A defining characteristic of dwarfism is an adult height less than the 2.3rd percentile of the CDC standard growth charts. There is a wide range of physical characteristics. Variations in individuals are identified by diagnosing and monitoring the underlying disorders. There may not be any complications outside adapting to their size.

Short stature is a common replacement of the term 'dwarfism', especially in a medical context. Short stature is clinically defined as a height within the lowest 2.3% of those in the general population. However, those with mild skeletal dysplasias may not be affected by dwarfism. In some cases of untreated hypochondroplasia, males grow up to 5 feet 5 inches. Although that is short in a relative context, it does not fall into the extreme ranges of the growth charts.

Disproportionate dwarfism is characterized by shortened limbs or a shortened torso. In achondroplasia one has an average-sized trunk with short limbs and a larger forehead. Facial features are often affected and individual body parts may have problems associated with them. Spinal stenosis, ear infection, and hydrocephalus are common. In case of spinal dysostosis, one has a small trunk, with average-sized limbs.

Proportionate dwarfism is marked by a short torso with short limbs, thus leading to a height that is significantly below average. There may be long periods without any significant growth. Sexual development is often delayed or impaired into adulthood. This dwarfism type is caused by an endocrine disorder and not a skeletal dysplasia.

Physical effects of malformed bones vary according to the specific disease. Many involve joint pain caused by abnormal bone alignment, or from nerve compression. Early degenerative joint disease, exaggerated lordosis or scoliosis, and constriction of spinal cord or nerve roots can cause pain and disability. Reduced thoracic size can restrict lung growth and reduce pulmonary function. Some forms of dwarfism are associated with disordered function of other organs, such as the brain or liver, sometimes severely enough to be more of an impairment than the unusual bone growth.

Mental effects also vary according to the specific underlying syndrome. In most cases of skeletal dysplasia, such as achondroplasia, mental function is not impaired. However, there are syndromes which can affect the cranial structure and growth of the brain, severely impairing mental capacity. Unless the brain is directly affected by the underlying disorder, there is little to no chance of mental impairment that can be attributed to dwarfism.

The psycho-social limitations of society may be more disabling than the physical symptoms, especially in childhood and adolescence, but people with dwarfism vary greatly in the degree to which social participation and emotional health are affected.

- Social prejudice against extreme shortness may reduce social and marital opportunities.

- Numerous studies have demonstrated reduced employment opportunities. Severe shortness is associated with lower income.

- Self-esteem may suffer and family relationships may be affected.

- Extreme shortness (in the low 2–3-foot [60–90 cm] range) can, if not accommodated for, interfere with activities of daily living, like driving or using countertops built for taller people. Other common attributes of dwarfism such as bowed knees and unusually short fingers can lead to back problems, and difficulty in walking and handling objects.

- Children with dwarfism are particularly vulnerable to teasing and ridicule from classmates. Because dwarfism is relatively uncommon, children may feel isolated from their peers.

Dwarfism can result from myriad medical conditions, each with its own separate symptoms and causes. Extreme shortness in humans with proportional body parts usually has a hormonal cause, such as growth-hormone deficiency, once called "pituitary dwarfism". Two disorders, achondroplasia and growth hormone deficiency, are responsible for the majority of human dwarfism cases.

Since primordial dwarfism disorders are extremely rare, misdiagnosis is common. Because children with PD do not grow like other children, poor nutrition, a metabolic disorder, or a digestive disorder may be diagnosed initially. The correct diagnosis of PD may not be made until the child is 5 years old and it becomes apparent that the child has severe dwarfism.

People with spondyloepiphyseal dysplasia are short-statured from birth, with a very short trunk and neck and shortened limbs. Their hands and feet, however, are usually average-sized. This type of dwarfism is characterized by a normal spinal column length relative to the femur bone. Adult height ranges from 0.9 meters (35 inches) to just over 1.4 meters (55 inches). Curvature of the spine (kyphoscoliosis and lordosis) progresses during childhood and can cause problems with breathing. Changes in the spinal bones (vertebrae) in the neck may also increase the risk of spinal cord damage. Other skeletal signs include flattened vertebrae (platyspondyly), a hip joint deformity in which the upper leg bones turn inward (coxa vara), and an inward- and downward-turning foot (called clubfoot). Decreased joint mobility and arthritis often develop early in life. Medical texts often state a mild and variable change to facial features, including cheekbones close to the nose appearing flattened, although this appears to be unfounded. Some infants are born with an opening in the roof of the mouth, which is called a cleft palate. Severe nearsightedness (high myopia) is sometimes present, as are other eye problems that can affect vision such as detached retinas. About one-quarter of people with this condition have mild to moderate hearing loss.

