Larsen Syndrome
Larsen syndrome is a rare genetic disorder that has been associated with a wide variety of different symptoms. Characteristic findings of the disorder include dislocations of the large joints, skeletal malformations, and distinctive facial and limb features.
Causes of Larsen Syndrome
The classic form of Larsen syndrome follows autosomal dominant inheritance.
Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease.
The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual.
The risk of passing the abnormal gene from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
Symptoms of Larsen Syndrome
The symptoms and severity of Larsen syndrome vary greatly, including between individuals belonging to the same family.
In one large family whose members had Larsen syndrome caused by one of the recurring mutations, some affected individuals have cleft palate and multiple large joint dislocations.
But others have no major anomalies and manifested only short stature and mild features, such as short distal phalanges (toe and fingertip bones) and extra bones in the wrist and ankle Mild short stature is common with height below the tenth percentile in 70% of the cases.
Skeletal and joint abnormalities with distinctive facial features are the most common findings associated with the classic, autosomal dominant Larsen syndrome.
Spine abnormalities occur in 84% of individuals with Larsen syndrome including abnormal sideways curvature of the spine (scoliosis) or front-to-back curvature of the spinal bones (vertebrae) in the neck (cervical kyphosis).
Individuals with Larsen also have distinctive facial features, which include eyes that are wider apart than normal (hypertelorism), prominent forehead, and depressed bridge of the nose.
A few individuals with classic Larsen syndrome have developed abnormal softening of the cartilage of the windpipe (trachea), a condition known as tracheomalacia, but more severe conditions associated with FLNB mutations, such as atelosteogenesis, can have severe laryngotrachiomalacia.
Diagnosis of Larsen Syndrome
The diagnosis of Larsen syndrome is made based upon a thorough clinical evaluation, detailed patient history, and identification of characteristic clinical and radiological findings.
Radiographic examination can detect the presence and severity of associated skeletal findings.
Molecular genetic testing can confirm the presence of the FLNB gene mutation.
Prenatal diagnosis of Larsen syndrome may be possible through ultrasound imaging, where reflected sound waves are used to create an image of the developing fetus and reveal characteristic findings based on the clinical experience of the sonographer.
Treatment of Larsen Syndrome
The treatment of Larsen syndrome is directed toward the specific symptoms that are apparent in each individual.
Treatment may require the coordinated efforts of a team of specialists.
Pediatricians, orthopedic surgeons, craniofacial specialists, and geneticists who assess and treat skeletal disorders, as well as other specialists who asses and treat hearing problems (audiologists) may need to systematically and comprehensively plan an affected child’s treatment.
Treatment of infants with Larsen syndrome consists of joint manipulation and corrective casts or traction.
Later, orthopedic surgery may be recommended to correct skeletal dislocations or deformities.
Physical therapy may be necessary to strengthen affected joints.
Treatment of joint abnormalities often requires long-term therapy.
Stabilization of the cervical spine may be necessary in some cases and may include spinal surgery such as the fusion of affected spinal bones.
Genetic counseling is recommended for affected individuals and their families. Other treatment is symptomatic and supportive.