The term "multisystem developmental disorder" has also been used to describe various developmental disorders. These include:

- Alagille syndrome, an autosomal dominant disorder with a wide range of features and manifestations. Its five most significant features are chronic cholestasis, a condition where bile cannot flow from the liver to the duodenum, occurring in 95% of cases; heart abnormalities (over 90%); butterfly vertebrae; posterior embryotoxon and a distinctive face (prominent forehead, deep-set eyes, and a pointed chin).

- Rubinstein-Taybi syndrome, a mental retardation syndrome characterized by broad thumbs, facial abnormalities, and big toes alongside mental retardation.

- Williams syndrome, a neurodevelopmental disorder characterized by a unique profile of strengths and deficits; most with the condition have mild mental retardation but have grammatical and lexical abilities above what would be expected from their IQs. They are hypersocial and empathetic, but social isolation is commonly experienced.

- Proteus syndrome, a congenital disorder causing disproportionate growth of skin, bone, and other tissues.

- Asphyxiating thoracic dysplasia, a autosomal recessive skeletal disorder with an estimated prevalence of between 1 in 100,000 and 1 in 130,000 live births.

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.

Neurodevelopmental disorders are impairments of the growth and development of the brain or central nervous system. A narrower use of the term refers to a disorder of brain function that affects emotion, learning ability, self-control and memory and that unfolds as an individual develops and grows.

The term is sometimes erroneously used as an exclusive synonym for autism spectrum disorders.

Multisystem developmental disorder (MSDD) is a term used by Stanley Greenspan to describe children under age 3 who exhibit signs of impaired communication as in autism, but with strong emotional attachments atypical of autism. It is described in the DC:0-3R manual as an optional diagnosis for children under two years of age.

Micro syndrome can be identified in people several ways, one of the most common is ocular problems or other physical traits that don't appear natural. It is especially easy to identify micro syndrome in infants and in younger children. Intellectual or developmental disabilities can seriously affect a patient in the way they think and move. So far according to studies all patients have had serious intellectual or developmental disabilities, and hypotonia is found in all the patients during infancy.

Overactive disorder associated with mental retardation and stereotyped movements is a pervasive developmental disorder (PDD) listed in Chapter V(F) of the tenth revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10); its diagnostic code is F84.4.

The tenth revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) has four categories of specific developmental disorder: specific developmental disorders of speech and language, specific developmental disorders of scholastic skills, specific developmental disorder of motor function, and mixed specific developmental disorder.

Micro syndrome also known as WARBM, and Warburg–Sjo–Fledelius syndrome, is a rare autosomal recessive genetic disorder characterized by microcephaly, microcornea, congenital cataract, intellectual or developmental disability, optic atrophy, and hypogenitalism.

In the third edition of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-III), SDD was opposed to the pervasive developmental disorders (PDD). There were two factors that were considered:

- The specificity of the impairment: in SDD there is one single domain that is affected, whereas in PDD multiple areas of functioning are affected.

- The nature of the impairment: development in SDD is delayed but not otherwise abnormal, whereas in PDD there are behavioral deviations that are not typical for any developmental stage.

In the fourth edition of the DSM specific developmental disorders are no longer grouped together. Instead they are reclassified as communication disorders, learning disorders, and motor skills disorders.

The earliest signs and symptoms occur in newborns and consist of hypotonia, but show up in youth as developmental delays, low muscle tone, learning disabilities, being overweight, autism-like symptoms, seizures, eczema, asthma, chest and ear infections, and abnormalities in face, hands, and feet. Autism-like symptoms consist of odd obsessions, repetitive behavior, poor use of eye contact, impaired speech, poor understanding of others’ emotions, idiosyncratic use of words or phrases. People with this disorder also tend to have a characteristic appearance, including prominent forehead, thin, highly arched eyebrows, depressed nasal bridge, full cheeks, deficient nasal alae and prominent columella, thin upper lip, and various minor anomalies of the pinnae. Heart, brain, gastrointestinal, and kidney problems such as Wilms tumor, hernias, spinal curvatures, Osteopenia, hearing and sight difficulties can also occur.

It has been associated with Wilms' tumor and brachydactyly.