Achondroplasia is a genetic disorder that results in dwarfism. The arms and legs are short, while the trunk is typically of normal length. Those affected have an average adult height of for males and for females. Other features include an enlarged head and prominent forehead. Intelligence is generally normal.

Achondroplasia is due to a mutation in the FGFR3 gene. In about 80% of cases this occurs as a new mutation during early development. In the other cases it is inherited from one's parents in an autosomal dominant manner. Those with two effected genes do not typically survive. Diagnosis is generally based on symptoms, but may be supported by genetic testing if uncertain.

Treatments may include support groups and growth hormone therapy. Efforts to treat or prevent complications such as obesity, hydrocephalus, obstructive sleep apnea, middle ear infections, or spinal stenosis may be required. Life expectancy of those affected is about 10 years less than average. The condition affects about 1 in 27,500 people. Rates are higher in Denmark and Latin America. The shortest known adults with the condition is Jyoti Amge at .

Achondroplasia can be detected before birth by prenatal ultrasound. A DNA test can be performed before birth to detect homozygosity, wherein two copies of the mutant gene are inherited, a lethal condition leading to stillbirths. Clinical features include megalocephaly, short limbs, prominent forehead, thoracolumbar kyphosis and mid-face hypoplasia. Complications like dental malocclusion, hydrocephalus and repeated otitis media can be observed. The risk of death in infancy is increased due to the likelihood of compression of the spinal cord with or without upper airway obstruction.

Primordial dwarfism is a form of dwarfism that results in a smaller body size in all stages of life beginning from before birth. More specifically, primordial dwarfism is a diagnostic category including specific types of profoundly proportionate dwarfism, in which individuals are extremely small for their age, even as a fetus. Most individuals with primordial dwarfism are not diagnosed until they are about 3-5 years of age.

Medical professionals typically diagnose the fetus as being small for the gestational age, or as having intrauterine growth disability when an ultrasound is conducted. Typically, people with primordial dwarfism are born with very low birth weights. After birth, growth continues at a much slower rate, leaving individuals with primordial dwarfism perpetually years behind their peers in stature and in weight.

Most cases of short stature are caused by skeletal or endocrine disorders. The five subtypes of primordial dwarfism are among the most severe forms of the 200 types of dwarfism, and some sources estimate that there are only 100 individuals in the world with the disorder. Other sources list the number of people

currently afflicted as high as 100 in North America.

It is rare for individuals affected by primordial dwarfism to live past the age of 30. In the case of microcephalic osteodysplastic primordial dwarfism type 2 (MOPDII) there can be increased risk of vascular problems, which may cause premature death.

Prenatal and neonatal diagnosis of boomerang dysplasia includes several prominent features found in other osteochondrodysplasias, though the "boomerang" malformation seen in the long bones is the delineating factor.

Featured symptoms of boomerang dysplasia include: dwarfism (a lethal type of infantile dwarfism caused by systemic bone deformities), underossification (lack of bone formation) in the limbs, spine and ilium (pelvis); proliferation of multinucleated giant-cell chondrocytes (cells that produce cartilage and play a role in skeletal development - chondrocytes of this type are rarely found in osteochondrodysplasias), brachydactyly (shortened fingers) and (undersized, shortened bones).

The characteristic "boomerang" malformation presents intermittently among random absences of long bones throughout the skeleton, in affected individuals. For example, one individual may have an absent radius and fibula, with the "boomerang" formation found in both ulnas and tibias. Another patient may present "boomerang" femora, and an absent tibia.

Fibrochondrogenesis is a congenital disorder presenting several features and radiological findings, some which distinguish it from other osteochondrodysplasias. These include: fibroblastic dysplasia and fibrosis of chondrocytes (cells which form cartilage); and flared, widened

long bone metaphyses (the portion of bone that grows during childhood).

