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Metatropic dysplasia
Sunday, 14 August 2005
Sunday, 14 August 2005
Metatrophic dysplasia; Metatropic dysplasia I; Metatropic dwarfism; Chondrodystrophy, Hyperplastic f

What

Metatropic dysplasia is a rare, inherited, genetic condition that is characterized by progressive dwarfism. Metatropic literally means “ever changing.” This is an appropriate description because early in life, affected individuals have a long torso with short arms and legs. As the child grows and develops, the torso will become shortened as the curvature of the spine becomes more pronounced.

Who

The true incidence of metatropic dysplasia is not known because it is so rare. There are less than 80 cases worldwide reported in the medical literature. There is also no known racial or gender preference.

Signs and Symptoms

Children born with metatropic dysplasia display different signs and symptoms over the course of childhood. Infants are generally born with disproportionately short arms and legs, a narrow chest, long fingers and toes, and often a short tail-like appendage, but with a normal head and face. After the age of about 6 months, these children develop rapidly progressing kyphoscoliosis, meaning that the spine curves abnormally both sideways (forming an “S” shape) and forwards (giving the child a hunchback-like appearance). As the kyphoscoliosis worsens, the lungs can be compressed, making breathing extremely difficult. Due to the abnormal curvature of the spine, these children will ultimately develop disproportionately short chests compared to the arms and legs. Joint problems such as early-onset arthritis can also occur. Untreated kyphoscoliosis is the primary concern in individuals with metatropic dysplasia, as it can lead not only to breathing problems but also to muscular weakness and compression of nerves in the spine.

Possible Causes

While this disorder clearly has a genetic component the exact nature of the defect or the mode of inheritance is not yet understood. There are three suspected subtypes: 1) a non-lethal type with autosomal recessive transmission (most common); 2) a non-lethal dominant type (less common); and 3) a lethal type with death before or shortly after birth, possibly with autosomal recessive inheritance. Autosomal recessive conditions require an affected individual to inherit two copies of the defective gene (one from each parent) while an autosomal dominant process requires only one copy to be inherited.

Diagnosis

The diagnosis is usually made based on identification of key features on X-ray evaluation performed soon after birth. These features include: vertebrae (bones of the spine) that are abnormally flat, exaggerated curvature of the spine, short arms and legs in relation to the rest of the body, abnormal hip bones of the hip, and the presence of a small tail-like appendage. It is believed that the disease could be diagnosed in the prenatal period by ultrasound due to these characteristic features, but no cases of prenatal diagnosis have been reported to this point. Unfortunately there is no confirmatory blood test as the genetic defect has not been identified.

Treatment

While there is no known cure for metatropic dysplasia, treatment should be focused on preventing the rapid development of kyphoscoliosis and the breathing problems that can be associated with it. For this reason, children with metatropic dysplasia are often fitted with a permanent surgical corset. Kyphoscoliosis can also be treated by surgically fusing the vertebrae. This surgery decreases the individual’s range of motion but minimizes the curvature of the spine. Sometimes, the top two vertebrae (the neck bones) are fused, as these bones are particularly unstable and may be injured if the child turns his/her head quickly or is jarred. Individuals with metatropic dysplasia are usually followed by various medical specialists – including an orthopedic surgeon (to follow the growth and development of the child’s bones), a rheumatologist (to take care of the child’s arthritis), and a neurosurgeon (to ensure that the child’s bones do not negatively affect his/her nerves). Consultation with a genetic counselor is also often recommended for future pregnancies.

Prognosis

With proper treatment, most individuals with metatropic dysplasia can live full, healthy lives. Due to their extreme spine curvature, most grow to be less than four feet tall and require several surgeries throughout life to limit the progression of their kyphoscoliosis. If the kyphoscoliosis is properly and pro-actively treated, many of the associated complications can be prevented. Children with metatropic dysplasia develop normally and have normal intelligence.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Metatropic Dysplasia Dwarf Registry
This is the homepage for a support group for those with metatropic dysplasia and their families. Included is extensive and easy-to-understand information about the disease, information on how to network with others affected by the disease, and contact information for organizations and physicians who specialize in metatropic dysplasia.

Little People of America (LPA) Online
A nonprofit organization that provides support and information to people of short stature and their families. Included are excellent resources on different types of dwarfism, medical information, instructions on how to join the LPA e-mail discussion group, and links to various other relevant websites.

Amersham Health
Simple explanation of major findings of this condition and some x-rays.

Human Growth Foundation
World-wide website focused on improving on growth disorders.

MAGIC Foundation for Children's Growth
Nice foundation focused on improving the lives of children with growth related disorders.

Greenberg Center for Skeletal Dysplasias
Nice website with many more links to related sites.

Google Search for Metatropic dysplasia

References and Sources

Genevieve D (2005). Long-term follow-up in a patient with metatropic dysplasia, American Journal of Medical Genetics, 135A, p 342-3. Sillence D and Kozloski K (2004). Metatropic dysplasia. www.orpha.net/data/patho/GB/uk-MetatropicDysplasia.pdf Emedicine.com: www.emedicine.com/ped/topic625.htm