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At a glance

A disorder with mild facial anomalies, severe growth retardation, and marked shortening of hands and feet secondary to short and stubby metacarpals and -tarsals, and phalanges. Acromicric dysplasia belongs to the group of acromelic dysplasias, which also include ☞Geleophysic Dysplasia and ☞Weill-Marchesani Syndrome.

History

First described in six patients in 1986 by the French pediatrician Pierre Maroteaux and colleagues.

Incidence

Approximately 30 cases have been reported to date.

Genetic inheritance

Most cases seem to be sporadic, but vertical transmission has also been described. Both sexes are affected, thus an autosomal dominant mode of inheritance has been postulated for the nonsporadic cases. The defect is caused by mutations in the Fibrillin-1 (FBN1) gene that has been mapped to chromosome 15q21.1 (mutations in the same FBN1-gene are also linked to ☞Marfan Syndrome). FBN1 is a major glycoprotein and part of microfibrils in the extracellular matrix that are involved in the properties of load-bearing connective tissues and the deposition of elastin in skin and vessels. The morphology of the growth cartilage appears disorganized with the cell columns replaced by ovoid or round groups of chondrocytes irregularly distributed, some close together and others separated by wide septa. Cell hypertrophy is found in the lower part of the cartilage and the invasion zone noted as being slightly irregular. Electron microscopy of the upper tibial growth cartilage shows many degenerating cells in various zones of the growth cartilage. Accumulation of glycogen and abnormal, disorganized collagen in the cell lacunae can be found throughout. In many areas of the interterritorial matrix, the collagen forms thick fibers of unequal diameter.

Diagnosis

Initially based on the clinical and radiological findings and confirmed by genetic testing. However, the birth length is most often normal and the growth delay becomes progressively apparent only in the second year of life.

Clinical aspects

These patients are of normal intelligence and other than the orthopedic issues are generally physically healthy. In some patients, however, an increased incidence of hoarse voice, otitis, upper airway infections, and asthma has been reported. The facial anomalies are mild, such as round face, narrow palpebral fissures with long eyelashes, well defined eyebrows, short, bulbous nose with anteverted nostrils, long philtrum, and thick lips with a small mouth. Facial dysmorphism becomes less evident once reaching teenage. Body length at birth is usually normal, but short stature is becoming progressively obvious after the first year of life. The typical orthopedic findings include an often muscular body build (in approximately 60% of patients), severe growth retardation with a mean adult height of 130 cm (133 cm in males, 129 cm in females), and marked shortening of hands and feet. Radiologic imaging reveals short, stubby metacarpals and phalanges with notching on the radial side of the second metacarpal ...

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