This is an ill-defined disorder of uncertain nosological validity. The category is included here because of the evidence that children with moderate to severe intellectual disability (IQ below 35) who exhibit major problems in hyperactivity and inattention frequently show stereotyped behaviours; such children tend not to benefit from stimulant drugs (unlike those with an IQ in the normal range) and may exhibit a severe dysphoric reaction (sometimes with psychomotor retardation) when given stimulants; in adolescence the overactivity tends to be replaced by underactivity (a pattern that is not usual in hyperkinetic children with normal intelligence). It is also common for the syndrome to be associated with a variety of developmental delays, either specific or global. The extent to which the behavioural pattern is a function of low IQ or of organic brain damage is not known, neither is it clear whether the disorders in children with mild intellectual disability who show the hyperkinetic syndrome would be better classified here or under F90.- (Hyperkinetic disorders); at present they are included in F90-.

Diagnostic guidelines

Diagnosis depends on the combination of developmentally inappropriate severe overactivity, motor stereotypies, and moderate to severe intellectual disability; all three must be present for the diagnosis. If the diagnostic criteria for F84.0 (childhood autism), F84.1 (atypical autism) or F84.2 (Rett's syndrome) are met, that condition should be diagnosed instead.

Developmental disorders comprise a group of psychiatric conditions originating in childhood that involve serious impairment in different areas. There are several ways of using this term. The most narrow concept is used in the category "Specific Disorders of Psychological Development" in the ICD-10. These disorders comprise language disorders, learning disorders, motor disorders and autism spectrum disorders. In broader definitions ADHD is included, and the term used is neurodevelopmental disorders. Yet others include antisocial behavior and schizophrenia that begins in childhood and continues through life. However, these two latter conditions are not as stable as the other developmental disorders, and there is not the same evidence of a shared genetic liability.

Developmental disorders are present from early life. They usually improve as the child grows older, but they also entail impairments that continue through adult life. There is a strong genetic component, and more males are afflicted than females.

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.

It is common for individuals with PDD-NOS to have more intact social skills and a lower level of intellectual deficit than individuals with other PDDs. Characteristics of many individuals with PDD-NOS are:

- Communication difficulties (e.g., using and understanding language)

- Difficulty with social behavior

- Difficulty with changes in routines or environments

- Uneven skill development (strengths in some areas and delays in others)

- Unusual play with toys and other objects

- Repetitive body movements or behavior patterns

- Preoccupation with fantasy, such as imaginary friends in childhood

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

Learning disabilities are diagnosed when the children are young and just beginning school. Most learning disabilities are found under the age of 9.

Young children with communication disorders may not speak at all, or may have a limited vocabulary for their age. Some children with communication disorders have difficulty understanding simple directions or are unable to name objects. Most children with communication disorders are able to speak by the time they enter school, however, they continue to have problems with communication. School-aged children often have problems understanding and formulating words. Teens may have more difficulty with understanding or expressing abstract ideas.

Mental retardation is coded on Axis II of the DSM-IV-TR. The diagnostic criteria necessary in order to diagnose intellectual disability consists of:

There are varying degrees of intellectual disability, which are identified by an IQ test.

Mental retardation, Severity Unspecified: This unspecified diagnosis is given when there is a strong assumption that the child is mentally retarded, but cannot be tested because the individual is too impaired, not willing to take the IQ test or is an infant.

Symptoms of PDD may include behavioral and communication problems such as:

- Difficulty using and understanding language.

- Difficulty relating to people, objects, and events; for example, lack of eye contact, pointing behavior, and lack of facial responses.

- Unusual play with toys and other objects.

- Difficulty with changes in routine or familiar surroundings.

- Repetitive body movements or behavior patterns, such as hand flapping, hair twirling, foot tapping, or more complex movements.

- Inability to cuddle or be comforted.

- Difficulty regulating behaviors and emotions, which may result in temper tantrums, anxiety, and aggression.

- Emotional breakdowns.

Children with PDD vary widely in abilities, intelligence, and behaviors. Some children do not speak at all, others speak in limited phrases or conversations, and some have relatively normal language development. Repetitive play skills and limited social skills are generally evident as well. Unusual responses to sensory information – loud noises, lights – they also are common.

