Weissenbacher-Zweymuller Synd... Health Article

Definition

Weissenbacher-Zweymuller syndrome (WZS) is a genetic form of dwarfism in which affected individuals are born with small, underdeveloped jaws (micrognathia), cleft palate, short arms and legs (rhizomelia), "dumbbell" shaped arm and leg bones, protruding wide spaced eyes (hypertelorism), and incompletely formed back bones (vertebral coronal clefts). Unlike most other forms of dwarfism, individuals affected by Weissebacher-Zweymuller start out being affected by dwarfism and then have a period of gradual growth and bone change that leads to normal physical development by five or six years of age.

Description

Weissenbacher-Zweymuller syndrome refers to a rare disorder of small underdeveloped jaws (micrognathia), delayed bone growth, and unusual bone formation first described in 1964 by Weissenbacher and Zweymuller. The formation of bones is delayed because an important structural component of bone called cartilage does not form correctly. Since bone development is delayed, early milestones like walking and physical growth are delayed. Due to cleft palate, many individuals affected by WZS have speech and language delays. In most cases, physical, motor, mental, and academic development is normal by five or six years of age. Alternate names sometimes used for WZS include Pierre Robin syndrome with fetal chondrodysplasia and heterozygous otospondy lome gaepiphyseal dysplasia (OSMED).

Genetic profile

Weissenbacher-Zweymuller syndrome appears to be caused by a single change or mutation in a gene called COL11A2 located on the short arm of chromosome 6. The mutation in COL11A2 leads to the incorrect formation of collagen. Since collagen is an important structural part of cartilage and bone, a mutation in COL11A2 leads to the signs and symptoms of WZS. The specific mutation that leads to WZS is inherited in an autosomal recessive pattern. An autosomal recessive condition is caused by the inheritance of two abnormal copies of a gene.

In the 1970s and 1980s there was some confusion among geneticists who were uncertain if WZS is a separate syndrome or part of another genetic syndrome. Although this confusion is not completely resolved, in 1993 an important study compared WZS to other related genetic syndromes and concluded that WZS is a separate genetic disorder that should not be "lumped" into the category of other genetic syndromes like Stickler syndrome. Since that time, a 1998 genetic study found that WZS and another syndrome called otospondylomegaepiphyseal dysplasia (OSMED) appear to be caused by different mutations in the same gene. This finding led the authors to suggest that the term OSMED be used to encompass a broad category that includes WZS as "heterozygous" OSMED while the other syndrome now called OSMED should be called "homozygous" OSMED. Because it has been found that WZS results from both heterozygous and homozygous mutations, researchers have suggested that this disorder follows both autosomal dominant and autosomal recessive inheritance patterns.