What Is Acromicric Dysplasia?
Acromicric dysplasia is an extremely rare genetic condition that affects the growth and development of the bones. It is characterized by severely short stature, short extremities, distinctive facial features, and stiff joints. When the infants are born, they will appear normal; over time, the growth will be delayed, resulting in short stature. For adults with acromicric dysplasia, the average height is approximately four feet, two inches to four feet, six inches. The bones in the extremities, such as arms, legs, hands, and feet, are shorter than expected for a normal individual's height.
Other skeletal features in this disorder are abnormally shaped bones of the spine, slowed mineralization of bone, and less movement of the joints. Individuals with this disorder may develop carpal tunnel syndrome, which can lead to tingling, numbness, weakness in the hands and fingers, and hip dysplasia (misalignment of the hip joints). The distinct facial features of the syndrome may include a round face, a bulbous nose with upturned nostrils, sharply defined eyebrows, long eyelashes, a small mouth with thick lips, and a long space between the nose and upper lip. As the child ages and reaches adulthood, the facial features become less prominent.
This condition does not affect intelligence or cognitive skills. Acromicric dysplasia is caused by a mutation in the LTBP3 gene or the FBN1 gene and is inherited in an autosomal dominant pattern. Diagnosis is performed based on clinical exams, symptoms, and imaging studies. Finally, by performing genetic testing, this condition is confirmed. This condition generally has no complications, a good prognosis, and an average life expectancy.
What Is the Cause of Acromicric Dysplasia?
Acromicric dysplasia is caused by genetic mutations in the FBN1 (fibrillin-1) gene. This gene is essential in providing information for protein production, known as fibrillin-1. This protein moves out of cells into a space between cells called the extracellular matrix. In the extracellular matrix, fibrillin-1 molecules bind to one another and other proteins to create threadlike microfibrils.
These microfibers provide strength and flexibility to connective tissues that support the skin, bones, and other tissues and organs. Also, these microfibrils are essential for storing and releasing molecules called growth factors, like transforming growth factor beta (TGF-β). These molecules are released at various times to control the growth and repair of tissues and organs. The genetic variations of the gene FBN1 can change the protein fibrillin-1, which will disorganize and cause a reduction in microfibril. Without sufficient microfibrils to store the growth factor, abnormal activity of growth factors occurs, contributing to physical abnormalities. However, the exact mechanisms are unclear.
Acromicric dysplasia occurs in an autosomal dominant pattern, which means one copy of the defective gene in each cell is enough to cause this condition. However, most cases occur due to new mutations in the gene. This occurs in individuals with no family history of the disorder.
What Are the Symptoms of Acromicric Dysplasia?
Acromicric dysplasia is a rare condition; at birth, the child will appear normal, but as the child grows, the symptoms of acromicric dysplasia appear. The types of symptoms and their intensity may vary among affected individuals with this disease.
Some Common Symptoms Include:
Abnormally Short Hands and Feet - The main characteristic feature of this condition is abnormally short hands and feet. This is mainly due to delayed growth, which leads to short stature. Most affected individuals will be at an average height of four feet when they become adults.
Brachydactyly - This is a condition where the digits appear disproportionately short compared to the hand and foot. Brachydactyly describes a series of distinct shortened digit patterns. Certain bones in the hands and fingers, such as metacarpals and phalanges, and bones in the feet and toes, such as metatarsals and phalanges, are very short and stubby. Also, some bones in the middle of the hand may taper towards the end to form a sharp end, while bones in the toes may appear cone-shaped.
Hoarse Voice - A change in the quality or pitch of the voice, giving a husky and scratchy voice, is called a hoarse voice.
Joint Stiffness - Joint stiffness is a sensation of tightness in the joints when trying to move them after being inactive for a period. Joint stiffness typically subsides over time.
Abnormal Facial Features:
-
Eyebrows - The eyebrow morphology will be abnormally sharp and defined.
-
Anteverted Nostrils - The nose will appear in an upturned nose pattern.
-
Long Eyelashes - The eyelashes will be long, sharp, and well-defined.
-
Long Philtrum - The distance between the nasal base and upper lip vermilion border’s midline will be greater when compared to average individuals.
-
Round Face - The affected individual will have a more circular face than usual as viewed from the front.
-
Short Nose - The nose appears short due to the decreased length from the nasal root to the tip.
-
Bulbous Nose - The nose appears bulbous when there is increased volume and globular shape at the tip of the nose.
-
Narrow Mouth - The affected individuals have small mouths due to the decreased width of the oral aperture.
-
Thick Lower Vermilion - The lower lip will be longer, giving a prominent lower lip appearance.
How Is This Condition Diagnosed?
The diagnosis of acromicric dysplasia is based on a clinical examination that includes a complete medical history, family history, and clinical evaluation that identifies and checks the characteristic features of this condition. More laboratory tests may be conducted to confirm the diagnosis. The X-ray can help identify the abnormalities in the hands and feet. Also, abnormalities in the growth pattern can be identified when the cartilage cells are seen under the microscope.
What Is the Treatment for Acromicric Dysplasia?
There is no permanent cure for acromicric dysplasia, as it is a genetic disorder. However, treatment for this condition focuses on treating the signs and symptoms present in each individual. No major complications will appear in this condition, and the life expectancy is normal. So, the prognosis for affected individuals is also good.
Conclusion:
Acromicric dysplasia is a rare genetic disorder caused by FBN1 (fibrillin-1) gene variations. The affected individuals will appear short due to short hands and limbs. They also have distinct facial features with joint stiffness. Generally, the mental status of individuals is normal. There is no cure for this condition. However, treatment aims to ease symptoms and improve life quality.
