The Dwarf Don Sebastián de Morra, by Velázquez. In his portraits of the dwarfs of Spain's royal court, the artist preferred a serious tone that emphasized their human dignity.
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Dwarfism is a condition in which a person, animal or plant is much below the ordinary size of the species. When applied to people, it implies not just extreme shortness, but a degree of disproportion. Dwarfism is now rarely used as a medical term and is sometimes (but not always) considered impolite or pejorative. Today, the term little person tends to be preferred. According to the Little People of America the human definition of this term is stated as such "a medical or genetic condition that usually results in an adult height of 4'10" or shorter, among both men and women, although in some cases a person with a dwarfing condition may be slightly taller than that." more...

Dandy-Walker syndrome
Darier's disease
Demyelinating disease
Dengue fever
Dental fluorosis
Dentinogenesis imperfecta
Depersonalization disorder
Dermatitis herpetiformis
Dermatographic urticaria
Desmoplastic small round...
Diabetes insipidus
Diabetes mellitus
Diabetes, insulin dependent
Diabetic angiopathy
Diabetic nephropathy
Diabetic neuropathy
Diamond Blackfan disease
Diastrophic dysplasia
Dibasic aminoaciduria 2
DiGeorge syndrome
Dilated cardiomyopathy
Dissociative amnesia
Dissociative fugue
Dissociative identity...
Dk phocomelia syndrome
Double outlet right...
Downs Syndrome
Duane syndrome
Dubin-Johnson syndrome
Dubowitz syndrome
Duchenne muscular dystrophy
Dupuytren's contracture
Dyskeratosis congenita
Dysplastic nevus syndrome

Of the hundreds of causes of dwarfism in humans, most are genetic, and most involve single gene variations that affect the structure or metabolism of bone, cartilage, or connective tissue. This class of disorder is referred to by physicians as skeletal dysplasias. Chondrodystrophies, chondrodysplasias, osteochondrodystrophies are also used (fairly interchangeably) in the medical literature to refer to most of these conditions. In many of these conditions, the bones are the primary affected body part, and the person is otherwise healthy. In many others, the genetic difference affects other body systems, causing unusual features or other major problems. Achondroplasia is one of the most common and perhaps the most easily recognized skeletal dysplasia. It affects approximately 1 in 40,000 children, both males and females as it is due to a mutation of an autosomal gene.

Problems faced by people with these conditions

  • Social and employment opportunities are greatly reduced, regardless of anti-discrimination laws. Self-esteem and family relationships are often affected, although not necessarily if the person(s) involved are emotionally healthy.
  • Extreme shortness (in the low 2-3 foot range) can interfere with ordinary activities of daily living, like driving or even using countertops built for taller people.
  • Many can have problems produced by the abnormal bone structures. 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.
  • Many of the conditions are associated with disordered function of other organs, such as brain or liver (although this is rare). These problems can be more disabling than the abnormal bone growth.


Shortness is usually the concern that brings the child to medical attention. Dwarfism becomes suspected because of obvious physical features, because of an obviously affected parent, or because body measurements (arm span, upper to lower segment ratio) indicate disproportion. Bone x-rays are often the key to recognition of specific skeletal dysplasia. Most children with suspected skeletal dysplasias will be referred to a genetics clinic for diagnostic confirmation and genetic counselling. See for a list of American referral centers with special expertise in skeletal dysplasias. In the last decade, genetic tests for some of the specific disorders have become available.

Medical treatment

For many forms of dwarfism, the best medical treatment that can be offered is accurate diagnosis, prognosis, and genetic counseling information.


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New tool yields dwarfism gene … while an old way pinpoints another
From Science News, 10/1/94

It's been a good summer for little people. Scientists have now tracked down the genetic bases of two more skeletal abnormalities underlying short stature, information that can aid genetic testing and perhaps lead to the prevention of, or treatments for, dwarfism.

Most recently, a multidisciplinary U.S.-Finnish team used a new analytical technique called fine-structure linkage disequilibrium mapping to determine the cause of diastrophic dysplasia (DTD). DTD causes most of the dwarfism in Finland and is the third most common form in the United States. People who inherit two defective DTD genes develop twisted bones and arthritis, says Johanna Hastbacka of the Whitehead Institute for Biomedical Research in Cambridge, Mass.

Most of the 5 million Finns descended from a small group that 2,000 years ago settled what is now Finland. Thus, Hastbacka, Whitehead colleague Eric S. Lander, and Albert de la Chapelle of the University of Helsinki assumed that the defective DTD gene most likely arose from one person in that group.

The researchers first examined the genetic codes of affected members of 18 families with this disease and from that narrowed their search to an end of chromosome 5. They then analyzed the genetic material of 77 Finnish families having at least one member with a DTD gene, looking for ever smaller regions of that chromosome common to all these individuals. That common section represents the remains of the original ancestor's chromosome bearing this defective gene, Hastbacka says.

The DTD gene codes for a protein similar to ones already known to exist in rats and a fungus. Those proteins transport sulfate in and out of cells. Tissue taken from people with DTD does not take up enough sulfate, the group reports in the Sept. 23 CELL. Without sugar sulfate compounds, cells that make bone cannot lay down material that is both tough and resilient, she adds.

This summer, John J. Wasmuth of the University of California, Irvine, and his colleagues reported finding the gene that is defective in achondroplasia, the commonest genetic form of dwarfism in most parts of the world. That gene, called fgfr3, lies on one end of chromosome 4. Its protein product sits on the surfaces of cells and binds to specific growth factors, the group reported in the July 29 CELL. They found the gene quickly because they had first studied it as a possible candidate in Huntington's disease, Wasmuth says.

In achondroplasia, limbs are too short and the head is too large. A single amino acid change in the fgfr3 protein seems responsible, says Arnold Munnich of the Necker Institute at the Hospital for Sick Children in Paris. When he and his colleagues examined the DNA sequence of the fgfr3 gene in people with the growth disorder, they found that one nucleotide had been replaced by another. As a result, part of the protein that runs through a cell membrane contains an arginine amino acid where normally a glycine lies, Munnich and his colleagues report in the Sept. 15 NATURE. They found this amino acid switch in six unrelated individuals with achondroplasia in their heritage and in 17 sporadic cases -- in which parents spontaneously developed the genetic defect and passed it on to their children.

COPYRIGHT 1994 Science Service, Inc.
COPYRIGHT 2004 Gale Group

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