Acromicric Dysplasia is a condition characterized by severely short stature, short limbs, stiff joints, and distinctive facial features and an extremely rare inherited disorder characterized by abnormally short hands and feet, growth retardation, and delayed bone maturation leading to short stature, and mild facial abnormalities. Most cases have occurred randomly for no apparent reason (sporadically). However, autosomal dominant inheritance has not been ruled out.
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.
Causes
Acromicric Dysplasia is an extremely rare disorder that, in most cases, appears to occur randomly for no apparent reason (sporadically). However, autosomal dominant inheritance has not been ruled out.
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.
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.
Diagnosis
Acromicric Dysplasia may be diagnosed based on a thorough clinical evaluation, characteristic physical findings (e.g., abnormally shorthands), a detailed patient history, and a variety of specialized tests such as advanced imaging techniques. X-rays may reveal characteristic abnormalities of the bones in the hands and feet (e.g., abnormally short broad phalanges, metacarpals, and metatarsals; epiphyseal coning of the phalanges in the toes; pointing of the last four metacarpals, and the presence of an abnormal notch on the radial side of the 2nd metacarpal and ulnar side of the 5th metacarpal). The removal and study of cartilage cells (biopsy) under a microscope may reveal distinctive abnormalities affecting the growth of cartilage. These abnormalities may include disorganization of the “growing” portion of certain bones, especially abnormal organization of cells that form cartilage (chondrocytes) and of a protein substance (collagen) that forms fibers within the ligaments, tendons, and connective tissue. In addition, an abnormally high number of such cells may demonstrate degeneration.
Treatment
The treatment of Acromicric Dysplasia is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians, specialists who diagnose and treat skeletal abnormalities (orthopedists), physical therapists, and/or other health care professionals may need to systematically and comprehensively plan an affected child’s treatment.
Genetic counseling will be of benefit to affected individuals and their families. Another treatment for this disorder is symptomatic and supportive.
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