Acromicric Dysplasia

A rare bone dysplasia characterized by short stature, short hands and feet, mild facial dysmorphism, and characteristic X-ray abnormalities of the hands.

Epidemiology

The prevalence is unknown. Fewer than 60 patients with this condition have been reported to date.

Clinical description

Length is usually normal at birth but postnatal height falls progressively below the normal percentiles. The mean adult height is 130 cm (133 cm in males, 129 cm in females). The hands, feet, and limbs are short and occipitofrontal circumference is normal. There is no intellectual deficit. Mild dysmorphic features have been noted, including a round face, narrow palpebral fissures, well-defined eyebrows, long eyelashes, a bulbous nose with anteverted nostrils, a long and prominent philtrum, and thick lips with a small mouth. Other features include well-developed muscles, a hoarse voice, generalized joint limitations in some patients, frequent ear, tracheal, and respiratory complications, and spine abnormalities. Long-term follow-up shows that facial dysmorphism becomes less obvious in adults and that carpal tunnel syndrome is frequent in older patients. The entity known as Moore-Federman syndrome (see this term) characterized by short stature (with disproportionately short legs), joint stiffness, ocular abnormalities (hypermetropia, glaucoma) and thickened skin on the forearms, is believed to represent a variable clinical expression of acromicric dysplasia.

Etiology

The disease is caused by heterozygous mutations in the FBN1 gene. Mutations are all located in exon 41-42, encoding TGFβ binding protein-like domain 5.

Diagnostic methods

Diagnosis of acromicric dysplasia can be suspected on association of severe postnatal short stature, short hands and feet, normal intelligence and mild facial dysmorphism. X-rays show delayed carpal bone age, cone shaped epiphyses, short metacarpals and phalanges with an internal notch of the second metacarpal, an external notch of the fifth metacarpal, as well as an internal notch of the femoral heads. Notches of the hands disappear in adulthood.

Differential diagnosis

Overlapping syndromes include geleophysic dysplasia, Weill-Marchesani syndrome, and Myhre syndrome (see these terms). Geleophysic dysplasia can be distinguished from acromicric dysplasia by the presence of cardiac abnormalities (e.g. cardiac valvular thickening), Weill-Marchesani syndrome by the presence of microspherophakia, and Myhre syndrome by the presence of prognathism, deafness, developmental delay, and a thick calvarium.

Genetic counseling

Transmission is autosomal dominant. Affected individuals have a 50% risk of transmitting the disease to their offspring.

Management and treatment

Orthopedic management may be needed for hip dysplasia during childhood and for carpal tunnel syndrome in older patients. Physical therapy is required to prevent progressive joint limitation. In a few cases, children have been treated with growth hormone therapy. Regular multidisciplinary follow-up is required, especially for respiratory abnormalities.

Prognosis

The prognosis for affected individuals is usually good with a normal life expectancy. However, complications may occur, such as respiratory disorders, which may worsen the prognosis.