Other prominent features include dwarfism, shortened ribs that have a appearance, micrognathism (severely underdeveloped jaw), macrocephaly (enlarged head), thoracic hypoplasia (underdeveloped chest), enlarged stomach, platyspondyly (flattened spine), and the somewhat uncommon deformity of tongue (in which the tongue appears split, resembling that of a reptile).

Because collagen plays an important role in the development of the body, people with Kniest Dysplasia will typically have their first symptoms at birth. These symptoms can include:.

- Musculoskeletal Problems

- Short limbs

- Shortened body trunk

- Flattened bones in the spine

- kyphoscoliosis

- Scoliosis (Lateral curvature of the spine)

- Early development of arthritis

- Respiratory problems

- Respiratory tract infection

- Difficulty breathing

- Eye problems

- Severe myopia (near-sightedness)

- Cataract (cloudiness in the lens of the eye)

- Hearing problems

- progressive hearing loss

- ear infections

Most symptoms are chronic and will continue to worsen as the individual ages. It is essential to have regular checkups with general doctors, orthopedist, ophthalmologists, and/or otorhinolaryngologists. This will help to detect whether there are any changes that could cause concern.

Spondyloepiphyseal dysplasia congenita (abbreviated to SED more often than SDC) is a rare disorder of bone growth that results in dwarfism, characteristic skeletal abnormalities, and occasionally problems with vision and hearing. The name of the condition indicates that it affects the bones of the spine (spondylo-) and the ends of bones (epiphyses), and that it is present from birth (congenital). The signs and symptoms of spondyloepiphyseal dysplasia congenita are similar to, but milder than, the related skeletal disorders achondrogenesis type 2 and hypochondrogenesis. Spondyloepiphyseal dysplasia congenita is a subtype of collagenopathy, types II and XI.

The cause of platyspondyly in fibrochondrogenesis can be attributed in part to odd malformations and structural flaws found in the vertebral bodies of the spinal column in affected infants.

Fibrochondrogenesis alters the normal function of chondrocytes, fibroblasts, metaphyseal cells and others associated with cartilage, bone and connective tissues. Overwhelming

disorganization of cellular processes involved in the formation of cartilage and bone (ossification), in combination with fibroblastic degeneration of these cells, developmental errors and systemic skeletal malformations describes the severity of this lethal osteochondrodysplasia.

Boomerang dysplasia is a lethal form of osteochondrodysplasia known for a characteristic congenital feature in which bones of the arms and legs are malformed into the shape of a boomerang. Death usually occurs in early infancy due to complications arising from overwhelming systemic bone malformations.

Osteochondrodysplasias are skeletal disorders that cause malformations of both bone and cartilage.

Kniest Dysplasia is a rare form of dwarfism caused by a mutation in the COL2A1 gene on chromosome 12. The COL2A1 gene is responsible for producing type II collagen. The mutation of COL2A1 gene leads to abnormal skeletal growth and problems with hearing and vision. What characterizes kniest dysplasia from other type II Osteochondrodysplasia is the level of severity and the dumb-bell shape of shortened long tubular bones. This condition was first diagnosed by Dr. Wilhelm Kniest in 1952. Dr. Kniest noticed that his 50 year old patient was having difficulties with restricted joint mobility. The patient had a short stature and was also suffering from blindness. Upon analysis of the patient's DNA, Dr. Kniest discovered that a mutation had occurred at a splice site of the COL2A1 gene. This condition is very rare and occurs less than 1 in 1,000,000 people. Males and females have equal chances of having this condition. Currently, there is no cure for kniest dysplasia. Alternative names for Kniest Dysplasia can include Kniest Syndrome, Swiss Cheese Cartilage Syndrome, Kniest Chondrodystrophy, or Metatrophic Dwarfism Type II.

Insular dwarfism, a form of phyletic dwarfism, is the process and condition of the reduction in size of large animals over a number of generations when their population's range is limited to a small environment, primarily islands. This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing. This process has occurred many times throughout evolutionary history, with examples including dinosaurs, like "Europasaurus", and modern animals such as elephants and their relatives. This process, and other "island genetics" artifacts, can occur not only on traditional islands, but also in other situations where an ecosystem is isolated from external resources and breeding. This can include caves, desert oases, isolated valleys and isolated mountains ("sky islands"). Insular dwarfism is one aspect of the more general "island rule", which posits that when mainland animals colonize islands, small species tend to evolve larger bodies, and large species tend to evolve smaller bodies.

