellae), intellectual disability, and abnormalities affecting other parts of the body.

Genitopatellar syndrome is also associated with delayed development and intellectual disability, which are often severe. Affected individuals may have an unusually small head (microcephaly) and structural brain abnormalities, including underdeveloped or absent tissue connecting the left and right halves of the brain (agenesis of the corpus callosum).

Say–Neger syndrome is a rare X-linked genetic disorder that is mostly characterized as developmental delay. It is one of the rare causes of short stature. It is closely related with trigonocephaly (a misshapen forehead due to premature fusion of bones in the skull). People with Say–Meyer syndrome have impaired growth, deficits in motor skills development and mental state.

It is suggested that it is from a X-linked transmission.

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.

People with Aarskog-Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Other abnormalities in people with Aarskog-Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).

Most males with Aarskog-Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia).

The intellectual development of people with Aarskog-Scott syndrome varies widely. Some may have mild learning and behavior problems, while others have normal intelligence. In rare cases, severe intellectual disability has been reported.

Aneuploidy is often fatal, but in this case there is "X-inactivation" where the effect of the additional gene dosage due to the presence of extra X chromosomes is greatly reduced.

Much like Down syndrome, the mental effects of 49,XXXXY syndrome vary. Impaired speech and behavioral problems are typical. Those with 49,XXXXY syndrome tend to exhibit infantile secondary sex characteristics with sterility in adulthood and have some skeletal anomalies. Skeletal anomalies include:

- Genu valgum

- Pes cavus

- Fifth finger clinodactyly

The effects also include:

- Cleft palate

- Club feet

- Respiratory conditions

- Short or/and broad neck

- Low birth weight

- Hyperextensible joints

- Short stature

- Narrow shoulders

- Coarse features in older age

- Hypertelorism

- Epicanthal folds

- Prognathism

- Gynecomastia (rare)

- Muscular hypotonia

- Hypoplastic genitalia

- Cryptorchidism

- Congenital heart defects

- A very round face in infancy

Most children with Allan–Herndon–Dudley syndrome have weak muscle tone (hypotonia) and underdevelopment of many muscles (muscle hypoplasia). As they get older, they usually develop joint deformities called contractures, which restrict the movement of certain joints. Abnormal muscle stiffness (spasticity), muscle weakness, and involuntary movements of the arms and legs also limit mobility. As a result, many people with Allan–Herndon–Dudley syndrome are unable to walk independently and become wheelchair-bound by adulthood.

Weaver syndrome (also called Weaver-Smith syndrome) is an extremely rare congenital disorder associated with rapid growth beginning in the prenatal period and continuing through the toddler and youth years. It is characterized by advanced osseous maturation, and distinctive craniofacial, skeletal, and neurological abnormalities. It was first described by Dr. David Weaver in 1974. It is similar to Sotos syndrome.

This syndrome is characterized by overgrowth and advanced bone age. Affected individuals are dysmorphic, with macrodolichocephaly, downslanting palpebral fissures and a pointed chin. The facial appearance is most notable in early childhood. Affected infants and children tend to grow quickly; they are significantly taller than their siblings and peers, and have an unusually large skull and large head. Adult height is usually in the normal range, although Broc Brown has the condition and was named the world's tallest teenager. As of late 2016, he was 7'8" and still growing.

Individuals with Sotos syndrome often have intellectual impairment, and most also have behavioral problems. Frequent behavioral impairments include attention deficit hyperactivity disorder (ADHD), phobias, obsessive compulsive disorder, tantrums, and impulsive behaviors (impulse control disorder). Problems with speech and language are also common. Affected individuals may often have stuttering, difficulty with sound production, or a monotone voice. Additionally, weak muscle tone (hypotonia) may delay other aspects of early development, particularly motor skills such as sitting and crawling.

Other signs include scoliosis, seizures, heart or kidney defects, hearing loss, and problems with vision. Some infants with this disorder experience jaundice and poor feeding. A small number of patients with Sotos syndrome have developed cancer, most often in childhood, but no single form of cancer has been associated with this condition. It remains uncertain whether Sotos syndrome increases the risk of specific types of cancer. If persons with this disorder have any increased cancer risk, their risk is only slightly greater than that of the general population.

Disorders considered in origin include:

1. Intellectual disability (ID) or intellectual and developmental disability (IDD), previously called mental retardation

2. Autism spectrum disorders, such as Asperger's syndrome or Kanner syndrome

3. Motor disorders including developmental coordination disorder and stereotypic movement disorder Tic disorders including Tourette's syndrome

4. Traumatic brain injury (including congenital injuries such as those that cause cerebral palsy)

5. Communication, speech and language disorders

6. genetic disorders, such as fragile-X syndrome, Down syndrome, attention deficit hyperactivity disorder, schizophrenia, schizotypal disorder, hypogonadotropic hypogonadal syndromes

7. disorders due to neurotoxicants like fetal alcohol spectrum disorder, Minamata disease caused by mercury, behavioral disorders including conduct disorder etc caused by other heavy metals, such as lead, chromium, platinum etc, hydrocarbons like dioxin, PBDEs and PCBs, medications and illegal drugs, like cocaine and others.

