Boomerang Dysplasia

Boomerang dysplasia (BD) is a rare lethal skeletal dysplasia characterized by severe short-limbed dwarfism, dislocated joints, club feet, distinctive facies and diagnostic x-ray findings of underossified and dysplastic long tubular bones, with a boomerang-like bowing.

Epidemiology

The prevalence of BD is unknown.

Clinical description

Affected neonates are stillborn or die rapidly after birth and present clinically with severe short-limbed dwarfism, dislocated hip, knee and elbow joints, club feet and proviso born alive have severe cardio respiratory failure. Facial dysmorphism includes midface hypoplasia and cleft palate. Boomerang dysplasia clinically differs from AOI and AOIII because of the boomerang shaped bowing of the femur and occasionally observed encephalocele and omphalocele.

Etiology

BD results from missense mutations or small in-frame deletions in the FLNB gene reported in exons 2-5, normally expected to translate full length but biochemically abnormal filamin B protein.

Diagnostic methods

Diagnosis can be confirmed from skeletal radiographs, chondro-osseous histopathology and genetic testing. Distinctive radiographic findings are similar to AOI but, BD presents with a more severe deficiency in mineralization, with non-ossification of certain segments of limbs and vertebrates, and a boomerang-like shape of some long tubular bones.

Differential diagnosis

Comprises other skeletal dysplasias with severe short-limbed dwarfism such as achondrogenesis, campomelic dysplasia, Ellis-van Creveld syndrome, achondroplasia, metatropic dysplasia, Roberts syndrome, short rib-polydactyly syndrome and thanatophoric dysplasia. Additional differential diagnosis includes diseases associated with impaired ossification such achondrogenesis, hypophosphatasia, and osteogenesis imperfecta (see these terms).

Antenatal diagnosis

The prenatal diagnosis of BD is difficult to ascertain by ultrasound. Ultrasound shows thoracic hypoplasia, limb shortening, delayed ossification of spine and appendicular segments and possibly joint dislocations, similar to AOI and AOIII. Boomerang-shape morphology some long tubular bones may be diagnosed prenatally by 3D-CT scan.

Prognosis

Prognosis is poor, as the condition is lethal in utero.