Most of the signs of MWS are present during the neonatal period. The most common signs at this state are multiple congenital joint contractures, dysmorphic features with mask-like face, blepharophimosis, ptosis, micrognathia, cleft or high arched palate, low-set ears, arachnodactyly, chest deformation as pectus, kyphoscoliosis and absent deep tendon reflexes are frequent minor malformations have also been described and consist of renal anomalies, cardiovascular abnormalities, hypospadias, omphalomesenteric duct, hypertriphic pyloric stenosis, duodenal bands, hyoplastic right lower lobe of the lung, displacement of the larynx to the right and vertebral abnormalities, cerebral malformations.

- 75% of children with MWS have blepharophimosis, small mouth, micrognathia, kyphosis/scoliosis, radio ulnar synostose and multiple contractures.

- They have severe developmental delay; congenital joint contractures and blepharophimosis should be present in every patient

- 2 out of 3 of the following signs should be manifested: post natal growth, mask-like faces, retardation, and decreased muscular mass.

- Some may require additional signs such as; micrognathia, high arched or cleft palate, low set ears, kyphoscoliosis.

- The symptoms of MWS are normally diagnosed during the newborn period

Separation anxiety disorder

- excessive stress when separated from home or family

- fear of being alone

- refusal to sleep alone

- clinginess

- excessive worry about safety

- excessive worry about getting lost

- frequent medical complaints with no cause

- refusal to go to school

Selective mutism

- unable to speak in certain social situations, even though they are comfortable speaking at home or with friends

- difficulty maintaining eye contact

- may have blank facial expressions

- stiff body movements

- may have a worrisome personality

- may be incredibly sensitive to sound

- difficulty with verbal and non-verbal expression

- may appear shy, when in reality, they have a fear of people.

Reactive attachment disorder of infancy or early childhood

- withdrawing from others

- aggressive attitude towards peers

- awkwardness or discomfort

- watching others but not engaging in social interaction

Stereotypic movement disorder

- head banging

- nail biting

- hitting or biting oneself

- hand waving or shaking

- rocking back and forth

The natural history of MWS is not well known: many patients died in infancy and clinical follow-up has been reported in few surviving adults. However, diagnosis may be more difficult to establish in adults patients, such as: blepharophimosis, contractures, growth retardation, and developmental delay, whereas minor face anomalies are less noticeable as the patient grows older. Throughout the development of the patient from young child to older adult changes the behavior drastically, from kindness to restless and hyperactive to aggressive.

Most of the signs and symptoms of the Joubert syndrome appear very early in infancy with most children showing delays in gross motor milestones. Although other signs and symptoms vary widely from individual to individual, they generally fall under the hallmark of cerebellum involvement or in this case, lack thereof. Consequently, the most common features include ataxia (lack of muscle control), hyperpnea (abnormal breathing patterns), sleep apnea, abnormal eye and tongue movements, and hypotonia in early childhood. Other malformations such as polydactyly (extra fingers and toes), cleft lip or palate, tongue abnormalities, and seizures may also occur. Developmental delays, including cognitive, are always present to some degree.

Those suffering from this syndrome often exhibit specific facial features such as a broad forehead, arched eyebrows, ptosis (droopy eyelids), hypertelorism (widely spaced eyes), low-set ears and a triangle shaped mouth. Additionally, this disease can include a broad range of other abnormalities to other organ systems such as retinal dystrophy, kidney diseases, liver diseases, skeletal deformities and endocrine (hormonal) problems.

Features of YVS include growth retardation before and after birth, defective growth of the bones of the skull along with complete or partial absence of the shoulder blades and characteristic facial features. Additional symptoms may include abnormalities of the fingers and/or toes. In most cases, infants with this disorder experience severe feeding problems and respiratory difficulties. In addition, affected infants may have heart defects.

Studies suggest that persons with PDD-NOS belong to one of three very different subgroups:

- A high-functioning group (around 25 percent) whose symptoms largely overlap with that of Asperger syndrome, but who differ in terms of having a lag in language development and/or mild cognitive impairment. (The criteria for Asperger syndrome excludes a speech delay or a cognitive impairment.)

- A group (around 25 percent) whose symptoms more closely resemble those of autism spectrum disorder, but do not fully meet all its diagnostic signs and symptoms.

- The biggest group (around 50 percent) consists of those who meet all the diagnostic criteria for autism spectrum disorder, but whose stereotypical and repetitive behaviors are noticeably mild.