Boomerang dysplasia

Boomerang dysplasia
Other names	Dwarfism with short, bowed, rigid limbs and characteristic facies
Boomerang dysplasia has an autosomal dominant pattern of inheritance.
Specialty	Medical genetics

Boomerang dysplasia is a lethal form of

Osteochondrodysplasias are skeletal disorders that cause malformations of both bone and cartilage.

Presentation

Prenatal and neonatal diagnosis of boomerang dysplasia includes several prominent features found in other osteochondrodysplasias, though the "boomerang" malformation seen in the long bones is the delineating factor.^[2]

Featured symptoms of boomerang dysplasia include: dwarfism^[3] (a lethal type of infantile dwarfism caused by systemic bone deformities),^[4] underossification (lack of bone formation) in the limbs, spine and ilium (pelvis);^[1] proliferation of multinucleated giant-cell chondrocytes (cells that produce cartilage and play a role in skeletal development - chondrocytes of this type are rarely found in osteochondrodysplasias),^[5] brachydactyly (shortened fingers) and micromelia (undersized, shortened bones).^[2]

The characteristic "boomerang" malformation presents intermittently among random absences of long bones throughout the skeleton, in affected individuals.^[3][6] For example, one individual may have an absent radius and fibula, with the "boomerang" formation found in both ulnas and tibias.^[6] Another patient may present "boomerang" femora, and an absent tibia.^[3]

Cause

Mutations in the Filamin B (FLNB) gene cause boomerang dysplasia.^[1] FLNB is a cytoplasmic protein that regulates intracellular communication and signalling by cross-linking the protein actin to allow direct communication between the cell membrane and cytoskeletal network, to control and guide proper skeletal development.^[7] Disruptions in this pathway, caused by FLNB mutations, result in the bone and cartilage abnormalities associated with boomerang dysplasia.^{[citation needed]}

Chondrocytes, which also have a role in bone development, are susceptible to these disruptions and either fail to undergo ossification, or ossify incorrectly.^[1][7]

FLNB mutations are involved in a spectrum of lethal bone dysplasias. One such disorder, atelosteogenesis type I, is very similar to boomerang dysplasia, and several symptoms of both often overlap.^[8][9]

Genetics

Early journal reports of boomerang dysplasia suggested

Autosomal dominant inheritance indicates that the defective gene responsible for a disorder is located on an autosome, and only one copy of the gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.^[10]

Boomerang dysplasia, although an autosomal dominant disorder,^[8] is not inherited because those afflicted do not live beyond infancy.^[1] They cannot pass the gene to the next generation.^{[citation needed]}

Diagnosis

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Treatment

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See also

• Larsen syndrome

References