Aliases: Giedion-Langer syndrome, trichorhinophalangeal syndrome type II (TRPS II), Multiple exostoses.
Gene(s) involved: EXT1 and TRPS1 located on chromosome 8q24.1.
Brief description of disorder: Langer-Giedion syndrome (LGS) is characterized by multiple exostoses, sparse hair, loose skin in infancy, and characteristic facies. Typical facial characteristics include a bulbous nose, broad nasal bridge, large protruding ears, long philtrum, thin upper lip, deep set eyes, and heavy eyebrows. Other findings include lax joints, hypotonia, mild growth deficiency, scoliosis, dental anomalies, and recurrent upper respiratory infections. Nearly 70% of affected individuals may exhibit mild to severe mental retardation. Delayed speech and sensorineural hearing loss have also been reported. Thin, hypomineralized bones may lead to a tendency to fracture.
The prevalence of LGS is unknown.
Inheritance pattern: LGS is inherited in an autosomal dominant manner. Most cases are caused by de novo genetic deletions.
Genetics: LGS is a contiguous gene deletion syndrome caused by deletions involving EXT1 and TRPS1 genes. Larger deletions are associated with mental retardation. Conventional cytogenetic analysis, FISH, and array will detect deletions causative of LGS most of the time.
Test method: Conventional cytogenetic analysis, FISH, and array.
Test sensitivity: Cytogenetic analysis detects approximately 25% of deletions that are greater than 5 Mb. FISH and array will detect 98-100% of deletions/ duplications; however, deletions/ duplications smaller than 100 kb will not be detected on array and deletions/ duplications smaller than the FISH probe will not be detected by FISH.
Specimen requirements for Cytogenetic Analysis, FISH, and Array:
Adult: 3-5 ml peripheral blood in a sodium-heparin tube.
Newborn: 1-3 ml blood in a sodium-heparin tubee.
Turn-around-time:
Newborns: 2-3 days
Non-STAT: 2-14 days
FISH: 6-8 days
Array: 7-14 days
References: Genetics Home Reference
revised 5-24-2011
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