Acromicric dysplasia

Alternate names

Acromicric skeletal dysplasia

Definition

Acromicric dysplasia is a condition characterized by severely short stature, short limbs, stiff joints, and distinctive facial features.

Epidemiology

Acromicric dysplasia is a rare disorder; its prevalence is unknown.

Cause

• Acromicric dysplasia is caused by mutations in the FBN1 gene, which provides instructions for making a large protein called fibrillin-1.
• This protein is transported out of cells into the extracellular matrix, which is an intricate lattice of proteins and other molecules that forms in the spaces between cells.
• In this matrix, molecules of fibrillin-1 attach (bind) to each other and to other proteins to form threadlike filaments called microfibrils.
• The microfibrils become part of the fibers that provide strength and flexibility to connective tissues, which support the bones, skin, and other tissues and organs.
• Additionally, microfibrils store molecules called growth factors, including transforming growth factor beta (TGF-β), and release them at various times to control the growth and repair of tissues and organs throughout the body.

Gene mutations

• Most of the FBN1 gene mutations that cause acromicric dysplasia change single protein building blocks in the fibrillin-1 protein.
• The mutations result in a reduction and disorganization of the microfibrils.
• Without enough normal microfibrils to store TGF-β, the growth factor is abnormally active.
• These effects likely contribute to the physical abnormalities that occur in acromicric dysplasia, but the mechanisms are unclear.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

Acromicric dysplasia is an autosomal dominant condition, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Most cases result from new mutations in the gene and occur in people with no history of the disorder in their family. In other cases, an affected person inherits the mutation from one affected parent.

Signs and symptoms

The following list includes the most common signs and symptoms in people with acromicric dysplasia. These features may be different from person to person. Some people may have more symptoms than others, and they can range from mild to severe. This list does not include every symptom that has been described in the condition.

Symptoms of acromicric dysplasia may include:

• Growth delay and short stature
• Short bones in the hands and feet
• Distinctive facial features
• Joint limitations that get worse over time
• Acromicric dysplasia is present from birth.
• Growth delay occurs in the first year of life.
• Over time, people with acromicric dysplasia may develop hip problems (hip dysplasia) and carpal tunnel syndrome.

Other symptoms may include frequent ear infections, hoarse voice, lung diseases like asthma, and eye abnormalities.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abnormal eyebrow morphology(Abnormality of the eyebrow)
• Anteverted nares(Nasal tip, upturned)
• Brachydactyly(Short fingers or toes)
• Long eyelashes(Increased length of eyelashes)
• Long philtrum
• Round face(Circular face)
• Severe short stature(Dwarfism)
• Short nose(Decreased length of nose)
• Short palm
• Small hand(Disproportionately small hands)

30%-79% of people have these symptoms

• Bulbous nose
• Decreased nerve conduction velocity
• Narrow mouth(Small mouth)
• Thick lower lip vermilion(Increased volume of lower lip)

5%-29% of people have these symptoms

• Abnormality of epiphysis morphology(Abnormal shape of end part of bone)
• Abnormality of femur morphology(Abnormality of the thighbone)
• Delayed skeletal maturation(Delayed bone maturation)
• Fifth metacarpal with ulnar notch
• Hoarse voice(Hoarseness)
• Joint stiffness(Stiff joint)
• Ovoid vertebral bodies
• Short metacarpal(Shortened long bone of hand)

Diagnosis

• Diagnosis of acromicric dysplasia is based on the symptoms, clinical exam, and imaging studies. The bones of people with acromicric dysplasia have characteristic findings seen on x-rays.
• The results of genetic testing can help confirm the diagnosis.

Treatment

Treatment of acromicric dysplasia is focused on managing the symptoms. Treatment may include physical therapy and surgery to correct hip problems.

NIH genetic and rare disease info

• NIH info on Acromicric dysplasia

Acromicric dysplasia is a rare disease.

Acromicric dysplasia Resources
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