Langer mesomelic dysplasia

Langer mesomelic dysplasia (LMD) is a rare congenital disorder characterized by an altered bone formation that causes a severe short and disproportionate stature.

Classification

It’s part of the mesomelic and rhizomelic skeletal dysplasias, primary bone diseases in which the short stature is due to a lack of complete bone development of the limb’s long bones. It’s strictly related to another disease, the Léri–Weill dyschondrosteosis, of which it seems to be the homozygothic variant, clinically more severe (it differs from this disorder for the absence, in some cases, of the Madelung deformity too).

Epidemiology

The incidence is less than 1/1.000.000. Less than 50 cases have been reported so far.

Pathogenesis

At the core of the disorder there is a homozygous or compound heterozygous mutation or deletion of the SHOX (Short Stature Homeobox), SHOXY (Short Stature Homeobox Y-linked) or PAR1 (where SHOX enhancer elements are located) genes, which is inherited in a pseudosomal recessive manner.

Symptoms and signs

Clinically and radiologically the disease is characterized by severe shortening of long bones (limb's both proximal and median segments are affected), aplasia or severe hypoplasia of ulna and fibula, thickened and curved radius and tibia. These anomalies can cause deformities of the hands and feet. Hypoplasia of the mandible can also be present.

Diagnosis

Diagnosis may be suspected on the basis of the clinical and radiologic findings, and can supported by molecular analysis of the SHOX, SHOXY and PAR1 genes. May also be suspected by ultrasound during the second trimester of gestation.

Treatment

There is no known cure. In selected patients orthopaedic surgery may be helpful to try to gain some functionality of severely impaired joints.

Prognosis

Life expectancy is normal.

Bibliography

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See also

• Osteochondrodysplasia