Rubinstein–Taybi syndrome (RTS), also known as broad thumb-hallux syndrome or Rubinstein syndrome, is a condition characterized by short stature, moderate to severe learning difficulties, distinctive facial features, and broad thumbs and first toes. Other features of the disorder vary among affected individuals.

People with this condition have an increased risk of developing noncancerous and cancerous tumors, leukemia, and lymphoma. This condition is sometimes inherited as an autosomal dominant pattern and is uncommon, many times it occurs as a de novo (not inherited) occurrence, it occurs in an estimated 1 in 125,000-300,000 births.

A case was described in 1957 by Michail, Matsoukas and Theodorou. In 1963, Jack Herbert Rubinstein (1925–2006) and Hooshang Taybi (1919–2006) described a larger series of cases.

Typical features of the disorder include:

- Broad thumbs and broad first toes and clinodactyly of the 5th finger

- Mental disability

- Small height, low bone growth, small head

- Cryptorchidism in males

- Unusual facies involving the eyes, nose, and palate

- Anesthesia may be dangerous in these patients: "According to the medical literature, in some cases, individuals with Rubinstein–Taybi syndrome may have complications (e.g., respiratory distress and/or irregular heart beats [cardiac arrythmias]) associated with a certain muscle relaxant (succinylcholine) and certain anesthesia. Any situations requiring the administration of anesthesia or succinylcholine (e.g., surgical procedures) should be closely monitored by skilled professionals (Anesthesiologists)." Primary literature suggests the children may have a higher rate of cardiac physical and conduction abnormalities which may cause unexpected results with cardioactive medications. A further editorial reply in the British Journal of Anaesthesia discusses changes in the face and airway structure making it more difficult to secure the airway under anaesthesia, however, complications appeared in a minority of cases, and routine methods of airway control in the operating room appears to be successful. They recommended close individual evaluation of Rubinstein–Taybi patients for anaesthetic plans.

A 2009 study found that children with RTS were more likely to be overweight and to have a short attention span, motor stereotypies, and poor coordination, and hypothesized that the identified CREBBP gene impaired motor skills learning. Other research has shown a link with long-term memory (LTM) deficit. See also Epigenetics in learning and memory.

Genitopatellar syndrome is a rare disorder with characteristic craniofacial features, congenital flexion contractures of the lower limbs, absent or abnormal patellae, urogenital anomalies, and severe psychomotor retardation.

In 2012, it was shown that mutations in the gene KAT6B cause the syndrome.

GMS syndrome is a syndrome characterised by goniodysgenesis, intellectual disability, and short stature.

Psychopathology and related behavioral abnormalities are typically seen in LFS, and they may be considered in the diagnosis of the disorder. The most common of these in LFS is an autism-like spectrum disorder, and LFS is considered as one of a number of genetic disorders associated with autism. Additional alterations of psychopathology with behavioral manifestations that have been observed in LFS include: psychotic behavior, schizophrenia, hyperactivity and attention-deficit hyperactivity disorder, aggression, oppositional defiant disorder, obsessive compulsive disorder, extreme shyness, learning disability, cognitive impairment, short-term memory deficit, low frustration tolerance, social dysfunction, lack of impulse control, eating disorder and associated malnutrition, attributed to psychogenic loss of appetite; and pyromania.

While psychiatric conditions like these are to be expected with LFS, there have also been cases of the disorder with some preservation of mental and behavioral abilities, such as problem solving, reasoning and normal intelligence.

The psychopathology of LFS usually exhibits schizophrenia. When schizophrenia is diagnosed in an individual known to be affected by intellectual disability, LFS may be considered in the differential diagnosis of schizophrenia, with confirmation of cause through appropriate psychiatric and genetic evaluation methods.

Neurodevelopmental disorder is a mental disorder. A narrower use of the term refers to a disorder of brain function which affects emotion, learning ability, self-control and memory and which unfolds as the individual grows.

LFS is clinically distinguished from other X-linked forms of intellectual disability by the accompanying presence of marfanoid habitus. Marfanoid habitus describes a group of physical features common to Marfan syndrome. Including Marfan syndrome and LFS, marfanoid features of this type have also been observed with several other disorders, one of which is multiple endocrine neoplasia type 2.

In LFS, specific features identified as marfanoid include: a long, narrow face; tall, thin stature; long, slender limbs, fingers and toes (not unlike arachnodactyly) with joint hyperextensibility, shortened halluces (the big toes) and long second toes.

The diagnosis of marfanoid habitus in LFS is often delayed because many of the physical features and characteristics associated with it are usually not evident until adolescence.

Tetrasomy 18p causes a wide range of medical and developmental problems.

Smith–Fineman–Myers syndrome (SFMS1), congenital disorder that causes birth defects. This syndrome was named after 3 men, Richard D. Smith, Robert M. Fineman and Gart G. Myers who discovered it around 1980.