Individuals affected by this disorder appear normal at birth. As the infant grows, however, their arms and legs do not develop properly and their body becomes thicker and shorter than normal The following are characteristics consistent with this condition:

- Brachydactyly syndrome

- Short stature

- Micromelia

- Skeletal dysplasia

- Abnormality of femur

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.

Mesomelia refers to conditions in which the middle parts of limbs are disproportionately short. When applied to skeletal dysplasias, mesomelic dwarfism describes generalised shortening of the forearms and lower legs. This is in contrast to rhizomelic dwarfism in which the upper portions of limbs are short such as in achondroplasia.

Forms of mesomelic dwarfism currently described include:

- Langer mesomelic dysplasia

- Ellis–van Creveld syndrome

- Robinow syndrome

- Léri–Weill dyschondrosteosis

Acromicric dysplasia is an extremely rare inherited disorder characterized by abnormally short hands and feet, growth retardation and delayed bone maturation leading to short stature. Most cases have occurred randomly for no apparent reason (sporadically). However, autosomal dominant inheritance has not been ruled out.

According to the disease database, Acromicric dysplasia is synonymous with Geleophysic dysplasia

(or Geleophysic Dwarfism) and Focal mucopolysaccharidosis.

Parastremmatic dwarfism is apparent at birth, with affected infants usually being described as "stiff", or as "twisted dwarfs" when the skeletal deformities and appearance of dwarfism further present themselves. Skeletal deformities usually develop in the sixth to twelfth month of an infant's life. The deformities may be attributed to osteomalacia, a lack of bone mineralization.

Hypochondroplasia (HCH) is a developmental disorder caused by an autosomal dominant genetic defect in the fibroblast growth factor receptor 3 gene ("FGFR3") that results in a disproportionately short stature, micromelia, and a head that appears large in comparison with the underdeveloped portions of the body, it is classified as short-limbed dwarfism.

Usually symptoms of cerebellar hypoplasia can be seen immediately at birth in cats, but sometimes can take two months or so to become apparent in dogs. Cerebellar hypoplasia causes jerky movements, tremors and generally uncoordinated motion. The animal often falls down and has trouble walking. Tremors increase when the animal is excited and subside when at ease.

Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN), is a very rare genetic disorder. This disorder is one that affects bone growth and is characterized by skeletal, brain, and skin abnormalities. Those affected by the disorder are severely short in height and commonly possess shorter arms and legs. In addition, the bones of the legs are often bowed and the affected have smaller chests with shorter rib bones, along with curved collarbones. Other symptoms of the disorder include broad fingers and extra folds of skin on the arms and legs. Developmentally, many individuals who suffer from the disorder show a higher level in delays and disability. Seizures are also common due to structural abnormalities of the brain. Those affected may also suffer with apnea, the slowing or loss of breath for short periods of time.

Many of the features of SADDAN are similar to those seen in other skeletal disorders, specifically achondroplasia and thanatophoric dysplasia.

Achondroplasia is a form of short-limbed dwarfism. This type of dwarfism is caused by the inability of the cartilage of the skeleton to ossify and turn to bone. Acanthosis nigricans is a skin condition in which areas of the skin is of a dark and velvety discoloration, often seen in the body folds and creases such as the armpits, groin, and neck. Within those affected by SADDAN, acanthosis nigricans develops early on, usually in infancy or early childhood.

Symptoms include:

- intellectual disability (more than half of the patients have an IQ below 50)

- microcephaly

- sometimes pancytopenia (low blood counts)

- cryptorchidism

- low birth weight

- dislocations of pelvis and elbow

- unusually large eyes

- low ears

- small chin

Parastremmatic dwarfism is a rare bone disease that features severe dwarfism, thoracic kyphosis (a type of scoliosis that affects the upper back), a distortion and twisting of the limbs, contractures of the large joints, malformations of the vertebrae and pelvis, and incontinence. The disease was first reported in 1970 by Leonard Langer and associates; they used the term "parastremmatic" from the Greek "parastremma", or "distorted limbs", to describe it. On X-rays, the disease is distinguished by a "flocky" or lace-like appearance to the bones. The disease is congenital, which means it is apparent at birth. It is caused by a mutation in the "TRPV4" gene, located on chromosome 12 in humans. The disease is inherited in an autosomal dominant manner.